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Single-walled carbon nanotube-based field effect transistors (SWCNT-FETs) are ideal candidates for fabricating sensors and have been widely used for chemical sensing applications. SWCNT-FETs have low selectivity because of the environmentally sensitive electronic properties of SWCNTs, and SWCNT-FETs also show a high noise signal and poor sensitivity because of charge trapping from Si–OH hydration of the SiO2/Si substrate on the SWCNTs. Herein, poly (4-vinylpyridine) (P4VP) was used for noncovalent attachment to SWCNTs and selective binding to copper ions (Cu2+). Importantly, the introduction of a hafnium-oxide (HfO2) layer through atomic layer deposition (ALD) overcame the charge trapping by SiO2 hydration and remarkably decreased the interference signal. The sensitivity of the P4VP/SWCNT/HfO2-FET sensor for Cu2+ was 7.9 μA μM−1, which was approximately 100 times higher than that of the P4VP/SWCNT/SiO2-FET sensor, and its limit of detection (LOD) was as low as 33 pmol L−1. Thus, the P4VP/SWCNT/HfO2-FET sensor is a promising candidate for the development of Cu2+-selective sensors and can be designed for the large-scale manufacturing of custom-made sensors in the future.

Black phosphorus (BP) has a high charge-carrier mobility (∼1000 cm2 V−1 s−1), but the bare BP degrades rapidly in the presence of oxygen and water which limits the application of the BP. In this study, a simple, non-covalent passivation strategy is developed by modifying of the BP with hexamethylendiamine (HA). The functionalized BP exhibits good stability over 4 weeks. The organic phase interdigital electrode which is constructed by stable HA/BP and tyrosinase displays lowest noise signal (0.025 nA) and relatively low detection limit (10 nmol L−1) for bisphenol A. This work provides a new strategy for construction of novel biofuel cell, bioelectronics and biosensors.

Carbon-bridged organosilicate films deposited by using different precursors are studied by both experimentally and theoretically. It is shown that carbon-bridged OSG films have higher Young Modulus (E) than methyl-terminated films and E(phenylene) > E(ethylene) > E(methylene). However, the k-values of these films show the same tendency and this is one of the drawbacks of carbon terminated materials when they are considered as low-k candidates. It is shown that the films having a phenylene bridge can be destructed by UV light with wavelength > 200 nm while ethylene or an ethylene bridged samples are stable. Mechanism of UV initiated destruction of phenylene bridged materials is analyzed by using quantum chemical calculations. The presented results allow to conclude that the presence of long aliphatic and aromatic bridges makes OSG materials more sensitive to UV light.

The oxygen plasma surface treatment prior to ohmic metal deposition was developed to reduce the ohmic contact resistance (RC) for AlGaN/GaN high electron mobility transistors (HEMTs) on a high-resistive Si substrate. The oxygen plasma, which was produced by an inductively coupled plasma (ICP) etching system, has been optimized by varying the combination of radio frequency (RF) and ICP power. By using the transmission line method (TLM) measurement, an ohmic contact resistance of 0.34 Ω∙mm and a specific contact resistivity (ρC) of 3.29 × 10–6 Ω∙cm2 was obtained with the optimized oxygen plasma conditions (ICP power of 250 W, RF power of 75 W, 0.8 Pa, O2 flow of 30 cm3/min, 5 min), which was about 74% lower than that of the reference sample. Atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), and photoluminescence (PL) measurements revealed that a large nitrogen vacancy, which was induced near the surface by the oxygen plasma treatment, was the primary factor in the formation of low ohmic contact. Finally, this plasma treatment has been integrated into the HEMTs process, with a maximum drain saturation current of 0.77 A/mm obtained using gate bias at 2 V on AlGaN/GaN HEMTs. Oxygen plasma treatment is a simple and efficient approach, without the requirement of an additional mask or etch process, and shows promise to improve the Direct Current (DC)and RF performance for AlGaN/GaN HEMTs.

We demonstrate the controllable and preferentially oriented growth of electrochemically deposited Au films in non-toxic sulfite electrolyte. To investigate the initial deposition, sub-10-nm-resolution orientation mapping of the Au thin films used as cathode was performed. On this cathode, the nucleation density and growth rate of nuclei are simultaneously modulated by tuning the pulse current density, resulting in variations in morphology, grain size and crystal orientation. These distinct textures greatly affects the characteristics of deposited Au films including Young's modulus and hardness. Furthermore, the interpretation is made for describing the formation of different microstructures in three cases. At an appropriate current density, the appropriate density of nuclei and the subsequent growth lead to preferential growth at orientation and suppression of growth at other orientations. The results presented in this work would be beneficial to wide applications of Au electrochemical deposition in sulfite electrolyte. (c) The Author(s) 2018. Published by ECS.

The charge neutrality level of SiO2 is experimentally extracted by investigating conduction band offset (CBO) of SiO2/Si stack with different SiO2 thicknesses using X-ray photoelectron spectroscopy. The CBO is found to be dependent on SiO2 thickness. The CNL of SiO2 is determined to be 4 eV above valence band maximum by modeling the CBO vs. thickness of SiO2 using gap states and charge neutrality level based model.

