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Search Publications by: Nhan Van Nguyen (Assoc)

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Displaying 1 - 25 of 96

Tailoring the High-K Gate Dielectric/Sillicon Interface for CMOS Applications

October 12, 2021
Y S. Lin, R Puthenkovilakam, J P. Chang, C P. Bouldin, Igor Levin, Nhan Van Nguyen, Y Sun, P Pianetta, T Conard, W Vandervorst, V Venturo, S Selbrede
The interfacial properties, thermal stabilities, and the electrical characteristics of ZrO 2/ Si and ZrO 2/SiO 2/Si were investigated and the interfacial layer of as-deposited ZrO 2 on silicon is likely to be ZrSi xO y. The ZrO 2/ZrSi xO y/Si is

Unraveling the compositional heterogeneity and carrier dynamics of alkali cation doped 3D/2D perovskites with improved stability

December 11, 2020
Ming Chun Tang, Siyuan Zhang, Nhan V. Nguyen, Edwin J. Heilweil, Christina A. Hacker, Timothy J. Magnanelli, Thomas D. Anthopoulos
Preventing the degradation of hybrid perovskite by humid air remains a challenge for their future commercial utilization. 3D/2D perovskites with hierarchical architecture have attracted significant attention due to their promising power conversion

Role of alkali-metal cations in electronic structure and halide segregation of hybrid perovskites

July 1, 2020
Siyuan Zhang, Ming Chun Tang, Yuanyuan Fan, Ruipeng Li, Nhan V. Nguyen, Kui Zhao, Thomas D. Anthopoulos, Christina A. Hacker
Triple-cation hybrid perovskites with mixed-halide have become one of the most dominant composition due to superior photovoltaic performance and stability. In this study, we systematically investigate the incorporation of cesium (Cs+) and potassium (K+) at

Efficient hybrid mixed-ion perovskite photovoltaics: in situ diagnostics of the roles of cesium and potassium alkali cation addition

June 19, 2020
Ming Chun Tang, Yuanyuan Fan, Dounya Barrit, Ruipeng Li, Hoang X. Dang, Siyuan Zhang, Timothy J. Magnanelli, Nhan V. Nguyen, Edwin J. Heilweil, Christina A. Hacker, Detlet-M Smilgies, Kui Zhao, Aram Amassian, Thomas D. Anthopoulos
Perovskite photovoltaics have made extraordinary progress in efficiency and stability in the past few years owing to process and formulation developments like antisolvent drip and mixed-cation mixed-halide compositions. Perovskite solar cells performance

Dielectric properties of Nb_x}W_1-x}Se_2} alloys

December 16, 2019
Albert Rigosi, Heather M. Hill, Sergiy Krylyuk, Nhan V. Nguyen, Angela Hight Walker, Albert Davydov, David Newell
The growth of transition metal dichalcogenide (TMDC) alloys provides an opportunity to experimentally access information elucidating how optical properties change with gradual substitutions in the lattice compared with their pure compositions. In this work

Computational screening of high-performance optoelectronic materials using OptB88vdW and TB-mBJ formalisms

May 8, 2018
Kamal Choudhary, Qin Zhang, Sugata Chowdhury, Nhan V. Nguyen, Zachary T. Trautt, Marcus W. Newrock, Faical Y. Congo, Andrew C. Reid, Francesca M. Tavazza
We perform high-throughput density functional theory (DFT) calculations for optoelectronic properties (electronic bandgap and frequency dependent dielectric function) using the OptB88vdW functional (OPT) and the Tran-Blaha modified Becke Johnson potential

Band offset and electron affinity of MBE-grown SnSe2

January 25, 2018
Qin Zhang, Mingda Li, Edward Lochocki, Suresh Vishwanath, Xinyu Liu, Rusen Yan, Huai-Hsun Lien, Malgorzata Dobrowolska, Jacek Furdyna, Kyle M. Shen, Guangjun Cheng, Angela R. Hight Walker, David J. Gundlach, Huili G. Xing, Nhan V. Nguyen
SnSe2 is currently considered a potential 2D material that can form a near-broken gap heterojunction in a tunnel field-effect transistor (TFET) due to its conceivable large electron affinity, which is experimentally confirmed in this letter. With the

Measuring the dielectric and optical response of millimeter-scale amorphous and hexagonal boron nitride films grown on epitaxial graphene

December 1, 2017
Albert F. Rigosi, Heather M. Hill, Nicholas R. Glavin, Sujitra J. Pookpanratana, Yanfei Yang, Alexander G. Boosalis, Jiuning Hu, Anthony Rice, Andrew A. Allerman, Nhan V. Nguyen, Christina A. Hacker, Randolph E. Elmquist, Angela R. Hight Walker, David B. Newell
Monolayer epitaxial graphene (EG), grown on the Si face of SiC, is an advantageous material for a variety of electronic and optical applications. EG forms as a single crystal over millimeter- scale areas and consequently, the large scale single crystal can

Probing the dielectric response of the interfacial buffer layer in epitaxial graphene via optical spectroscopy

November 28, 2017
Heather M. Hill, Albert Rigosi, Sugata Chowdhury, Yanfei Yang, Nhan Van Nguyen, Francesca Tavazza, Randolph Elmquist, David B. Newell, Angela R. Hight Walker
Monolayer epitaxial graphene (EG) is a suitable candidate for a variety of electronic applications. One advantage of EG growth on the Si face of SiC is that it develops as a single crystal, as does the layer below, referred to as the interfacial buffer

