248 results on '"Ya-Hong Xie"'
Search Results
2. Gold Nanopyramid Arrays for Non-Invasive Surface-Enhanced Raman Spectroscopy-Based Gastric Cancer Detection via sEVs
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Zirui Liu, Tieyi Li, Zeyu Wang, Jun Liu, Shan Huang, Byoung Hoon Min, Ji Young An, Kyoung Mee Kim, Sung Kim, Yiqing Chen, Huinan Liu, Yong Kim, David T.W. Wong, Tony Jun Huang, and Ya-Hong Xie
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General Materials Science - Abstract
Gastric cancer (GC) is one of the most common and lethal types of cancer affecting over one million people, leading to 768,793 deaths globally in 2020 alone. The key for improving the survival rate lies in reliable screening and early diagnosis. Existing techniques including barium-meal gastric photofluorography and upper endoscopy can be costly and time-consuming and are thus impractical for population screening. We look instead for small extracellular vesicles (sEVs, currently also referred as exosomes) sized ⌀ 30-150 nm as a candidate. sEVs have attracted a significantly higher level of attention during the past decade or two because of their potentials in disease diagnoses and therapeutics. Here, we report that the composition information of the collective Raman-active bonds inside sEVs of human donors obtained by surface-enhanced Raman spectroscopy (SERS) holds the potential for non-invasive GC detection. SERS was triggered by the substrate of gold nanopyramid arrays we developed previously. A machine learning-based spectral feature analysis algorithm was developed for objectively distinguishing the cancer-derived sEVs from those of the non-cancer sub-population. sEVs from the tissue, blood, and saliva of GC patients and non-GC participants were collected (
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- 2022
3. Ohmic Contact to p-Type GaN Enabled by Post-Growth Diffusion of Magnesium
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Wentao Cai, Hiroshi Amano, Takeru Kumabe, Yoshio Honda, Jia Wang, Yuto Ando, Shun Lu, Ya-Hong Xie, and Yaqiang Liao
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Materials science ,Magnesium ,business.industry ,chemistry.chemical_element ,Plasma ,Electronic, Optical and Magnetic Materials ,chemistry ,Electrical resistivity and conductivity ,Optoelectronics ,Electrical and Electronic Engineering ,Current (fluid) ,Diffusion (business) ,business ,Ohmic contact ,Diode - Abstract
We demonstrated 1 the formation of excellent Ohmic contact to p-type GaN (including the plasma etching-damaged p-type GaN which otherwise exhibited undetectable current within 15V) by the post-growth diffusion of magnesium. The specific contact resistivity on the order of 10-4 Ω.cm2 (extracted at V=0V) was achieved on the plasma-damaged p-GaN with linear current-voltage characteristics by the transfer length method (TLM) measurement. The improvement in current by a factor of over 109 was also obtained on the plasma-damaged p-n junction diode after the same Mg-treatment. These experimental results indicate a great potential of post-growth diffusion of Mg to overcome the bottleneck of forming a good Ohmic contact to p-GaN.
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- 2022
4. Analyzing bronchoalveolar fluid derived small extracellular vesicles using single-vesicle SERS for non-small cell lung cancer detection
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Sumita T. Jonak, Zirui Liu, Jun Liu, Tieyi Li, Brian V. D'Souza, J. Alan Schiaffino, Scott Oh, and Ya-Hong Xie
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Detection ,screening and diagnosis ,Clinical Research ,Lung Cancer ,Lung ,Cancer ,4.2 Evaluation of markers and technologies ,4.1 Discovery and preclinical testing of markers and technologies - Abstract
An emerging body of research by biologists and clinicians has demonstrated the clinical application of small extracellular vesicles (sEVs, also commonly referred to as exosomes) as biomarkers for cancer detections. sEVs isolated from various body fluids such as blood, saliva, urine, and cerebrospinal fluid have been used for biomarker discoveries with highly encouraging outcomes. Among the biomarkers discovered are those responsible for multiple cancer types and immune responses. These biomarkers are recapitulated from the tumor microenvironments. Yet, despite numerous discussions of sEVs in scientific literature, sEV-based biomarkers have so far played only a minor role for cancer diagnostics in the clinical setting, notably less so than other techniques such as imaging and biopsy. In this paper, we report the results of a pilot study (n = 10 from each of the patient and the control group) using bronchoalveolar lavage fluid to determine the presence of sEVs related to non-small cell lung cancer in twenty clinical samples examined using surface enhanced Raman spectroscopy (SERS).
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- 2023
5. Multiwavelength High-Detectivity MoS
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Yanxiao, Sun, Luyue, Jiang, Zhe, Wang, Zhenfei, Hou, Liyan, Dai, Yankun, Wang, Jinyan, Zhao, Ya-Hong, Xie, Libo, Zhao, Zhuangde, Jiang, Wei, Ren, and Gang, Niu
- Abstract
Photodetection is one of the vital functions for the multifunctional "More than Moore" (MtM) microchips urgently required by Internet of Things (IoT) and artificial intelligence (AI) applications. The further improvement of the performance of photodetectors faces various challenges, including materials, fabrication processes, and device structures. We demonstrate in this work MoS
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- 2022
6. Design, Fabrication and Characterization of Single-Crystalline Graphene gNEMS ESD Switches for Future ICs
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Kun Zhang, Jimmy Ng, Albert Wang, Feilong Zhang, Qi Chen, Tianru Wu, Ya-Hong Xie, Xiaoming Xie, Cheng Li, Mengfu Di, Han Wang, and Zijin Pan
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010302 applied physics ,Fabrication ,Electrostatic discharge ,Materials science ,Silicon ,Graphene ,business.industry ,Overhead (engineering) ,chemistry.chemical_element ,Integrated circuit ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,law.invention ,CMOS ,chemistry ,law ,0103 physical sciences ,Optoelectronics ,Electrical and Electronic Engineering ,Safety, Risk, Reliability and Quality ,business ,Transmission-line pulse - Abstract
On-chip electrostatic discharge (ESD) protection is becoming more challenging for integrated circuits (ICs) made in advanced technology nodes. The ESD-induced design overhead, including ESD parasitic effects and layout area, inherent to the traditional in-Silicon PN-junction-based ESD protection devices, rapidly becomes unbearable to high-performance and complex ICs. A disruptive above-Si mechanical ESD switch device, made in CMOS backend using a graphene nano-electromechanical-system (gNEMS) structure, was recently devised and demonstrated using poly-crystalline graphene films. This paper reports design, fabrication and comprehensive characterization of single-crystalline gNEMS ESD switch devices. Measurement using transmission line pulse (TLP) and very fast transmission line pulse (VFTLP) ESD testing reveals superior ESD protection capability of gNEMS devices made in single-crystalline graphene over its poly-crystalline counterparts, achieving a record-high ESD current handling capability of ${\text{I}}_{t2} {\sim }1.19 {\times }10^{10}\text{A}$ /cm2 under TLP zapping and ${\text{I}}_{t2} {\sim }6.09{\times }10^{9}\text{A}$ /cm2 under VFTLP stressing. The ESD robustness enhancement related to single-crystalline graphene material property is discussed.
