Article
Chemistry, Multidisciplinary
Connor J. McClellan, Eilam Yalon, Kirby K. H. Smithe, Saurabh Suryavanshi, Eric Pop
Summary: This study demonstrates a method of low-temperature substoichiometric AlOx doping for monolayer MoS2, achieving high carrier densities and low sheet resistance in transistors. The doped MoS2 devices approach several low-power transistor metrics required by the international technology roadmap, making them promising for future semiconductor applications.
Article
Chemistry, Multidisciplinary
Isha M. Datye, Alwin Daus, Ryan W. Grady, Kevin Brenner, Sam Vaziri, Eric Pop
Summary: Strain can significantly enhance the electron mobility of two-dimensional semiconductors, which is crucial for applications such as flexible strain sensors.
Article
Chemistry, Physical
Robert T. Busch, Riccardo Torsi, Angelica Drees, David Moore, Andrew Sarangan, Nicholas R. Glavin, Joshua A. Robinson, Jonathan P. Vernon, W. Joshua Kennedy, Peter R. Stevenson
Summary: The optical behavior of two-dimensional transition metal dichalcogenides (TMDCs) is influenced by thickness and lateral quantum confinement effects. In this study, the optical properties of monolayer metalorganic chemical vapor deposited MoS2 were evaluated using ex situ spectroscopic ellipsometry. The analysis demonstrated the ability to probe the optical exciton behavior of MoS2 at growth-relevant grain sizes and provided insights into the effects of chemical vapor nucleation density, ripening, and lateral growth conditions on the optical properties.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Chemistry, Physical
Robert T. Busch, Riccardo Torsi, Angelica Drees, David Moore, Andrew Sarangan, Nicholas R. Glavin, Joshua A. Robinson, Jonathan P. Vernon, W. Joshua Kennedy, Peter R. Stevenson
Summary: This study evaluates laterally coalescing monolayer MoS2 films using ex situ spectroscopic ellipsometry and demonstrates the ability to probe optical exciton behavior at growth-relevant grain sizes. It provides insights for the in situ epitaxial growth of 2D TMDC films with targeted optical properties.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Nanoscience & Nanotechnology
J. Liu, P. Sestak, Z. Zhang, J. Wu
Summary: The study investigates the response of monolayer MoS2 with pentagon-heptagon (5|7) pair defect-dominated grain boundary under in-plane tension using first-principles calculations. It is found that the brittle or ductile behavior depends on the GB tilt angle, and the failure strength can increase with increasing 5|7 dislocation defect. Surprisingly, the 5|7 dislocation defects can be annihilated by stretching to form defect-free MoS2.
MATERIALS TODAY NANO
(2022)
Article
Materials Science, Multidisciplinary
Fabio Caruso, Patrick Amsalem, Jie Ma, Areej Aljarb, Thorsten Schultz, Marios Zacharias, Vincent Tung, Norbert Koch, Claudia Draxl
Summary: Experimental and theoretical evidence of strong electron-plasmon interaction in n-doped single-layer MoS2 has been reported. The emergence of distinctive signatures of polaronic coupling in the electron spectral function was revealed through angle-resolved photoemission spectroscopy measurements. Calculations based on many-body perturbation theory illustrated that electronic coupling to two-dimensional carrier plasmons provides an exhaustive explanation of the experimental spectral features and their energies.
Article
Multidisciplinary Sciences
Amritanand Sebastian, Rahul Pendurthi, Tanushree H. Choudhury, Joan M. Redwing, Saptarshi Das
Summary: The study benchmarks device-to-device variation in FETs based on MoS2 and WS2, showing consistent performance and record high carrier mobility in WS2 FETs.
NATURE COMMUNICATIONS
(2021)
Article
Chemistry, Multidisciplinary
Arijit Kayal, Sraboni Dey, G. Harikrishnan, Renjith Nadarajan, Shashwata Chattopadhyay, Joy Mitra
Summary: The extraordinary mechanical properties of two-dimensional transition-metal dichalcogenides make them ideal candidates for investigating strain-induced control of various physical properties. By exploring the role of nonuniform strain on semiconducting, chemical vapor deposited monolayer MoS2 on nanostructured substrates, this study investigates the modulation of optical, electronic, and transport properties. The findings demonstrate the accumulation of electron density at strained regions, leading to a significant increase in field effect mobility in strained samples. Furthermore, the study shows that the pattern-induced strain can be easily controlled by changing the periodicity of the nanostructures, providing a robust yet useful macroscopic control on strain and mobility in these systems.