Band Alignment Measurement by Internal Photoemission Spectroscopy

January 30, 2017
Nhan V. Nguyen
parameters affecting the performance of advanced electronic and optoelectronic devices. Among the common band offset measurement techniques, internal photoemission has been proven to be a novel method which is almost a direct measurement without

Windowless CdSe/CdTe Solar Cells with Differentiated Back Contacts: J-V, EQE and Photocurrent Mapping

August 26, 2016
Daniel Josell, Ratan K. Debnath, Jong Yoon Ha, Jonathan E. Guyer, Nhan V. Nguyen, M. A. Sahiner, C Reehil, W. A. Manners
This paper presents a study of windowless CdSe/CdTe thin film photovoltaic devices with in-plane patterning at a submicrometer length scale. The photovoltaic cells are fabricated upon two interdigitated comb electrodes pre-patterned at micrometer length

An Antimony Selenide Molecular Ink for Flexible Broadband Photodetectors

August 3, 2016
Ratan K. Debnath, MD R. Hasan, Arunima Singh, Vladimir P. Oleshko, Shiqi Guo, Asha Rani, Abhishek Motayed, Nhan V. Nguyen, Albert Davydov
The need for low-cost high-performance broadband photon detection with sensitivity in the near infrared (NIR) has driven interest in new materials that combine high absorption with traditional electronic infrastructure (CMOS) compatibility. Here, we

High-performing visible-blind photodetectors based on SnO2/CuO nanoheterojunctions

December 14, 2015
Ratan K. Debnath, Ting Xie, MD R. Hasan, Nhan V. Nguyen, Abhishek Motayed
We report on the significant performance enhancement of SnO2 thin film ultraviolet (UV) photodetectors (PDs) through incorporation of CuO/SnO2 pn nanoscale heterojuctions. The nanoheterojunctions are self-assembled by sputtering Cu clusters that oxidize in

Broadband Optical Properties of Graphene by Spectroscopic Ellipsometry

December 11, 2015
Wei Li, Nhan Van Nguyen, Guangjun Cheng, Angela R. Hight Walker, David J. Gundlach, Yiran Liang, boyuan Tian, Xuelei Liang, Lian-Mao Peng
The broadband (0.7 eV to 9.0 eV) optical properties of chemical-vapor-deposition (CVD) grown graphene are determined by spectroscopic ellipsometry. The optical absorption follows the fine structure constant in the energy range from 1.0 eV to 2.0 eV, but

Exciton-dominated Dielectric Function of Atomically Thin MoS2 Films

November 24, 2015
Yilin Yu, Yifei Yu, Yongqing Cui, Wei Li, Gurarslan Alper, Peelaers Hartwin, Aspnes David, Chris Van de Walle, Nhan Van Nguyen, Zhang Yong-Wei, Linyou Cao
The control of photons by field effects, like the gating of electrons, can revolutionize a wide range of fields by enabling active photonic devices whose functions could be manipulated with sophistication and speeds comparable to what achieved in modern

An apparatus for spatially resolved, temperature dependent near infrared reflectance measurements for identifying thermochromic transitions in combinatorial thin film libraries

November 18, 2015
Sara C. Barron, Nam T. Nguyen, Nhan V. Nguyen, Martin L. Green, Mitul P. Patel
A metrology and data analysis protocol is described for high throughput construction of thermochromic metal-insulator phase diagrams for lightly substituted VO2 thin films. The technique exploits the abrupt change in near infrared optical properties

Self-powered p-NiO/n-ZnO heterojunction ultraviolet photodetectors fabricated on plastic substrates

October 1, 2015
Ratan K. Debnath, MD R. Hasan, Ting Xie, Sara C. Barron, Guannan Liu, Nhan V. Nguyen, Abhishek Motayed, M V. Rao
A self-powered ultraviolet (UV) photodetector (PD) based on p-NiO and n-ZnO was fabricated using low-temperature sputtering technique on indium doped tin oxide (ITO) coated plastic polyethylene terephthalate (PET) substrates. The fabricated devices showed

Solution-processed high-efficiency p-NiO/n-ZnO heterojunction photodetector

January 19, 2015
Ratan K. Debnath, Ting Xie, Baomei Wen, Wei Li, Abhishek Motayed, Nhan V. Nguyen
This paper presents a high efficiency heterojunction p-NiO/n-ZnO thin film ultraviolent (UV) photodetector fabricated on conductive glass substrates. The devices are fabricated by using a simple spin-coating layer-by-layer method from precursor solutions

Electron and Hole Photoemission Detection for Band Offset Determination of Tunnel Field-Effect Transistor Heterojunctions

November 24, 2014
Wei Li, Qin Zhang, R. Bijesh, Oleg A. Kirillov, Yiran Liang, Igor Levin, Lianmao Peng, Xuelei Liang, S. Datta, David J. Gundlach, Nhan V. Nguyen
The electrical performance of a tunnel field-effect transistor depends critically on the band offset at their semiconductor heterojunction interface. Historically, it has been difficult to experimentally determine how the electronic bands align at the