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- 2021
7. Phase 2 of extracellular RNA communication consortium charts next-generation approaches for extracellular RNA research
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Bogdan Mateescu, Jennifer C. Jones, Roger P. Alexander, Eric Alsop, Ji Yeong An, Mohammad Asghari, Alex Boomgarden, Laura Bouchareychas, Alfonso Cayota, Hsueh-Chia Chang, Al Charest, Daniel T. Chiu, Robert J. Coffey, Saumya Das, Peter De Hoff, Andrew deMello, Crislyn D’Souza-Schorey, David Elashoff, Kiarash R. Eliato, Jeffrey L. Franklin, David J. Galas, Mark B. Gerstein, Ionita H. Ghiran, David B. Go, Stephen Gould, Tristan R. Grogan, James N. Higginbotham, Florian Hladik, Tony Jun Huang, Xiaoye Huo, Elizabeth Hutchins, Dennis K. Jeppesen, Tijana Jovanovic-Talisman, Betty Y.S. Kim, Sung Kim, Kyoung-Mee Kim, Yong Kim, Robert R. Kitchen, Vaughan Knouse, Emily L. LaPlante, Carlito B. Lebrilla, L. James Lee, Kathleen M. Lennon, Guoping Li, Feng Li, Tieyi Li, Tao Liu, Zirui Liu, Adam L. Maddox, Kyle McCarthy, Bessie Meechoovet, Nalin Maniya, Yingchao Meng, Aleksandar Milosavljevic, Byoung-Hoon Min, Amber Morey, Martin Ng, John Nolan, Getulio P. De Oliveira Junior, Michael E. Paulaitis, Tuan Anh Phu, Robert L. Raffai, Eduardo Reátegui, Matthew E. Roth, David A. Routenberg, Joel Rozowsky, Joseph Rufo, Satyajyoti Senapati, Sigal Shachar, Himani Sharma, Anil K. Sood, Stavros Stavrakis, Alessandra Stürchler, Muneesh Tewari, Juan P. Tosar, Alexander K. Tucker-Schwartz, Andrey Turchinovich, Nedyalka Valkov, Kendall Van Keuren-Jensen, Kasey C. Vickers, Lucia Vojtech, Wyatt N. Vreeland, Ceming Wang, Kai Wang, ZeYu Wang, Joshua A. Welsh, Kenneth W. Witwer, David T.W. Wong, Jianping Xia, Ya-Hong Xie, Kaichun Yang, Mikołaj P. Zaborowski, Chenguang Zhang, Qin Zhang, Angela M. Zivkovic, and Louise C. Laurent
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Biological sciences ,Cell biology ,Multidisciplinary ,Molecular biology ,FOS: Biological sciences ,Biochemistry ,Human Genome ,Genetics - Abstract
The extracellular RNA communication consortium (ERCC) is an NIH-funded program aiming to promote the development of new technologies, resources, and knowledge about exRNAs and their carriers. After Phase 1 (2013-2018), Phase 2 of the program (ERCC2, 2019-2023) aims to fill critical gaps in knowledge and technology to enable rigorous and reproducible methods for separation and characterization of both bulk populations of exRNA carriers and single EVs. ERCC2 investigators are also developing new bioinformatic pipelines to promote data integration through the exRNA atlas database. ERCC2 has established several Working Groups (Resource Sharing, Reagent Development, Data Analysis and Coordination, Technology Development, nomenclature, and Scientific Outreach) to promote collaboration between ERCC2 members and the broader scientific community. We expect that ERCC2's current and future achievements will significantly improve our understanding of exRNA biology and the development of accurate and efficient exRNA-based diagnostic, prognostic, and theranostic biomarker assays., iScience, 25 (8), ISSN:2589-0042
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- 2022
8. Hybrid System Combining Two-Dimensional Materials and Ferroelectrics and Its Application in Photodetection
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Wenbo Luo, Wei Ren, Xiangjian Meng, Ya-Hong Xie, Jinyan Zhao, Gang Niu, Yanxiao Sun, and Zuo-Guang Ye
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Computer science ,business.industry ,Transistor ,General Engineering ,General Physics and Astronomy ,Photodetector ,Schottky diode ,02 engineering and technology ,Photodetection ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Engineering physics ,Ferroelectricity ,0104 chemical sciences ,law.invention ,Semiconductor ,law ,Hybrid system ,General Materials Science ,0210 nano-technology ,business ,Diode - Abstract
Photodetectors are one of the most important components for a future "Internet-of-Things" information society. Compared to the mainstream semiconductor-based photodetectors, emerging devices based on two-dimensional (2D) materials and ferroelectrics as well as their hybrid systems have been extensively studied in recent decades due to their outstanding performances and related interesting physical, electrical, and optoelectronic phenomena. In this paper, we review the photodetection based on 2D materials and ferroelectric hybrid systems. The fundamentals of 2D and ferroelectric materials as well as the interaction in the hybrid system will be introduced. Ferroelectricity modulated optoelectronic properties in the hybrid system will be discussed in detail. After the basics and figures of merit of photodetectors are summarized, the 2D-ferroelectrics devices with different structures including p-n diodes, Schottky diodes, and field-effect transistors will be reviewed and compared. The polarization of ferroelectrics offers the possibility of the modulation and enhancement of the photodetection in the hybrid detectors, which will be discussed in depth. Finally, the challenges and perspectives of the photodetectors based on 2D ferroelectrics will be proposed. This Review outlines the important aspects of the recent development of the hybrid system of 2D and ferroelectric materials, which could interact with each other and thus lead to photodetectors with higher performances. Such a Review will be helpful for the research of emerging physical phenomena and for the design of multifunctional nanoscale electronic and optoelectronic devices.
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- 2021
9. The Feasibility of Early Alzheimer's Disease Diagnosis Using a Neural Network Hybrid Platform
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Xinke Yu, Siddharth Srivastava, Shan Huang, Eric Y. Hayden, David B. Teplow, and Ya-Hong Xie
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Clinical Biochemistry ,Biomedical Engineering ,Reproducibility of Results ,General Medicine ,Analytical Chemistry ,SERS ,Alzheimer’s disease ,biosensing ,Raman spectroscopy ,machine learning ,neural networks ,disease diagnosis ,materials science ,nanomaterials ,Early Diagnosis ,Alzheimer Disease ,Feasibility Studies ,Humans ,Neural Networks, Computer ,Instrumentation ,Engineering (miscellaneous) ,Biomarkers ,Biotechnology - Abstract
Early diagnosis of Alzheimer’s Disease (AD) is critical for disease prevention and cure. However, currently, techniques with the required high sensitivity and specificity are lacking. Recently, with the advances and increased accessibility of data analysis tools, such as machine learning, research efforts have increasingly focused on using these computational methods to solve this challenge. Here, we demonstrate a convolutional neural network (CNN)-based AD diagnosis approach using the surface-enhanced Raman spectroscopy (SERS) fingerprints of human cerebrospinal fluid (CSF). SERS and CNN were combined for biomarker detection to analyze disease-associated biochemical changes in the CSF. We achieved very high reproducibility in double-blind experiments for testing the feasibility of our system on human samples. We achieved an overall accuracy of 92% (100% for normal individuals and 88.9% for AD individuals) based on the clinical diagnosis. Further, we observed an excellent correlation coefficient between our test score and the Clinical Dementia Rating (CDR) score. Our findings offer a substantial indication of the feasibility of detecting AD biomarkers using the innovative combination of SERS and machine learning. We are hoping that this will serve as an incentive for future research in the field.
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- 2022
10. Highly heterogeneous epitaxy of flexoelectric BaTiO3-δ membrane on Ge
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Liyan Dai, Jinyan Zhao, Jingrui Li, Bohan Chen, Shijie Zhai, Zhongying Xue, Zengfeng Di, Boyuan Feng, Yanxiao Sun, Yunyun Luo, Ming Ma, Jie Zhang, Sunan Ding, Libo Zhao, Zhuangde Jiang, Wenbo Luo, Yi Quan, Jutta Schwarzkopf, Thomas Schroeder, Zuo-Guang Ye, Ya-Hong Xie, Wei Ren, and Gang Niu
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Multidisciplinary ,General Physics and Astronomy ,General Chemistry ,General Biochemistry, Genetics and Molecular Biology - Abstract
The integration of complex oxides with a wide spectrum of functionalities on Si, Ge and flexible substrates is highly demanded for functional devices in information technology. We demonstrate the remote epitaxy of BaTiO3 (BTO) on Ge using a graphene intermediate layer, which forms a prototype of highly heterogeneous epitaxial systems. The Ge surface orientation dictates the outcome of remote epitaxy. Single crystalline epitaxial BTO3-δ films were grown on graphene/Ge (011), whereas graphene/Ge (001) led to textured films. The graphene plays an important role in surface passivation. The remote epitaxial deposition of BTO3-δ follows the Volmer-Weber growth mode, with the strain being partially relaxed at the very beginning of the growth. Such BTO3-δ films can be easily exfoliated and transferred to arbitrary substrates like Si and flexible polyimide. The transferred BTO3-δ films possess enhanced flexoelectric properties with a gauge factor of as high as 1127. These results not only expand the understanding of heteroepitaxy, but also open a pathway for the applications of devices based on complex oxides.
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- 2022
11. An integration design model for a large-scale negative ion accelerator of neutral beam injection system for fusion application
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Jiang-Long Wei, Yu-Wen Yang, Yu-Ming Gu, Qing-Long Cui, Li-Zhen Liang, Cai-Chao Jiang, Yuan-Lai Xie, Ya-Hong Xie, and Chun-Dong Hu
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Condensed Matter Physics - Abstract
Design processes of a large-scale negative ion accelerator for neutral beam injection (NBI) application involve a series of physics and engineering issues, which include high voltage holding, background gas and stripping losses, beamlets optics and steering, particle and power flux on the grid electrodes, heat removal, thermal deformation, and stress of the grids. A self-consistent design model covering all these critical issues has been developed, where the results of one design aspect can be directly plugged into another one as the input conditions with little approximation or assumption. This design model has been applied to the negative ion accelerator of the NBI test facility of CRAFT (Comprehensive Research Facility for Fusion Technology), which is designed to produce a negative hydrogen ion beam of 25 A with the particle energy of 400 keV and the pulse duration of 3600 s. The accelerated current density is required to be 210 A/m2 from 768 apertures with a diameter of 14 mm. The evaluated results of the CRAFT accelerator design are quantitatively analyzed. Additionally, the modeling is applied to a large-scale and relatively complete structure of the multi-grid electrodes. Hence, some nonuniformities or special distributions appear in different design issues, which were not noticed in the reference works.
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- 2023
12. A Review of Surface-Enhanced Raman Spectroscopy on Potential Clinical Applications Towards Diagnosing Colorectal Cancer
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Owen Liang and Ya-Hong Xie
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Colorectal cancer ,business.industry ,medicine ,Cancer research ,Cancer ,Surface-enhanced Raman spectroscopy ,medicine.disease ,business - Published
- 2021
13. Toward a Reliable Synaptic Simulation Using Al-Doped HfO2 RRAM
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Yankun Wang, Zhitang Song, Peng Shi, Wenbo Luo, Zuo-Guang Ye, Christian Wenger, Qiang Wang, Thomas Schroeder, Ya-Hong Xie, Yijun Zhang, Wu Heping, Sannian Song, Sourav Roy, Gang Niu, Wei Ren, Shijie Zhai, and Xiangjian Meng
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010302 applied physics ,Materials science ,business.industry ,Annealing (metallurgy) ,Doping ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Resistive random-access memory ,X-ray photoelectron spectroscopy ,Neuromorphic engineering ,Transmission electron microscopy ,Resistive switching ,0103 physical sciences ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business - Abstract
The potential in a synaptic simulation for neuromorphic computation has revived the research interest of resistive random access memory (RRAM). However, novel applications require reliable multilevel resistive switching (RS), which still represents a challenge. We demonstrate in this work the achievement of reliable HfO2-based RRAM devices for synaptic simulation by performing the Al doping and the postdeposition annealing (PDA). Transmission electron microscopy and operando hard X-ray photoelectron spectroscopy results reveal the positive impact of Al doping on the formation of oxygen vacancies. Detailed I–V characterizations demonstrate that the 16.5% Al doping concentration leads to better RS properties of the device. In comparison with the other reported results based on HfO2 RRAM, our devices with 16.5% Al-doping and PDA at 450 °C show better reliable multilevel RS (∼20 levels) performance and an increased on/off ratio. The 16.5% Al:HfO2 sample with PDA at 450 °C shows good potentiation/depression ch...
