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9 results on '"Wi, Sungjin"'

7. Nanoimprint-Assisted Shear Exfoliation (NASE) for Producing Multilayer MoS2Structures as Field-Effect Transistor Channel Arrays

Author

Chen, Mikai, Nam, Hongsuk, Rokni, Hossein, Wi, Sungjin, Yoon, Jeong Seop, Chen, Pengyu, Kurabayashi, Katsuo, Lu, Wei, and Liang, Xiaogan

Abstract

MoS2and other semiconducting transition metal dichalcogenides (TMDCs) are of great interest due to their excellent physical properties and versatile chemistry. Although many recent research efforts have been directed to explore attractive properties associated with MoS2monolayers, multilayer/few-layer MoS2structures are indeed demanded by many practical scale-up device applications, because multilayer structures can provide sizable electronic/photonic state densities for driving upscalable electrical/optical signals. Currently there is a lack of processes capable of producing ordered, pristine multilayer structures of MoS2(or other relevant TMDCs) with manufacturing-grade uniformity of thicknesses and electronic/photonic properties. In this article, we present a nanoimprint-based approach toward addressing this challenge. In this approach, termed as nanoimprint-assisted shear exfoliation (NASE), a prepatterned bulk MoS2stamp is pressed into a polymeric fixing layer, and the imprinted MoS2features are exfoliated along a shear direction. This shear exfoliation can significantly enhance the exfoliation efficiency and thickness uniformity of exfoliated flakes in comparison with previously reported exfoliation processes. Furthermore, we have preliminarily demonstrated the fabrication of multiple transistors and biosensors exhibiting excellent device-to-device performance consistency. Finally, we present a molecular dynamics modeling analysis of the scaling behavior of NASE. This work holds significant potential to leverage the superior properties of MoS2and other emerging TMDCs for practical scale-up device applications.

Published
2015
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8. Advanced Nanofabrication Technologies for Making Photo-Response Devices Based on Emerging Layered Transition Metal Dichalcogenides.

Author

Wi, Sungjin

Subjects
Photovoltaics, two dimensional materials, transition metal dichalcogenides, heterostructure, nanotechnology
Abstract

Emerging layered semiconductor materials, such as layered transition metal dichalcogenides (TMDCs), have exhibited attractive optoelectronic properties and hold a significant potential to be implemented for making new photoresponse devices. However, to realize working TMDC-based photoresponse devices for practical photovoltaic and photodetection applications, we need to (i) create new nanofabrication and nanomanufacturing technologies capable of producing TMDC devices with deterministic properties, architectures, and arrangements, (ii) develop new materials processing approaches capable of modulating various TMDCs to enable different device applications, and (iii) advance the device physics for understanding and leveraging the unique photonic properties of layered semiconductors. The research works presented in this thesis sought to advance the scientific/technical knowledge toward addressing the needs mentioned above and specifically focused on three relevant topics: (1) invention and demonstration of plasma-assisted transfer nanoprinting technology capable of producing orderly arranged layered material structures into device sites; (2) development and study of plasma-assisted doping processes, which can result in permanently stable doping effects in layered semiconductors; (3) characterization of a series of photoresponse devices based on emerging layered transition metal dichalcogenides (TMDCs), which were fabricated using various techniques, including plasma-assisted doping, stacking of graphene-TMDC heterostructures, and thin-film-metal-induced surface charge transfer (SCT) doping. The presented works have advanced the scientific knowledge and technical capability toward realizing working TMDC-based photoresponse devices for practical photovoltaic and photodetection applications. Additionally, the nanofabrication approaches developed in these works can be generally used for making other TMDC-based nanoelectronic and photonic devices, and the obtained device physics knowledge is anticipated to greatly leverage the uniquely advantageous optoelectronic properties of semiconducting TMDCs for enabling new device applications.

Published
2016

9. Multiple MoS2 Transistors for Sensing Molecule Interaction Kinetics.

Author

Nam, Hongsuk, Oh, Bo-Ram, Chen, Pengyu, Chen, Mikai, Wi, Sungjin, Kurabayashi, Katsuo, Liang, Xiaogan, and Wan, Wenjie

Subjects
FIELD-effect transistors, MOLYBDENUM disulfide, BIOSENSORS, INTERMOLECULAR interactions, TUMOR necrosis factors
Abstract

Atomically layered transition metal dichalcogenides (TMDCs) exhibit a significant potential to enable next-generation low-cost transistor biosensors that permit single-molecule-level quantification of biomolecules. To realize such potential biosensing capability, device-oriented research is needed for calibrating the sensor responses to enable the quantification of the affinities/kinetics of biomolecule interactions. In this work, we demonstrated MoS2-based transistor biosensors capable of detecting tumor necrosis factor - alpha (TNF-α) with a detection limit as low as 60 fM. Such a detection limit was achieved in both linear and subthreshold regimes of MoS2 transistors. In both regimes, all sets of transistors exhibited consistent calibrated responses with respect to TNF-α concentration, and they resulted in a standard curve, from which the equilibrium constant of the antibody-(TNF-α) pair was extracted to be KD = 369 ± 48 fM. Based on this calibrated sensor model, the time-dependent binding kinetics was also measured and the association/dissociation rates of the antibody-(TNF-α) pair were extracted to be (5.03 ± 0.16) × 108 M−1s−1 and (1.97 ± 0.08) × 10−4 s−1, respectively. This work advanced the critical device physics for leveraging the excellent electronic/structural properties of TMDCs in biosensing applications as well as the research capability in analyzing the biomolecule interactions with fM-level sensitivities. [ABSTRACT FROM AUTHOR]

Published
2015
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