Article
Chemistry, Multidisciplinary
Ruihao Sun, Shiyu Sun, Xiu Liang, Hongyu Gong, Xingshuang Zhang, Yong Li, Meng Gao, Dongwei Li, Guanchen Xu
Summary: This study selected 1,1,2,2-tetraphenylethylene (TPE) derivative molecules with aggregation-induced emission (AIE) effect as adjustable dopants to achieve controlled p/n-type doping on a chemical vapor deposition (CVD) grown monolayer, MoS2. The electron transfer behavior between these dopants and MoS2 was investigated through fluorescence, Raman, X-ray photoelectron spectra and transient absorption spectra. The experimental results were further explained and confirmed by density functional theory calculations. This work demonstrates a new way to select suitable dopants for TMDCs and has important implications for optoelectronic device applications.
Review
Chemistry, Physical
Zheng Wei, Qinqin Wang, Lu Li, Rong Yang, Guangyu Zhang
Summary: Monolayer MoS(2) as an emerging 2D semiconductor material has various promising applications. Epitaxy is a promising technique for producing high-quality, large-area MoS(2) with controllable properties. Future research will focus on large-scale films with large domain sizes and high domain alignments.
Article
Nanoscience & Nanotechnology
Huimin Hu, Jin-Ho Choi
Summary: This study systematically investigates the adsorption properties of atomic hydrogen on monolayer MoS2, revealing that the S-top site is the most energetically preferred. The tilting of the S-H bond and the effects of spin-polarization play significant roles in determining the adsorption energies and configurations.
Article
Chemistry, Physical
Jiankun Xiao, Zhuo Kang, Baishan Liu, Xiankun Zhang, Junli Du, Kuanglei Chen, Huihui Yu, Qingliang Liao, Zheng Zhang, Yue Zhang
Summary: High contact resistance in monolayer MoS2 transistors limits their electrical performance, but a proposed end-bond contact scheme achieves ultra-low contact resistance and high-performance saturation current density.
Article
Chemistry, Physical
Yaping Miao, Hongwei Bao, Wei Fan, Yan Li, Fei Ma
Summary: The study reveals that N doping has a significant impact on the adsorption behaviors of atoms and gas molecules on MoS2 monolayer, such as enhancing the adsorption sensitivity of NH3 and NO2 molecules and improving the adsorption energy. Additionally, it is found that N doping effectively reduces the migration barrier of NO2 gas molecules on MoS2.
SURFACES AND INTERFACES
(2021)
Article
Nanoscience & Nanotechnology
Alvin Tang, Aravindh Kumar, Marc Jaikissoon, Krishna Saraswat, H-S Philip Wong, Eric Pop
Summary: This study demonstrates the synthesis of continuous monolayer MoS2 films at a relatively low temperature using direct CVD solid-source precursors, achieving high mobility and excellent current characteristics in transistor measurements. This offers a pathway towards high-quality, thermal-budget-compatible 2D semiconductors for heterogeneous integration with silicon manufacturing.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Chemistry, Multidisciplinary
Sangyeon Pak, Seunghun Jang, Taehun Kim, Jungmoon Lim, Jae Seok Hwang, Yuljae Cho, Hyunju Chang, A-Rang Jang, Kyung-Ho Park, John Hong, SeungNam Cha
Summary: The study presents an innovative device configuration with metallic CuS electrodes to induce self-healing of sulfur vacancy defects in the MoS2 channel, leading to significantly improved device performance. The self-healed MoS2 transistors with CuS electrodes exhibit outstanding room temperature mobility and photoresponsivity, demonstrating a promising strategy for high performance TMDCs-based devices.
ADVANCED MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Timothy D. Brown, Stephanie M. Bohaichuk, Mahnaz Islam, Suhas Kumar, Eric Pop, R. Stanley Williams
Summary: This study presents a model of VO2/SiN Mott threshold switches constructed using the principle of local activity. The model is refined to measurable material properties by considering a minimal set of quasistatic and dynamic electrical and thermal data. It accurately predicts electrical and thermal conductivities and capacitances, as well as locally active dynamics.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Asir Intisar Khan, Heshan Yu, Huairuo Zhang, John R. Goggin, Heungdong Kwon, Xiangjin Wu, Christopher Perez, Kathryn M. Neilson, Mehdi Asheghi, Kenneth E. Goodson, Patrick M. Vora, Albert Davydov, Ichiro Takeuchi, Eric Pop
Summary: Phase-change memory (PCM) is a promising candidate for data-intensive artificial intelligence applications, and achieving simultaneous attributes such as resistance changes and low resistance drift remains a challenge. In this study, nanoscale PCM devices based on a new phase-change nanocomposite material (Ge4Sb6Te7) demonstrated bi-directional gradual resistance changes with a large resistance window using low energy pulses. These devices showed multiple resistance levels with low resistance drift, high on/off ratio, and low variability, enabled by the unique properties of Ge4Sb6Te7. These findings advance the development of energy-efficient analog computing using PCM.