- Published
- 2020
14. Toward van der Waals epitaxy of transferable ferroelectric barium titanate films via a graphene monolayer
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Wu Heping, Zuo-Guang Ye, Yiwei Liu, Gang Niu, Lingyan Wang, Daniel Pfützenreuter, Yankun Wang, Liyan Dai, Thomas Schroeder, Yijun Zhang, Wei Ren, Catherine Dubourdieu, Jinyan Zhao, Jutta Schwarzkopf, Huifeng Zhao, and Ya-Hong Xie
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Materials science ,Graphene ,business.industry ,Oxide ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Ferroelectricity ,Piezoelectricity ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Barium titanate ,Materials Chemistry ,Optoelectronics ,Crystallization ,0210 nano-technology ,business ,Layer (electronics) ,Perovskite (structure) - Abstract
Future “Internet of Things” requires transferable ferroelectric thin films for functional devices like sensors and actuators. We report here the growth of a typical ferroelectric perovskite compound, BaTiO3, on a graphene monolayer which remains intact during the oxide growth process at high temperatures and at elevated oxygen pressure. The graphene facilitates the crystallization of BaTiO3. The growth of BaTiO3 on the graphene monolayer is found to follow the Volmer–Weber mode with the formation of three dimensional islands at the initial growth stage. Highly (001)-oriented BaTiO3 crystalline films are fabricated and can be easily exfoliated using a metal stressor layer. The graphene monolayer remains attached to the exfoliated BaTiO3 film which demonstrates good piezoelectric properties. These results not only demonstrate the possibility to fabricate high quality crystalline ferroelectric films via a graphene monolayer, but also open the pathway to realize van der Waals epitaxy ferroelectric films which can be transferred onto arbitrary substrates, particularly onto flexible substrates for wearable devices applications.
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- 2020
15. Highly heterogeneous epitaxy of flexoelectric BaTiO
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Liyan, Dai, Jinyan, Zhao, Jingrui, Li, Bohan, Chen, Shijie, Zhai, Zhongying, Xue, Zengfeng, Di, Boyuan, Feng, Yanxiao, Sun, Yunyun, Luo, Ming, Ma, Jie, Zhang, Sunan, Ding, Libo, Zhao, Zhuangde, Jiang, Wenbo, Luo, Yi, Quan, Jutta, Schwarzkopf, Thomas, Schroeder, Zuo-Guang, Ye, Ya-Hong, Xie, Wei, Ren, and Gang, Niu
- Abstract
The integration of complex oxides with a wide spectrum of functionalities on Si, Ge and flexible substrates is highly demanded for functional devices in information technology. We demonstrate the remote epitaxy of BaTiO
- Published
- 2022
16. Approaching the Collection Limit in Hot Electron Transistors with Ambipolar Hot Carrier Transport
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Lingfei Li, Khurram Shehzad, Bin Yu, Ya-Hong Xie, Whenchao Chen, Xiaomu Wang, Wei Liu, Srikrishna Chanakya Bodepudi, Yang Xu, Hongwei Guo, and Akeel Qadir
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Materials science ,Chemical substance ,Ambipolar diffusion ,business.industry ,Graphene ,General Engineering ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,symbols.namesake ,Nanoelectronics ,law ,symbols ,Optoelectronics ,General Materials Science ,van der Waals force ,0210 nano-technology ,Spectroscopy ,business ,Saturation (magnetic) ,Current density - Abstract
Hot electron transistors (HETs) containing two-dimensional (2D) materials promise great potential in high-frequency analog and digital applications. Here, we experimentally demonstrate all-2D van der Waals (vdW) HETs formed by graphene, hBN, and WSe2, in which the polarity of carriers could be tuned by changing bias conditions. We proposed a theoretical model to distinguish hot hole and hot electron components in the ambipolar vdW HET. Importantly, both hot hole and hot electron modes are achieved with pronounced saturation behavior as well as record-high collection efficiency approaching theoretical limits (99.9%) at room temperature. The vdW HETs show a maximum output current density of 400 A/cm2. The observed ambipolar hot carrier transport with high collection efficiency is promising for high-speed nanoelectronics and 2D hot electron spectroscopy.
- Published
- 2019
17. Interfacial States and Fano–Feshbach Resonance in Graphene–Silicon Vertical Junction
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Xiang Zhang, Kang L. Wang, Shiao-Po Tsai, Zehua Jin, Wei-Hsiang Lin, Xiaodan Zhu, Shin Hung Tsai, Pulickel M. Ajayan, Zhongpo Zhou, Gen Yin, Jimmy Ng, Hussam Qasem, Xiaoyu Che, Robert Vajtai, Sidong Lei, Ya-Hong Xie, Peng Deng, and Nai-Chang Yeh
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Physics ,Condensed matter physics ,Silicon ,Graphene ,Mechanical Engineering ,chemistry.chemical_element ,Bioengineering ,Heterojunction ,Charge (physics) ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,law.invention ,chemistry ,law ,Quantum state ,General Materials Science ,0210 nano-technology ,Feshbach resonance ,Quantum ,Spin-½ - Abstract
Interfacial quantum states are drawing tremendous attention recently because of their importance in design of low-dimensional quantum heterostructures with desired charge, spin, or topological properties. Although most studies of the interfacial exchange interactions were mainly performed across the interface vertically, the lateral transport nowadays is still a major experimental method to probe these interactions indirectly. In this Letter, we fabricated a graphene and hydrogen passivated silicon interface to study the interfacial exchange processes. For the first time we found and confirmed a novel interfacial quantum state, which is specific to the 2D-3D interface. The vertically propagating electrons from silicon to graphene result in electron oscillation states at the 2D-3D interface. A harmonic oscillator model is used to explain this interfacial state. In addition, the interaction between this interfacial state (discrete energy spectrum) and the lateral band structure of graphene (continuous energy spectrum) results in Fano-Feshbach resonance. Our results show that the conventional description of the interfacial interaction in low-dimensional systems is valid only in considering the lateral band structure and its density-of-states and is incomplete for the ease of vertical transport. Our experimental observation and theoretical explanation provide more insightful understanding of various interfacial effects in low-dimensional materials, such as proximity effect, quantum tunneling, etc. More important, the Fano-Feshbach resonance may be used to realize all solid-state and scalable quantum interferometers.
- Published
- 2019
18. The conversion of CuInS2/ZnS core/shell structure from type I to quasi-type II and the shell thickness-dependent solar cell performance
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Ya-Hong Xie, Hong Li, Zirui Liu, and Liwang Liu
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Thickness dependent ,Work (thermodynamics) ,Materials science ,business.industry ,Photovoltaic system ,Shell (structure) ,02 engineering and technology ,Carrier lifetime ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Biomaterials ,Core (optical fiber) ,Electron transfer ,Colloid and Surface Chemistry ,law ,Solar cell ,Optoelectronics ,0210 nano-technology ,business - Abstract
Colloidal quantum dots (QDs) have attracted a great amount of attention for their appealing optoelectronic properties. In this work, the CuInS2 (CIS)/ZnS core/shell QDs based on 4.3 nm cores with various layers of ZnS shell (0 to 10) were synthesized. With the sequential growth of a ZnS shell over a CIS core, the band alignment of core/shell QDs converts from a type I to quasi-type II structure. This conversion prolongs the carrier lifetime and affects the electron transfer rate (Ket) and electron transfer efficiency (ηET). A comparative study indicates that the photovoltaic performance of CIS based QDSCs can be markedly improved by optimizing the layers of ZnS shell. The highest photo conversion efficiency (PCE) of 2.07% is obtained at optimum ZnS thickness of about 1.55 nm. These results show tuning the thickness of shell to change the band alignment is an effective strategy to manipulate the carriers transportation behaviors and thus affect the PCE of CIS-based optoelectronic devices.
- Published
- 2019
19. Interface-engineered reliable HfO2-based RRAM for synaptic simulation
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Qiang Wang, Zuo-Guang Ye, Yankun Wang, Bai Wei, Peng Shi, Ya-Hong Xie, Zhitang Song, Sannian Song, Yijun Zhang, Wei Ren, Sourav Roy, Xiangjian Meng, Shijie Zhai, Gang Niu, Wu Heping, and Christian Wenger
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Random access memory ,Materials science ,business.industry ,chemistry.chemical_element ,Long-term potentiation ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Resistive random-access memory ,chemistry ,Power consumption ,Electrode ,Materials Chemistry ,Optoelectronics ,Analog memory ,0210 nano-technology ,business ,Tin - Abstract
Future synaptic simulation using resistance random access memory (RRAM) requires higher reliability and lower power consumption of the devices and understanding of the correlation of the materials with their multi-level resistance switching (RS) properties. Using O3 pretreatment on a TiN electrode, this work highlights the significant role of the interface in the enhancement of the reliability and the power consumption of HfO2-based RRAM devices. X-ray photoelectron spectroscopy investigations indicate increases of the TiON and TiO2 components with the augmentation of the number of O3 treatment cycles, which strongly impacts the RS properties of the Pt/HfO2/TiN devices. Optimal RS properties were obtained for 20 O3 pulse-pretreated devices, which were used to emulate biological synapses after an annealing process. Analog memory properties, including analog set and reset in DC mode and potentiation/depression based on two types of designed pulses, have been achieved. Finally, one of the biological synapse learning rules, spike-timing-dependent plasticity, was successfully emulated. These results, avoiding the conventional route based on dual-layer insulators, are of significance for synaptic simulation using interface-engineered single-layer HfO2 RRAM and further reveal the internal mechanism of HfO2-based electron synapses.