Surface-enhanced Raman spectroscopy (SERS) substrates with high sensitivity and reproducibility are highly desirable for high precision and even molecular-level detection applications. Here, large-scale uniformly hybrid nanoparticle-enhanced Raman spectroscopy (NERS) substrates with high reproducibility and controllability were developed. Using oxygen plasma treatment, large-area and uniformly rough polystyrene sphere (URPS) arrays in conjunction with 20 nm Au films (AuURPS) were fabricated for SERS substrates. Au nanoparticles and clusters covered the surface of the URPS arrays, and this increased the Raman signal. In the detection of malachite green (MG), the fabricated NERS substrates have high reproducibility and sensitivity. The enhancement factor (EF) of Au nanoparticles and clusters was simulated by finite-difference time-domain (FDTD) simulations and the EF was more than 104. The measured EF of our developed substrate was more than 108 with a relative standard deviation as low as 6.64%&ndash, 13.84% over 15 points on the substrate. The minimum limit for the MG molecules reached 50 ng/mL. Moreover, the Raman signal had a good linear relationship with the logarithmic concentration of MG, as it ranged from 50 ng/mL to 5 &mu, g/mL. The NERS substrates proposed in this work may serve as a promising detection scheme in chemical and biological fields.

In this paper, the poly-Si nanowire (NW) field-effect transistor (FET) sensor arrays were fabricated by adopting low-temperature annealing (600 &deg, C/30 s) and feasible spacer image transfer (SIT) processes for future monolithic three-dimensional integrated circuits (3D-ICs) applications. Compared with other fabrication methods of poly-Si NW sensors, the SIT process exhibits the characteristics of highly uniform poly-Si NW arrays with well-controlled morphology (about 25 nm in width and 35 nm in length). Conventional metal silicide and implantation techniques were introduced to reduce the parasitic resistance of source and drain (SD) and improve the conductivity. Therefore, the obtained sensors exhibit &gt, 106 switching ratios and 965 mV/dec subthreshold swing (SS), which exhibits similar results compared with that of SOI Si NW sensors. However, the poly-Si NW FET sensors show the Vth shift as high as about 178 &plusmn, 1 mV/pH, which is five times larger than that of the SOI Si NW sensors. The fabricated poly-Si NW sensors with 600 &deg, C/30 s processing temperature and good device performance provide feasibility for future monolithic three-dimensional integrated circuit (3D-IC) applications.

Neoceratitis asiatica (Becker), which especially infests wolfberry (Lycium barbarum L.), could cause serious economic losses every year in China, especially to organic wolfberry production. In some important wolfberry plantings, it is difficult and time-consuming to rear the larvae or pupae to adults for morphological identification. Molecular identification based on DNA barcode is a solution to the problem. In this study, 15 samples were collected from Ningxia, China. Among them, five adults were identified according to their morphological characteristics. The utility of mitochondrial DNA (mtDNA) cytochrome c oxidase I (COI) gene sequence as DNA barcode in distinguishing N. asiatica was evaluated by analysing Kimura 2-parameter distances and phylogenetic trees. There were significant differences between intra-specific and inter-specific genetic distances according to the barcoding gap analysis. The uncertain larval and pupal samples were within the same cluster as N. asiatica adults and formed sister cluster to N. cyanescens. A combination of morphological and molecular methods enabled accurate identification of N. asiatica. This is the first study using DNA barcode to identify N. asiatica and the obtained DNA sequences will be added to the DNA barcode database.

Low-cost surface-enhanced Raman scattering (SERS) substrate with the largest possible enhancement factor is highly desirable for SERS-based sensing applications. In this work, we systematically investigated how the density of plasmonic nanostructures affects the intensity of SERS signal. By directly depositing of metallic layer on electron-beam-lithography defined dielectric nanoposts, plasmonic structures array with different densities were reliably fabricated for SERS measurements. Two main experimental phenomena were obtained: (1) the SERS intensity did not increase monotonically when increasing the density of plasmonic structures, and (2) these ultra-dense plasmonic structures resulted in the maximal SERS intensity. These results could be well explained based on finite-difference time domain (FDTD) simulations and provide robust experimental evidences to guide the design of the best possible SERS substrate.

Self-assembly has attracted increasing attention as an effective strategy for fabrication of functional micro/nanostructures in recent years. Capillary-force as a significant driving force of self-assembly has become a versatile and scalable approach to build complex geometries at the micro/nanoscales. In order to take full advantage of capillary-force to fabricate specific micro/nanoscales devices, we have done a thorough research on the mechanism of capillary-force self-assembly and analyzed the impact factors of micro/nanostructures suffered during the self-assembly process. In the aspect of application, we classified the main assembly methods, micro/nanostructures which can be got and their potential applications. Finally, we indicated that capillary-force self-assembly would have broad utilization in micro/nanofabrication due to its tunability and simplicity. Meanwhile, we put forward some issues that need to be solved in the further research.

CoTa alloy films as diffusion barriers for Cu/low-k interconnects are studied. Crystalline structure, thermal stability, barrier and sealing properties on low-k dielectric of CoTa alloys with different atomic ratios between Co and Ta are studied using different techniques. It is demonstrated that CoTa alloys with proper content and thickness can be considered as candidates to act as a barrier layer for Cu/low-k interconnects with acceptable thermal stability and resistivity. However, ultralow-k organosilicate based dielectrics with k = 2.25 and pore size about 2 nm can be sealed by this barrier against penetration of neutral molecules only when the CoTa alloy thickness is larger than 3 nm. Correlation of the barrier performance with low-k pore size is demonstrated.