ADVANCED MATERIALS
(2023)
Article
Engineering, Electrical & Electronic
Cagil Koroglu, Eric Pop
Summary: As physical transistor scaling nears its limits and memory bandwidth becomes a bottleneck for many applications, three-dimensional (3D) integration offers a promising solution to continue Moore's law. Effective thermal management is essential to maximize the performance benefits of 3D integrated circuits (ICs), and using high thermal conductivity insulators like AlN and hBN can significantly reduce thermal resistance and overcome thermal challenges. In addition, highly anisotropic insulators such as hBN can be utilized as heat spreaders in memory-on-logic architectures to keep both memory and logic dies cool.
IEEE ELECTRON DEVICE LETTERS
(2023)
Article
Multidisciplinary Sciences
Weisheng Li, Xiaoshu Gong, Zhihao Yu, Liang Ma, Wenjie Sun, Si Gao, Cagil Koroglu, Wenfeng Wang, Lei Liu, Taotao Li, Hongkai Ning, Dongxu Fan, Yifei Xu, Xuecou Tu, Tao Xu, Litao Sun, Wenhui Wang, Junpeng Lu, Zhenhua Ni, Jia Li, Xidong Duan, Peng Wang, Yuefeng Nie, Hao Qiu, Yi Shi, Eric Pop, Jinlan Wang, Xinran Wang
Summary: By hybridizing with semi-metallic antimony (0112) through strong van der Waals interactions, the electrical contact of monolayer molybdenum disulfide is improved, meeting the requirements for the development of next-generation electronics.
Article
Engineering, Electrical & Electronic
Sumaiya Wahid, Alwin Daus, Jimin Kwon, Shengjun Qin, Jung-Soo Ko, H. -S. Philip Wong, Eric Pop
Summary: We report the performance and gate bias stress stability of ultrathin (similar to 4 nm) channel indium tin oxide (ITO) transistors using different precursors for atomic layer deposition (ALD) of the Al2O3 top-gate dielectric. Water-based ALD leads to devices remaining in the on-state, while ozone-based ALD devices have less negative V-T shift at short channel lengths and relatively more positive V-T at all channel lengths. We achieve maximum drive current and good gate bias stability with normalized VT shift, improving over previous reports of uncapped ITO transistors.
IEEE ELECTRON DEVICE LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Emanuel Ber, Ryan W. Grady, Eric Pop, Eilam Yalon
Summary: This article explores the issue of contact resistance in atomically thin 2-D semiconductors, which hinders the integration of these materials into mainstream technology. The resistance is found to be influenced by the height and width of the Schottky barrier, as well as the number of transport modes for carrier injection. To reduce the contact resistance, a large number of transport modes can be achieved by increasing the number of channel carriers through heavy doping or gating.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Chemistry, Multidisciplinary
Victoria Chen, Hye Ryoung Lee, Cagil Koroglu, Connor J. McClellan, Alwin Daus, Eric Pop
Summary: In this study, we characterized the electrical and thermoelectric properties of layered WSe2 with thicknesses ranging from 10 to 96 nm at temperatures between 300 and 400 K. By electrostatically gating the devices with an ion gel, we were able to investigate both electron and hole behavior over a wide range of carrier densities. The highest n- and p-type Seebeck coefficients for thin-film WSe2 at room temperature, -500 and 950 μV/K respectively, were obtained in this study. We also highlighted the significance of low substrate thermal conductivity for lateral thermoelectric measurements, which improves the platform for future studies on other nanomaterials.
Article
Chemistry, Multidisciplinary
Jie Zhao, Asir Intisar Khan, Mikhail Y. Efremov, Zichao Ye, Xiangjin Wu, Kangsik Kim, Zonghoon Lee, H. -S. Philip Wong, Eric Pop, Leslie H. Allen
Summary: The phase transition of Sb2Te3/Ge2Sb2Te5 superlattices was studied using nanocalorimetry, providing insights into the thermodynamics of superlattice-based PCM and enabling low-power switching.
Article
Physics, Applied
Stephanie M. Bohaichuk, Suhas Kumar, Mahnaz Islam, Miguel Munoz Rojo, R. Stanley Williams, Gregory Pitner, Jaewoo Jeong, Mahesh G. Samant, Stuart S. P. Parkin, Eric Pop
Summary: Oscillatory devices are important in biomimetic neuronal spiking computing systems, but understanding their time scales is challenging due to the influence of external circuitry. In this study, we demonstrate the challenges using a sub-100-nm VO2 Mott oscillator with a nanogap cut in a metallic carbon nanotube electrode. Despite its nanoscale thermal volume, external parasitics result in orders-of-magnitude slower dynamics. We discuss methods for determining when measurements are dominated by extrinsic factors and the conditions for observing intrinsic oscillation frequencies.