- Published
- 2019
20. 3D GaN Power Switching Electronics: A Revival of Interest in ELO
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Jia Wang, Ya-Hong Xie, and Hiroshi Amano
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010302 applied physics ,Materials science ,business.industry ,Transistor ,Gallium nitride ,02 engineering and technology ,Substrate (electronics) ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,Anode ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Power electronics ,0103 physical sciences ,Optoelectronics ,Electronics ,0210 nano-technology ,business ,Diode - Abstract
We reported the first-time utilization of ELO (epitaxial lateral overgrowth) GaN (gallium nitride) for power diodes. The undesired stage of coalescence related to ELO is avoided by virtue of a novel 3D device architecture built on the ELO GaN islands on foreign substrate which features pure-lateral p-n and n+ -n-junctions and electrodes lying on the opposing sidewalls of the island. Excellent electrical performance was demonstrated, revealing a strong potential of ELO GaN with 3D device architecture for power switching applications.
- Published
- 2021
21. Ultrasensitive amyloid β-protein quantification with high dynamic range using a hybrid graphene-gold surface-enhanced Raman spectroscopy platform
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Ya-Hong Xie, Owen Liang, Ming Xia, Eric Y. Hayden, Xinke Yu, David B. Teplow, Yu Bai, and Pu Wang
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Analyte ,Materials science ,Graphene ,business.industry ,010401 analytical chemistry ,Hot spot (veterinary medicine) ,02 engineering and technology ,Surface-enhanced Raman spectroscopy ,Orders of magnitude (numbers) ,021001 nanoscience & nanotechnology ,01 natural sciences ,Article ,0104 chemical sciences ,law.invention ,symbols.namesake ,law ,symbols ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,Raman spectroscopy ,Biosensor ,Spectroscopy ,Plasmon - Abstract
Surface enhanced Raman spectroscopy (SERS) holds great promise in biosensing because of its single-molecule, label-free sensitivity. We describe here the use of a graphene-gold hybrid plasmonic platform that enables quantitative SERS measurement. Quantification is enabled by normalizing analyte peak intensities to that of the graphene G peak. We show that two complementary quantification modes are intrinsic features of the platform, and that through their combined use, the platform enables accurate determination of analyte concentration over a concentration range spanning seven orders of magnitude. We demonstrate, using a biologically relevant test analyte, the amyloid β-protein (Aβ), a seminal pathologic agent of Alzheimer’s disease (AD), that linear relationships exist between (a) peak intensity and concentration at a single plasmonic hot spot smaller than 100 nm, and (b) frequency of hot spots with observable protein signals, i.e. the co-location of an Aβ protein and a hot spot. We demonstrate the detection of Aβ at a concentration as low as 10(−18) M after a single 20 μl aliquot of the analyte onto the hybrid platform. This detection sensitivity can be improved further through multiple applications of analyte to the platform and by rastering the laser beam with smaller step sizes.
- Published
- 2021
22. Crucial impact of hydrophobicity on the self-assembly of 2D colloidal crystals using Langmuir-Blodgett method
- Author
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Heping Wu, Wei Ren, Luyue Jiang, Owen Liang, Jinyan Zhao, Yangyang Liu, Ya-Hong Xie, and Gang Niu
- Published
- 2020
23. Toward van der Waals Epitaxy of Transferable Ferroelectric BaTiO3 Thin Films on Graphene
- Author
-
Liyan Dai, Jinyan Zhao, Huifeng Zhao, Yiwei Liu, Yankun Wang, Yijun Zhang, Heping Wu, Lingyan Wang, Daniel Pfützenreuter, Jutta Schwarzkopf, Catherine Dubourdieu, Thomas Schroeder, Zuo-Guang Ye, Ya-Hong Xie, Wei Ren, and Gang Niu
- Published
- 2020
24. Crucial Impact of Hydrophilicity on the Self-Assembled 2D Colloidal Crystals Using Langmuir-Blodgett Method
- Author
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Owen Liang, Liu Yangyang, Gang Niu, Jiang Luyue, Wei Ren, Ya-Hong Xie, Jinyan Zhao, and Wu Heping
- Subjects
Materials science ,Nanotechnology ,02 engineering and technology ,Surfaces and Interfaces ,Colloidal crystal ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,High coverage ,01 natural sciences ,Langmuir–Blodgett film ,0104 chemical sciences ,Electrochemistry ,General Materials Science ,0210 nano-technology ,Spectroscopy - Abstract
Large-scale close-packed two-dimensional (2D) colloidal crystal with high coverage is indispensable for various promising applications. The Langmuir-Blodgett (LB) method is a powerful technique to prepare 2D colloidal crystals. However, the self-assembly and movement of microspheres during the whole LB process are less analyzed. In this study, we clarify the crucial impact of hydrophilicity of the microspheres on their self-assembly in the LB process and on the properties of the prepared 2D colloidal crystals. The characteristic surface pressure-area isotherms of the microspheres have been analyzed and adjusted by only counting the quantity of the microspheres on the water surface, which leads to more accurate results. The critical surface pressures for hydrophilic and hydrophobic microspheres are about 61 and 46 mN/m, respectively. The decrease of the surface hydrophilicity of microspheres facilitates their self-assembly on the water surface, which further leads to higher coverage and less defects of the 2D colloidal crystals. A coverage of as high as 97% was obtained using hydrophobic microspheres. Entropy and intersphere capillary forces drive the self-assembly and transportation of the microspheres, respectively. Caused by the diffraction of visible light, opposite contrasts at local adjacent regions on the surface of the 2D colloidal crystals have been observed. The understanding of self-assembly of the microspheres during the LB process paves the way to fabricate the high-quality 2D colloidal crystals for various applications such as photonic papers and inks, stealth materials, biomimetic coatings, and related nanostructures.
- Published
- 2020
25. Toward a Reliable Synaptic Simulation Using Al-Doped HfO
- Author
-
Sourav, Roy, Gang, Niu, Qiang, Wang, Yankun, Wang, Yijun, Zhang, Heping, Wu, Shijie, Zhai, Peng, Shi, Sannian, Song, Zhitang, Song, Zuo-Guang, Ye, Christian, Wenger, Thomas, Schroeder, Ya-Hong, Xie, Xiangjian, Meng, Wenbo, Luo, and Wei, Ren
- Abstract
The potential in a synaptic simulation for neuromorphic computation has revived the research interest of resistive random access memory (RRAM). However, novel applications require reliable multilevel resistive switching (RS), which still represents a challenge. We demonstrate in this work the achievement of reliable HfO
- Published
- 2020
26. Reliable resistive switching of epitaxial single crystalline cubic Y-HfO
- Author
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Yankun, Wang, Gang, Niu, Qiang, Wang, Sourav, Roy, Liyan, Dai, Heping, Wu, Yanxiao, Sun, Sannian, Song, Zhitang, Song, Ya-Hong, Xie, Zuo-Guang, Ye, Xiangjian, Meng, and Wei, Ren
- Abstract
Previous studies have mainly focused on the resistive switching (RS) of amorphous or polycrystalline HfO
- Published
- 2020
27. Label-free distinction between p53+/+ and p53 -/- colon cancer cells using a graphene based SERS platform
- Author
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Gang Niu, Ming Xia, Huinan Liu, Pu Wang, Ya-Hong Xie, Fan Yang, Catherine Augello, and Owen Liang
- Subjects
Colorectal cancer ,Simulated body fluid ,Cell ,Biomedical Engineering ,Biophysics ,Metal Nanoparticles ,Biosensing Techniques ,02 engineering and technology ,Spectrum Analysis, Raman ,010402 general chemistry ,01 natural sciences ,law.invention ,symbols.namesake ,law ,Electrochemistry ,medicine ,Humans ,Gene knockout ,Label free ,Graphene ,Chemistry ,General Medicine ,021001 nanoscience & nanotechnology ,medicine.disease ,0104 chemical sciences ,medicine.anatomical_structure ,Cell culture ,Colonic Neoplasms ,symbols ,Graphite ,Tumor Suppressor Protein p53 ,0210 nano-technology ,Raman scattering ,Biotechnology - Abstract
Surface-Enhanced Raman Scattering (SERS) is used to differentiate two colon cancer cell line HCT 116, that is, to distinguish a TP53 gene knockout cell line (p53 -/-) from a wild type (p53 +/+). A label-free graphene/gold nanopyramid based SERS platform, combined with the multivariate analysis: principal component analysis, is used to profile live, dead, and burst colon cancer cells suspended in simulated body fluid (SBF). The graphene sheet permits SERS hotspot identification and provides a chemical enhancement for the biological constituents. This study found that a unique fingerprint exists for three different states of the cell, burst, live, and dead, which were used to differentiate the p53 +/+ and p53 -/- cell lines. Perceptron with Pocket Algorithm was also coupled with PCA to demonstrate an average of 81% sensitivity and 97% specificity in separating the two cell lines. The demonstration of single gene differentiation shows the great applicable potential of this SERS graphene hybrid platform for cancer diagnosis.
- Published
- 2018
28. Structure and band gap tunable CuInS2 nanocrystal synthesized by hot-injection method with altering the dose of oleylamine
- Author
-
Zirui Liu, Liwang Liu, Hong Li, and Ya-Hong Xie
- Subjects
Materials science ,Band gap ,business.industry ,Mechanical Engineering ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,chemistry ,Nanocrystal ,Mechanics of Materials ,Transmission electron microscopy ,Oleylamine ,Quantum dot ,Phase (matter) ,lcsh:TA401-492 ,Optoelectronics ,lcsh:Materials of engineering and construction. Mechanics of materials ,General Materials Science ,0210 nano-technology ,business ,Wurtzite crystal structure - Abstract
By hot-injection method with altering the dose of oleylamine (OAm) in a reaction system, CuInS2 (CIS) nanocrystal with tunable structure and band gap is synthesized. Through various measurements, including X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), it is demonstrated experimentally that when the dose of OAm is relatively high (2.0 and 2.5 ml in this work), the combination phase of pseudo-chalcopyrite/wurtzite are obtained with a surprising existence of nanotwins. Besides, the molar fraction of wurtzite is larger in the sample using 2.5 ml OAm in the reaction system. However, when the dose of OAm becomes low, (0, 1.0 and 1.5 ml), pure zinc-blende CIS pyramidal quantum dots (QDs) can be prepared. This indicates that oleylamine promotes the formation of wurtzite structure. In addition, the band gap is larger with increasing of OAm, following the quantum refinement effects. This work serves as a facile method of synthesizing CIS nanocrystal with tunable structure and band gap, which will be possibly applied in the fabrication of their optoelectronic devices. Keywords: CuInS2 nanocrystal, Tunable, Structure, Band gap, Optical properties
- Published
- 2018
29. High-quality GaN epitaxially grown on Si substrate with serpentine channels
- Author
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Xiaodong Hu, Jun Tang, Ya-Hong Xie, Hui Liao, Hua Zong, Shengxiang Jiang, Yue Yang, Wenjie Wang, Li Junze, and Tiantian Wei
- Subjects
010302 applied physics ,Fabrication ,Materials science ,business.industry ,Transistor ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Laser ,Epitaxy ,01 natural sciences ,law.invention ,Quality (physics) ,law ,0103 physical sciences ,Optoelectronics ,General Materials Science ,Electrical and Electronic Engineering ,Dislocation ,0210 nano-technology ,business ,Light-emitting diode ,Diode - Abstract
A novel serpentine-channeled mask was introduced to Si substrate for low-dislocation GaN epitaxial growth and the fully coalesced GaN film on the masked Si substrate was achieved for the first time. Compared with the epitaxial lateral overgrowth (ELOG) growth method, this innovative mask only requires one-step epitaxial growth of GaN which has only one high-dislocation region per mask opening. This new growth method can effectively reduce dislocation density, thus improving the quality of GaN significantly. High-quality GaN with low dislocation density ∼2.4 × 107 cm−2 was obtained, which accounted for about eighty percent of the GaN film in area. This innovative technique is promising for the growth of high-quality GaN templates and the subsequent fabrication of high-performance GaN-based devices like transistors, laser diodes (LDs), and light-emitting diodes (LEDs) on Si substrate.
- Published
- 2018
30. Synthesis of the 0D/3D CuO/ZnO Heterojunction with Enhanced Photocatalytic Activity
- Author
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Pengfei Xia, Linyu Zhu, Zirui Liu, Ya-Hong Xie, Dehua Xiong, and Hong Li
- Subjects
Materials science ,Composite number ,Heterojunction ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,General Energy ,Chemical engineering ,chemistry ,Photocatalysis ,Phenol ,Physical and Theoretical Chemistry ,0210 nano-technology ,Electronic band structure ,Photodegradation ,Wet chemistry ,Deposition (law) - Abstract
Construction of heterojunctions has aroused great interest recently in the photocatalysis field because of the special electronic band structure and unique physicochemical properties. In this work, a novel 0D/3D CuO/ZnO heterojunction was obtained via in situ deposition of CuO nanoparticles on the flowerlike ZnO surface using the wet chemistry method. After depositing CuO nanoparticles onto the ZnO, the CuO/ZnO heterojunction exhibits enhanced visible-light harvesting and effective separation of the photogenerated electron–hole pairs compared with those in the pure ZnO. The photocatalytic removal efficiency of phenol over the CuO/ZnO heterojunction is up to 78% under the irradiation of the light, which is ∼2 and ∼4 times higher than those of the pristine ZnO and CuO, respectively. This composite also presents good durability and stability for phenol degradation in the photocatalytic reactions. Additionally, in the photodegradation system of the CuO/ZnO heterojunction, the superoxide radicals (•O2–) and hy...
- Published
- 2018
31. Synthesis of hierarchical ZnO&Graphene composites with enhanced photocatalytic activity
- Author
-
Linyu Zhu, Hong Li, Zirui Liu, Pengfei Xia, and Ya-Hong Xie
- Subjects
Materials science ,Graphene ,Process Chemistry and Technology ,Radical ,Composite number ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Specific surface area ,Materials Chemistry ,Ceramics and Composites ,Photocatalysis ,Rhodamine B ,Degradation (geology) ,Composite material ,0210 nano-technology ,Visible spectrum - Abstract
A novel quasi core-shell structure of hierarchical ZnO coated with graphene, has been synthesized by a simple solvothermal method. After loading graphene on the surface of hierarchical ZnO, an intimate interfacial contact between them has been achieved. The experimental results indicate that hierarchical ZnO&Graphene composites (HZ&G) have large specific surface area, enhanced light harvesting in the visible light region, better separation efficiency and fast transfer rate of photo-generated carriers. Therefore, the HZ&G composites exhibit superior photocatalytic degradation efficiency over Rhodamine B (RhB) compared to pure hierarchical ZnO. Especially for HZ&G 15 composite with the nominal weight concentration of 15% GO, its removal rate of simulated pollutants is up to 98.5% under current experimental conditions. The primary reactive species in the process of photocatalytic RhB degradation is also confirmed by trapping experiments to be hydroxyl radicals (•OH). Meanwhile, a probable mechanism of enhancement over photocatalytic RhB degradation has been proposed.
- Published
- 2018
32. Solvothermal synthesis, electromagnetic and electrochemical properties of jellylike cylinder graphene-Mn 3 O 4 composite with highly coupled effect
- Author
-
Hong Li, Ya-Hong Xie, Xie Junliang, Zirui Liu, and Yuting Long
- Subjects
Materials science ,Graphene ,Solvothermal synthesis ,Composite number ,Reflection loss ,Nanoparticle ,02 engineering and technology ,Conductivity ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Capacitance ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,law.invention ,Inorganic Chemistry ,law ,Materials Chemistry ,Ceramics and Composites ,Physical and Theoretical Chemistry ,Composite material ,0210 nano-technology ,Microwave - Abstract
Jellylike cylinder graphene-Mn3O4 composite with highly coupled effect was successfully synthesized by a simple solvothermal process. Without using toxic reducing agent and expensive equipment, this method is environmental compatible and suitable for low cost mass production. High capacitance Mn3O4 nanoparticles are homogeneously anchored on excellent conductivity graphene framework and a growth mechanism is hypothesized. Excellent electron conductivity and unique structure of Mn3O4-graphene composite give rise to various applications such as microwave absorber and electrode material. As a microwave absorber, the composite exhibits lowest reflection loss of −14.2 dB in the frequency range of 2–18 GHz. Good microwave absorption performance is due to the structure of the composite where conductive channels form between nano sized Mn3O4 and high conductivity graphene with defects and dangling bonds. As for electrochemical property, Mn3O4-graphene composite with coupled effect shows excellent performance with highest specific capacitance of 246.7 F g−1 in saturated K2SO4 at a scan rate of 5 mV s−1. Good electrochemical property is also attributed to the structure with high utilization of Mn3O4, fast charge carrier transmission, and excellent electronic conductivity. This composite shows a promising application in absorbing materials and electrodes.
- Published
- 2017
33. Systematic transient characterisation of graphene NEMS switch for ESD protection
- Author
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Qi Chen, Feilong Zhang, Cheng Li, Ya-Hong Xie, Chenkun Wang, Jimmy Ng, Albert Wang, and Fei Lu
- Subjects
010302 applied physics ,Nanoelectromechanical systems ,Electrostatic discharge ,Materials science ,business.industry ,Graphene ,020208 electrical & electronic engineering ,Biomedical Engineering ,Bioengineering ,02 engineering and technology ,Integrated circuit ,Condensed Matter Physics ,01 natural sciences ,Human-body model ,law.invention ,Electric power transmission ,law ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Optoelectronics ,General Materials Science ,Transient (oscillation) ,business ,Transmission-line pulse - Abstract
Integrated circuits (ICs) require robust and low-parasitic on-chip electrostatic discharging (ESD) protection. Compared to conventional in-Si PN-junction-based ESD protection structures, a novel above-IC graphene nanoelectromechanical system (NEMS) switch (gNEMS) ESD protection structure features low parasitic effects and superior current and heat handling capability. This work reports a systematic transient characterisation of gNEMS ESD switches by transmission line pulse (TLP) measurement for human body model ESD protection, revealing transient ESD discharging behaviours related to device dimensions and TLP pulse shapes. It provides practical design guidelines for using gNEMS switch as on-chip ESD protection for ICs. Unlike in-Si ESD protection structures, the new gNEMS ESD switch devices can be made in the back-end-of-line of ICs through three-dimensional heterogeneous integration.