PHYSICAL REVIEW APPLIED
(2023)
Article
Nanoscience & Nanotechnology
Emanuel Ber, Ryan W. Grady, Eric Pop, Eilam Yalon
Summary: Achieving good electrical contacts is a major challenge in devices based on atomically thin 2D semiconductors. This study experimentally examines the classical transmission line model description of contacts to 2D materials and proposes a modification based on an additional lateral resistance component. It finds that the additional lateral resistance component dominates the contact resistance in atomically thin semiconductor devices and is responsible for the back-gate bias and temperature dependence.
ADVANCED ELECTRONIC MATERIALS
(2023)
Article
Optics
Qitong Li, Jung-Hwan Song, Fenghao Xu, Jorik van de Groep, Jiho Hong, Alwin Daus, Yan Joe Lee, Amalya C. Johnson, Eric Pop, Fang Liu, Mark L. Brongersma
Summary: A general pathway to reduce the detrimental impact of dephasing and non-radiative decay processes in quantum devices is illustrated through photonic design of device electrodes. The design enables large Purcell enhancement, convenient electrical gating, and high modulation efficiencies.
Article
Multidisciplinary Sciences
Joel Martis, Sandhya Susarla, Archith Rayabharam, Cong Su, Timothy Paule, Philipp Pelz, Cassandra Huff, Xintong Xu, Hao-Kun Li, Marc Jaikissoon, Victoria Chen, Eric Pop, Krishna Saraswat, Alex Zettl, Narayana R. Aluru, Ramamoorthy Ramesh, Peter Ercius, Arun Majumdar
Summary: Four-dimensional scanning transmission electron microscopy (4D-STEM) was used to determine the electron charge density in monolayer MoS2 by combining center of mass (CoM) images and annular dark field (ADF) images. The contribution of core electrons and valence electrons to the charge density was evaluated, with the core electrons mainly responsible for the spatial modulation and the valence electrons forming a featureless background. This study highlights the importance of probe shape in interpreting charge densities derived from 4D-STEM and suggests the need for smaller electron probes.
NATURE COMMUNICATIONS
(2023)
Article
Nanoscience & Nanotechnology
Aviv Schwarz, Hadas Alon-Yehezkel, Adi Levi, Rajesh Kumar Yadav, Koushik Majhi, Yael Tzuriel, Lauren Hoang, Connor S. Bailey, Thomas Brumme, Andrew J. Mannix, Hagai Cohen, Eilam Yalon, Thomas Heine, Eric Pop, Ori Cheshnovsky, Doron Naveh
Summary: Recent research on 2D transition metal dichalcogenides (TMDCs) has led to important discoveries in fundamental phenomena and device applications. In this study, a two-step treatment with organic molecules was used to heal native defects in CVD-grown WSe2 and WS2. The adsorption of thiols was found to only partially passivate defects, but molecular trimming and release of atomic sulfur significantly improved semiconductor quality. Time-dependent XPS and first-principles calculations were used to characterize defects and their healing.
NPJ 2D MATERIALS AND APPLICATIONS
(2023)
Article
Chemistry, Multidisciplinary
Timm Swoboda, Nicolas Wainstein, Sanchit Deshmukh, Cagil Koroglu, Xing Gao, Mario Lanza, Hans Hilgenkamp, Eric Pop, Eilam Yalon, Miguel Munoz Rojo
Summary: Heat dissipation is a major concern for electronic devices, especially at the nanoscale. Scanning thermal microscopy (SThM) is a versatile tool for measuring device temperature with nanoscale resolution but quantifying thermal features is challenging. This study calibrates a thermo-resistive SThM probe using metal lines of different widths and evaluates its sensitivity under different conditions. The results provide new insights for accurately determining the temperature of scanned devices.
Article
Materials Science, Multidisciplinary
Hon-Loen Sinn, Aravindh Kumar, Eric Pop, Akm Newaz
Summary: Researchers demonstrated a bismuth-1L-MoS2-bismuth device with ohmic electrical contacts and extraordinary optoelectronic properties by suppressing metal-induced gap states (MIGS) at the metal-monolayer MoS2 interface. This overcomes Fermi-level pinning and expands the application range of optoelectronic devices based on 2D transition metal dichalcogenides.
ADVANCED PHOTONICS RESEARCH
(2023)