- Published
- 2017
34. Comparative study between the fracture stress of poly‐ and single‐crystalline graphene using a novel nanoelectromechanical system structure
- Author
-
Ya-Hong Xie, Albert Wang, Qi Chen, Jimmy Ng, and Tianru Wu
- Subjects
010302 applied physics ,Nanoelectromechanical systems ,Materials science ,Graphene ,Biomedical Engineering ,Bioengineering ,Nanotechnology ,02 engineering and technology ,Chemical vapor deposition ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,law.invention ,Stress (mechanics) ,law ,0103 physical sciences ,Monolayer ,Fracture (geology) ,General Materials Science ,Grain boundary ,Crystallite ,Composite material ,0210 nano-technology - Abstract
Graphene is a two-dimensional carbon material with extraordinary mechanical properties. However, recent studies have found that the presence of grain boundaries significantly decreases fracture stress of graphene, warranting further investigation. This work reports the development of a new method to measure the fracture stress of monolayer graphene with a novel nanoelectromechanical system (NEMS) structure. Suspended graphene ribbon devices with a range of geometries were electrostatically actuated while the graphene sheet was pinned down with various nail structures. By recording the electromechanical responses at fracture and using finite element simulations, the fracture stress was calculated. Using this novel NEMS structure, the fracture stress of polycrystalline graphene grown using conventional chemical vapour deposition (CVD) and single-crystalline graphene grown using local feeding CVD were found to be ∼30 and ∼90 GPa, respectively.
- Published
- 2017
35. Non-polar true-lateral GaN power diodes on foreign substrates
- Author
-
Guo Yu, Jia Wang, Wentao Cai, Xiaodong Hu, Hua Zong, Ya-Hong Xie, Yaqiang Liao, Hiroshi Amano, and Weifang Lu
- Subjects
010302 applied physics ,Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Schottky diode ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,Cathode ,Anode ,law.invention ,Power (physics) ,law ,Electric field ,0103 physical sciences ,Sapphire ,Optoelectronics ,0210 nano-technology ,business ,Diode - Abstract
We have demonstrated non-polar GaN power diodes (Schottky barrier diode and p–n junction diode) on foreign substrates featuring the true-lateral p–n and metal–semiconductor junctions. The diodes were fabricated on GaN islands laterally overgrown on the mask-patterned sapphire and Si substrates by metalorganic vapor phase epitaxy. The anode and cathode were formed on the opposed a-plane sidewalls of the island, making the device architecture essentially like the 90° rotation of the desired true-vertical power diodes. The ideality factor of the Schottky barrier diode remained 1.0 (from 1.00 to 1.05) over 7 decades in current. Specifically, a high critical electric field of 3.3 MV/cm was demonstrated on the p–n junction diode with avalanche capability. These performances reveal a strong potential of non-polar GaN with the true-lateral junctions for high power applications.
- Published
- 2021
36. Source identification and method for drastic reduction of Fe contamination on wet transferred graphene
- Author
-
Ya-Hong Xie and Jimmy Ng
- Subjects
Materials science ,Nanotechnology ,02 engineering and technology ,Chemical vapor deposition ,010402 general chemistry ,01 natural sciences ,law.invention ,symbols.namesake ,Optical microscope ,law ,Materials Chemistry ,FOIL method ,Graphene oxide paper ,Graphene ,Metals and Alloys ,Surfaces and Interfaces ,Contamination ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Chemical engineering ,symbols ,0210 nano-technology ,Raman spectroscopy ,Layer (electronics) - Abstract
Graphene is a 2D material with extraordinary electronic and mechanical properties and has a wide range of applications. Among existing synthesis methods, chemical vapor deposition (CVD) onto Cu foil is the most prominent because it allows large area high quality graphene to be prepared at relatively low costs and then subsequently wet transferred to arbitrary substrates. Typically, PMMA and FeCl 3 are used as a polymeric support layer and a metal etchant respectively during wet transfer. Unfortunately, this method leaves graphene susceptible to contamination, degrading transferred graphene's extraordinary properties. In this paper, contamination in the form of black particulates is identified to be Fe wrapped in graphene and a model of how it originates was developed. Then, a procedure to reduce this contamination during wet transfer was developed and its effectiveness was systematically studied. Transfers were characterized using Raman spectroscopy and optical microscopy with image segmentation. Experimental data obtained indicates that this simple and economic method is very effective in reducing Fe contamination on transferred CVD graphene, offering a way to improve the wet transfer process.
- Published
- 2017
37. Growth and characterization of graphite doped CdTe/CdS thin film heterojunction
- Author
-
Ya-Hong Xie, M. Asif Nawaz, Hammad M. Arbi, Mughees Shahid, Muhammad Asghar, Faisal Iqbal, and Waqas Khalid
- Subjects
Materials science ,business.industry ,Doping ,Heterojunction ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Cadmium telluride photovoltaics ,0104 chemical sciences ,Characterization (materials science) ,Optoelectronics ,General Materials Science ,Graphite ,Thin film ,0210 nano-technology ,business - Published
- 2017
38. Vertical PN Junction-based GaN Power Diode
- Author
-
Yoshio Honda, S. Jiang, T. Liu, H. Zong, Hiroshi Amano, X. Hu, Yuto Ando, J. Shen, Y. Liao, Ya-Hong Xie, and Jia Wang
- Subjects
Materials science ,business.industry ,Power diode ,Optoelectronics ,business ,p–n junction - Published
- 2019
39. Molecular orientation and specificity in the identification of biomolecules via surface enhanced Raman spectroscopy
- Author
-
Li Wei, Owen Liang, Ya-Hong Xie, Xinke Yu, and Yu Bai
- Subjects
chemistry.chemical_classification ,Orientation (computer vision) ,Protein Conformation ,Biomolecule ,Biophysics ,Proteins ,Cell Biology ,Surface-enhanced Raman spectroscopy ,Spectrum Analysis, Raman ,Biochemistry ,Amino acid ,symbols.namesake ,chemistry ,symbols ,Molecule ,Humans ,Amino Acid Sequence ,Raman spectroscopy ,Molecular Biology ,Protein secondary structure ,Protein size - Abstract
The orientation dependence of the Raman spectral features of individual protein/biomolecules is studied using surface-enhanced Raman spectroscopy (SERS). Large variation in spectral features mainly in term of peak intensity is observed from small proteins/peptides. We aim to address the question of whether the spectral features of SERS are uniquely determined by the type of protein/molecules or are influenced prominently by factors more than the identity of the molecules such as orientation of molecules relative to the substrate surface. The standard deviation in the intensity of individual Raman peaks diminishes for protein size larger than 13 amino acids. Secondary structure of protein (such as protein-protein interaction) remains unchanged regardless of protein orientation. Numerical simulation studies corroborate the experimental observation in that the SERS spectral features of biomedically relevant protein (of larger than 13 amino acids in size, which represent all human protein types) are not affected by the orientation of amino acids randomly dispersed on SERS-active surfaces. These findings are instrumental to understanding the exceedingly high (label-free) specificity when SERS is used in identifying proteins/peptides as can be found in numerous publications from different research groups in both in vivo and in vitro analyses. It was noted that the spectral position of all Raman peaks assignable to the various amino acids are independent of molecule orientation even though their intensities do vary.
- Published
- 2019
40. Graphene-Based on-Chip ESD Protection
- Author
-
Ya-Hong Xie, Mengfu Di, Cheng Li, Albert Wang, Jimmy Ng, Han Wang, Chenkun Wang, Feilong Zhang, and Qi Chen
- Subjects
Nanoelectromechanical systems ,Reliability (semiconductor) ,Electrostatic discharge ,Materials science ,business.industry ,Graphene ,law ,Optoelectronics ,System on a chip ,Transient (oscillation) ,Transient analysis ,business ,law.invention - Abstract
Electrostatic discharge (ESD) failure is a devastating IC reliability problem. Traditional in-Si PN-junction based on-chip ESD protection structures are becoming unsuitable to IC at advanced technology nodes due to ESD-induced parasitic effects and layout issues [1–3]. On-chip ESD protection for future chips calls for revolutionary solutions. This paper reviews recent advances in developing graphene-based ESD protection structures including systematic and statistical transient ESD characterization of graphene ribbons (GR) as possible ESD interconnects [4] and graphene nano-electromechanical system (NEMS) ESD protection structures [3, 5]. The novel graphene-based ESD protection concept shows the potential for future chips.
- Published
- 2019
41. The conversion of CuInS
- Author
-
Liwang, Liu, Hong, Li, Zirui, Liu, and Ya-Hong, Xie
- Abstract
Colloidal quantum dots (QDs) have attracted a great amount of attention for their appealing optoelectronic properties. In this work, the CuInS
- Published
- 2019
42. A Label-Free Platform for Identification of Exosomes from Different Sources
- Author
-
Suman Dutta, Xinke Yu, Feng Ji, Neda Mesgarzadeh, Zirui Liu, Gal Bitan, Ya-Hong Xie, and Zhongbo Yan
- Subjects
principal component analysis ,Biomedical Engineering ,Bioengineering ,02 engineering and technology ,Computational biology ,Raman mapping ,Exosomes ,Spectrum Analysis, Raman ,01 natural sciences ,Exosome ,Analytical Chemistry ,High spatial resolution ,exosome ,Nanotechnology ,Animals ,Raman ,Instrumentation ,Label free ,Fluid Flow and Transfer Processes ,chemistry.chemical_classification ,Spectrum Analysis ,Process Chemistry and Technology ,Biomolecule ,graphene ,010401 analytical chemistry ,Surface-enhanced Raman spectroscopy ,021001 nanoscience & nanotechnology ,surface-enhanced Raman spectroscopy ,Microvesicles ,4.1 Discovery and preclinical testing of markers and technologies ,0104 chemical sciences ,chemistry ,Multivariate Analysis ,biomarker ,Identification (biology) ,0210 nano-technology ,Ultracentrifugation - Abstract
Exosomes contain cell- and cell-state-specific cargos of proteins, lipids, and nucleic acids and play significant roles in cell signaling and cell-cell communication. Current research into exosome-based biomarkers has relied largely on analyzing candidate biomarkers, i.e., specific proteins or nucleic acids. However, this approach may miss important biomarkers that are yet to be identified. Alternative approaches are to analyze the entire exosome system, either by "omics" methods or by techniques that provide "fingerprints" of the system without identifying each individual biomolecule component. Here, we describe a platform of the latter type, which is based on surface-enhanced Raman spectroscopy (SERS) in combination with multivariate analysis, and demonstrate the utility of this platform for analyzing exosomes derived from different biological sources. First, we examined whether this analysis could use exosomes isolated from fetal bovine serum using a simple, commercially available isolation kit or necessitates the higher purity achieved by the "gold standard" ultracentrifugation/filtration procedure. Our data demonstrate that the latter method is required for this type of analysis. Having established this requirement, we rigorously analyzed the Raman spectral signature of individual exosomes using a unique, hybrid SERS substrate made of a graphene-covered Au surface containing a quasi-periodic array of pyramids. To examine the source of the Raman signal, we used Raman mapping of low and high spatial resolution combined with morphological identification of exosomes by scanning electron microscopy. Both approaches suggested that the spectra were collected from single exosomes. Finally, we demonstrate for the first time that our platform can distinguish among exosomes from different biological sources based on their Raman signature, a promising approach for developing exosome-based fingerprinting. Our study serves as a solid technological foundation for future exploration of the roles of exosomes in various biological processes and their use as biomarkers for disease diagnosis and treatment monitoring.
- Published
- 2019
43. Phase Change Random Access Memory for Neuro‐Inspired Computing
- Author
-
Ya-Hong Xie, Qiang Wang, Xi Li, Zhitang Song, Xiaogang Chen, Gang Niu, Wei Ren, Ruobing Wang, Zuo-Guang Ye, and Sannian Song
- Subjects
010302 applied physics ,Phase change ,Random access memory ,Theoretical computer science ,Materials science ,0103 physical sciences ,02 engineering and technology ,021001 nanoscience & nanotechnology ,0210 nano-technology ,01 natural sciences ,Electronic, Optical and Magnetic Materials - Published
- 2021
44. Copper Ion Binding Site in β-Amyloid Peptide
- Author
-
Diana Yugay, Jérôme Gilles, Lisa M. Kawakami, Dominic P. Goronzy, Paul S. Weiss, Yang Yang, Ya-Hong Xie, Zhongbo Yan, Shelley A. Claridge, and Tze-Bin Song
- Subjects
0301 basic medicine ,Secondary ,Aging ,Circular dichroism ,Beta sheet ,Peptide ,Plasma protein binding ,Neurodegenerative ,Alzheimer's Disease ,01 natural sciences ,Protein Structure, Secondary ,2.1 Biological and endogenous factors ,Alzheimer's Disease including Alzheimer's Disease Related Dementias ,General Materials Science ,Aetiology ,chemistry.chemical_classification ,β-amyloid ,Condensed Matter Physics ,Amino acid ,Copper ion binding ,Neurological ,scanning tunneling microscopy ,Alzheimer’s disease ,Protein Binding ,Protein Structure ,Bioengineering ,010402 general chemistry ,03 medical and health sciences ,Alzheimer Disease ,Acquired Cognitive Impairment ,Humans ,Histidine ,Nanoscience & Nanotechnology ,Binding site ,Amyloid beta-Peptides ,Binding Sites ,binding site ,Mechanical Engineering ,Neurosciences ,Alzheimer's Disease including Alzheimer's Disease Related Dementias (AD/ADRD) ,General Chemistry ,histidine brace ,Peptide Fragments ,Brain Disorders ,0104 chemical sciences ,Crystallography ,030104 developmental biology ,β-sheet ,chemistry ,Biophysics ,Dementia ,Copper - Abstract
β-Amyloid aggregates in the brain play critical roles in Alzheimer's disease, a chronic neurodegenerative condition. Amyloid-associated metal ions, particularly zinc and copper ions, have been implicated in disease pathogenesis. Despite the importance of such ions, the binding sites on the β-amyloid peptide remain poorly understood. In this study, we use scanning tunneling microscopy, circular dichroism, and surface-enhanced Raman spectroscopy to probe the interactions between Cu2+ ions and a key β-amyloid peptide fragment, consisting of the first 16 amino acids, and define the copper-peptide binding site. We observe that in the presence of Cu2+, this peptide fragment forms β-sheets, not seen without the metal ion. By imaging with scanning tunneling microscopy, we are able to identify the binding site, which involves two histidine residues, His13 and His14. We conclude that the binding of copper to these residues creates an interstrand histidine brace, which enables the formation of β-sheets.
- Published
- 2016
45. SERS optical fiber probe with plasmonic end‐facet
- Author
-
Ya-Hong Xie, Ming Xia, Pei Zhang, and Claris Leung
- Subjects
optical fiber ,Materials science ,Optical fiber ,Bioengineering ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,law.invention ,symbols.namesake ,law ,General Materials Science ,Surface plasmon resonance ,Spectroscopy ,Plasmon ,Chemical Physics ,SERS ,Graphene ,Mechanical Engineering ,graphene ,Condensed Matter Physics ,021001 nanoscience & nanotechnology ,Laser ,0104 chemical sciences ,Numerical aperture ,symbols ,Raman microscope ,0210 nano-technology ,Raman spectroscopy ,Physical Chemistry (incl. Structural) - Abstract
Research article Received: 20 April 2016 Revised: 18 August 2016 Accepted: 20 August 2016 Published online in Wiley Online Library: 14 September 2016 (wileyonlinelibrary.com) DOI 10.1002/jrs.5031 SERS optical fiber probe with plasmonic end- facet Ming Xia, a * Pei Zhang, a Claris Leung a and Ya-Hong Xie a,b Surface-enhanced Raman spectroscopy (SERS) is a surface-sensitive technique that can enhance the intensity of Raman signal by several orders of magnitude, enabling even the detection of single molecule. This work presents the experimental and theoretical studies of an optical fiber probe with nano-structured end-facet for bio-sensing applications via SERS. The factors affecting the intensity of Raman signal passing through the fiber probe are investigated. These factors include the numerical aperture of the objective lens, the slit width of the spectrometer, the fiber length, and the size of SERS nano-array. The Raman signal loss through fiber compared with optical microscope-based free-space Raman detection is estimated. To further enhance the SERS enhance- ment factor, a hybrid graphene/Au nano-triangle structure is transferred on the end-facet of the fiber probe to enable SERS. Superimposing graphene layer on Au nano-structure is found to be superior over bare Au nano-structure in terms of the detection sensitivity. Copyright © 2016 John Wiley & Sons, Ltd. Additional supporting information may be found in the online version of this article at the publisher’s web site. Keywords: SERS; optical fiber; graphene Introduction J. Raman Spectrosc. 2017, 48, 211–216 Methods The SERS fiber probe is prepared by transferring Au nano-triangle array onto the fiber facet. The fabrication process is shown in Fig. S1. SERS measurement is conducted using Renishaw inVia confocal Raman microscope with 785 nm laser (12.5 mW power with 20 s * Correspondence to: Ming Xia, Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA. E-mail: xiaming@g.ucla.edu a Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, 90095, USA b Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, CA, 90095, USA Copyright © 2016 John Wiley & Sons, Ltd. Surface-enhanced Raman spectroscopy (SERS) is an important ana- lytical technique that is able to provide single molecule detection and high-resolution spectral information. [1] It is capable of single molecule detection and allows for label-free detection with high degree of specificity. [2] Molecules absorbed at the metallic surface experience a large amplification of the electromagnetic field because of local surface plasmon resonance leading to orders of magnitude increase in Raman yield and greatly enhanced Raman signal. To achieve high SERS enhancement factors (EFs), many ef- forts have been devoted to develop various metallic (mainly Au and Ag) nano-structures to enhance the local electromagnetic field. [3–5] In addition to the traditional metallic nano-structures, graphene and other two-dimensional materials have also been ex- plored to enhance the Raman signal. [6–9] SERS has been explored for in vivo tumor detection with labeled Au nanoparticles, [10,11] in which the specificity of detection is enabled by labeling technique. Compared with labeled nanoparticles, SERS optical fiber probe with single-ended measurement geometry [12–19] has been gaining at- tention for in vivo label-free bio-sensing because of their flexibility and compatibility with remote sensing. A label-free detection scheme allows real-time detection and eliminates the time and cost-consuming labeling procedures. [20] Moreover, label-free SERS renders vibrational information akin to fingerprints of the bio- molecules that is in principle more specific than any labeling approaches. The most common method to couple SERS substrates with optical fiber is to modify the fiber end with SERS substrates such as Ag or Au nanoparticles. [14–16,21] Nanoparticle-coated optical fiber probe for in vitro SERS measurement [14,16] can achieve EF on the order of 10 4 –10 5 , lower than the common single molecule SERS EF of ~10 7 –10 8 . [2] SERS fiber probes prepared using this method have spatial resolution similar to the fiber core diameter (usually larger than 10 μm). However, higher spatial resolution is demanded in certain bio-sensing, like in vivo neurochemical monitoring. [22] For instance, measurement of neurodynamics within individual synap- tic clefts (tens of nanometers [23] ) represents the most extreme chal- lenge. To expand the SERS fiber probe for in vivo bio-sensing, optimization of SERS fiber probe is required to provide higher SERS EF and spatial resolution. The optimization of SERS fiber probe can be achieved only if the key factors affecting the sensitivity are well understood. This paper describes our effort in gaining such understanding. We prepare SERS fiber probes based on Au nano-triangle array and propose a method to enhance its spatial resolution. The key factors studied here include the numerical aperture (NA) of objective lens, the slit width of spectrometer, the fiber length, and the size of SERS nano-array. The Raman signal loss through the fiber is estimated compared with normal Raman detection. To further enhance the SERS EF, a hybrid graphene/Au nano-triangle structure is trans- ferred on fiber facet. SERS fiber probe with hybrid graphene/Au nano-triangle structure is found to have better performance than the fiber probe with bare Au nano-triangle structure.
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- 2016
46. Luminescence Properties of Sm3+/Eu3+ Co-Doped ZnO Quantum Dots
- Author
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Zuhu Ye, Fengyi Liu, Mingyue Li, Yun Mou, Kun Yang, Ya-Hong Xie, Hong Li, Yajing Hu, and Jin Na
- Subjects
Materials science ,Photoluminescence ,business.industry ,Doping ,Biomedical Engineering ,Analytical chemistry ,Bioengineering ,Nanotechnology ,General Chemistry ,Condensed Matter Physics ,Semiconductor ,Quantum dot ,Transmission electron microscopy ,General Materials Science ,High-resolution transmission electron microscopy ,business ,Luminescence ,Wurtzite crystal structure - Abstract
In order to improve luminescence properties of semiconductor ZnO quantum dots (QDs), Sm3+/Eu3+ co-doped ZnO QDs have been controllably synthesized by sol–gel method in this paper. ZnO QDs have a spherical shape with mean diameter at about 5–6 nm, which was characterized by high-resolution transmission electron microscopy (HRTEM). ZnO QDs have hexagonal wurtzite structure with parts of Sm3+ and Eu3+ incorporated into the lattice, which was demonstrated by X-ray Diffraction (XRD). Luminescence properties at room temperature (RT) of different amount of Sm3+ and 2 mol% Eu3+ doped ZnO QDs were examined in-depth by optical spectra. In contrast to the Pr3+/Eu3+ co-doped fluorescent performance researched in our previous study, the photoluminescence (PL) spectra indicates the unique luminescence properties of Sm3+/Eu3+ co-doped ZnO QDs. In addition, fluorescence lifetimes were obtained to illustrate the luminous mechanism.
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- 2016
47. Reliable resistive switching of epitaxial single crystalline cubic Y-HfO2 RRAMs with Si as bottom electrodes
- Author
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Sannian Song, Ya-Hong Xie, Yankun Wang, Wei Ren, Sourav Roy, Wu Heping, Xiangjian Meng, Qiang Wang, Yanxiao Sun, Liyan Dai, Zuo-Guang Ye, Zhitang Song, and Gang Niu
- Subjects
Materials science ,Photoemission spectroscopy ,Bioengineering ,02 engineering and technology ,010402 general chemistry ,Epitaxy ,01 natural sciences ,symbols.namesake ,General Materials Science ,Electrical and Electronic Engineering ,Thin film ,business.industry ,Mechanical Engineering ,Doping ,Heterojunction ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Amorphous solid ,Mechanics of Materials ,Transmission electron microscopy ,symbols ,Optoelectronics ,0210 nano-technology ,business ,Raman spectroscopy - Abstract
Previous studies have mainly focused on the resistive switching (RS) of amorphous or polycrystalline HfO2-RRAM. The RS of single crystalline HfO2 films has been rarely reported. Yttrium doped HfO2 (YDH) thin films were fabricated and successful Y incorporation into HfO2 was confirmed by x-ray photoemission spectroscopy. A pure cubic phase of YDH and an abrupt YDH/Si interface were obtained and verified by x-ray diffraction, Raman spectroscopy and transmission electron microscopy. A Pt/YDH/n++-Si heterostructure using Si as the bottom electrode was fabricated, which shows stable RS with an ON/OFF ratio of 100 and a reliable data retention (104 s). The electron transport mechanism was investigated in detail. It indicates that hopping conduction is dominating when the device is at a high resistance state, while space charge limited conduction acts as the dominant factor at a low resistance state. Such behavior, which is different from devices using TiN or Ti as electrodes, was attributed to the Y doping and specific YDH/Si interface. Our results demonstrate a proof of concept study to use highly doped Si as bottom electrodes along with single crystalline YDH as insulator layer for such RRAM applications as wireless sensors and synaptic simulation.
- Published
- 2020
48. Effects of polymer residue on the pull-in of suspended graphene
- Author
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Talmage Jones, Albert Wang, Jimmy Ng, Jonathan B. Hopkins, Ya-Hong Xie, and Isaac Martinez-Velis
- Subjects
Materials science ,02 engineering and technology ,Chemical vapor deposition ,01 natural sciences ,Strain energy ,law.invention ,law ,0103 physical sciences ,Ribbon ,Materials Chemistry ,Electrical and Electronic Engineering ,Composite material ,Instrumentation ,010302 applied physics ,Microelectromechanical systems ,chemistry.chemical_classification ,Graphene ,Process Chemistry and Technology ,Polymer ,Interaction energy ,021001 nanoscience & nanotechnology ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Photolithography ,0210 nano-technology - Abstract
Graphene is an ideal candidate for building microelectromechanical system (MEMS) devices because of its extraordinary electronic and mechanical properties. Some research has been done to study the MEMS pull-in phenomenon in suspended graphene, but no one has yet considered the effects of polymer residue. Polymer residue is an inevitable consequence when transferring polycrystalline graphene (PCG) grown using chemical vapor deposition, the most common graphene growth method. Polymer residue is also introduced when using photolithography to build MEMS devices. In this paper, the authors study the effects of polymer residue on the pull-in of suspended PCG ribbon devices and find that thick polymer residues cause a variation in pull-in voltage. However, after removing most of the polymer residue using a more abrasive chloroform treatment, the authors find that the graphene structure is no longer able to suspend itself as the graphene-substrate interaction energy becomes greater than the strain energy needed to conform graphene to the substrate. Therefore, polymer residue is found to cause variation in the pull-in voltage but is also found to help in graphene’s suspension at high length to displacement ratios.
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- 2020
49. Uniform growth of high-concentration MoS2 nanoflakes on plasma treated carbon nanotube sheet
- Author
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Wenbo Xin, Peiyi Ye, Ya-Hong Xie, and Li Zheng
- Subjects
High concentration ,Materials science ,Mechanical Engineering ,Substrate (chemistry) ,02 engineering and technology ,Carbon nanotube ,Chemical vapor deposition ,Plasma ,Active surface ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,law.invention ,symbols.namesake ,Chemical engineering ,Mechanics of Materials ,law ,symbols ,General Materials Science ,0210 nano-technology ,High-resolution transmission electron microscopy ,Raman spectroscopy - Abstract
In this report, we demonstrate a novel two-step approach that is capable of growing uniform high-concentration MoS2 nanoflakes on the carbon nanotube (CNT) sheet substrate. The CNT sheet is simply activated by the oxygen plasma to separate large CNT bundles and to create more active surface sites. A typical chemical vapor deposition (CVD) process is employed, enabling the direct growth of MoS2 nanoflakes on the activated CNT substrate. Morphologies and structures of MoS2/CNT nanohybrid are characterized by SEM/EDS, high-resolution TEM (HRTEM) and Raman spectroscopy. Our results suggest that the plasma treatment of CNT sheet is critical to obtain well-dispersed large quantity of MoS2 nanoflakes on CNT assemblies.
- Published
- 2019
50. Design of a Graphene Nanoribbon Electrostatic Discharge Compliant Mechanism
- Author
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Jonathan B. Hopkins, Talmage Jones, Ya-Hong Xie, and Jimmy Ng
- Subjects
Materials science ,Electrostatic discharge ,business.industry ,Graphene ,law ,Compliant mechanism ,Optoelectronics ,business ,Capacitance ,law.invention - Abstract
This paper investigates the design of an electrostatic discharge protection device made of single-layer graphene nanoribbons. The device is meant to trigger electrostatic discharge at a target voltage of 1.5V. Other design requirements include the minimization of parasitic capacitance, electrical response time and mechanical response time. The device is designed to discharge static electricity by being pulled to ground through electrostatic forces, then making contact with ground before returning to its original position. Previous designs experienced repeatability issues due to a lack of securing the ribbon and mechanical failure due to high stresses at the boundary conditions. New designs are presented and optimized to maintain a high effective spring constant for the device while reducing stress during electrostatic pull-in. A single-degree of freedom model is used in conjunction with the Bernoulli-Euler beam equations and Castigliano’s method to guide the design process. Behavior of each design is validated, and repeatability is assessed using finite-element simulations. The new designs are to be fabricated using a low pressure chemical vapor deposition process.
- Published
- 2018
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