Article
Chemistry, Multidisciplinary
Jeevesh Kumar, Utpreksh Patbhaje, Mayank Shrivastava
Summary: The study captures the Raman scattering of breathing modes in multiple phosphorene flakes at different temperatures and estimates a negative temperature coefficient. It explores the unique feature of phonon scattering with temperature, showing a transition from three-phonon process scattering to four-phonon process scattering. The study highlights the significant dependency of the breathing modes on temperature, aiding in understanding and modeling phosphorene's interlayer thermal and mechanical properties.
Article
Nanoscience & Nanotechnology
Xujun Wang, Quanjie Wang, Xinyu Liu, Zixuan Huang, Xiangjun Liu
Summary: Grain boundaries in black phosphorene have significant effects on thermal boundary resistance and induce high thermal resistances and thermal rectification effects. The localization of phonons and strong phonon boundary scattering at the grain boundary area are found to be responsible for the high thermal resistance. The partial phonon modes exhibit weak localization in the presence of grain boundaries.
Article
Chemistry, Multidisciplinary
Shi-Qi Li, Xiangjun Liu, Xujun Wang, Hongsheng Liu, Gang Zhang, Jijun Zhao, Junfeng Gao
Summary: Edge termination is crucial for determining the properties of 2D materials. Ab initio simulations reveal a lowest-energy U-edge [ZZ(U)] reconstruction in bilayer phosphorene, reducing edge energy significantly and potentially dominating. Although ZZ(U) changes the topology of phosphorene nanoribbons, it is difficult to be identified through microscopy images. This edge reconstruction also enhances the thermal conductivity of PNR significantly compared with pristine and Klein edges.
Article
Materials Science, Multidisciplinary
Xiaolong Yang, Zhe Liu, Fanchen Meng, Wu Li
Summary: Recent studies have shown the significance of electron-phonon interaction (EPI) in phonon transport at intermediate temperatures, where EPI can dominate over anharmonic phonon-phonon scattering in some metals, leading to an anomalous phonon transport regime. Using first-principles calculations, it was predicted that in bilayer graphene, tuning the doping level can drive phonon transport into the anomalous regime, resulting in a fivefold reduction of lattice thermal conductivity at room temperature. The origin of this anomalous behavior lies in mirror symmetry breaking, dominance of normal processes in anharmonic ph-ph scattering, and the indirect effect of EPI on K-L.
Article
Multidisciplinary Sciences
Zhongtao Lin, Wuguo Liu, Shibing Tian, Ke Zhu, Yuan Huang, Yang Yang
Summary: By using Raman spectroscopy, the thermal expansion coefficients of suspended MoS2 and supported MoS2 were investigated, showing significant differences. Additionally, negative thermal expansion coefficients were observed in MoS2 below 175K, which is attributed to bending vibrations in the layer during cooling. This study demonstrates that Raman spectroscopy is a useful tool in exploring the thermal properties of few-layer MoS2 for potential application in photoelectronic devices.
SCIENTIFIC REPORTS
(2021)
Article
Physics, Multidisciplinary
Gang Liu, Hui Wang, Guo-Ling Li
Summary: The study found that all 2D materials exhibit negative thermal expansion properties at low temperatures, with only the monolayer retaining negative thermal expansion as temperature increases. As the number of layers increases, the negative thermal expansion of 2D materials weakens, due to changes in the Gruneisen parameter. Additionally, the temperature-dependent elastic properties were also investigated.
Article
Chemistry, Physical
Xiaowei Wang, Guangming Niu, Jutao Jiang, Laizhi Sui, Xiangyu Zeng, Xin Liu, Yutong Zhang, Guorong Wu, Kaijun Yuan, Xueming Yang
Summary: This study investigates the ultrafast carrier dynamics in Mo0.5W0.5S2 alloys using femtosecond transient absorption spectroscopy. An anomalous rebleaching of the ground state is observed at high pump fluence, which is attributed to carriers trapped in defects being thermally excited back to the untrapped exciton state.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Physics, Applied
Ryo Yokogawa, Yasutomo Arai, Ichiro Yonenaga, Motohiro Tomita, Sylvia Yuk Yee Chung, Hiroshi Uchiyama, Takanobu Watanabe, Atsushi Ogura
Summary: This study reports on the behavior of acoustic phonon spectral linewidth in Si1-xGex alloy with different compositions. Broadening of both transverse acoustic and longitudinal acoustic modes was observed, with the broadening of TA mode depending on the Ge fraction. Molecular dynamics simulations confirmed the experimental observations. These results indicate that the change in acoustic phonon spectral linewidth between Γ and X points is related to the appearance of localized modes in the alloy, leading to suppression of thermal transport.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Physical
W. M. Uvin G. De Alwis, Kevin L. Shuford
Summary: In this study, the optical properties of edge-passivated monolayer phosphorene quantum dots were analyzed using density functional theory and time-dependent density functional theory calculations. The results showed that optical absorptions and emissions preferred to occur from the armchair direction of phosphorene, regardless of edge functionalization or system size, making it a potential natural linear optical polarizer in the UV-vis region. Larger phosphorene quantum dots exhibited smaller Stokes shifts and less geometric variation upon relaxation, resulting in decreased radiative lifetimes.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Chemistry, Multidisciplinary
Faridul Islam, Arash Tahmasebi, Behdad Moghtaderi, Jianglong Yu
Summary: This study focused on synthesizing few-layer graphene (FLG) from bituminous coal through a catalytic process under microwave heat treatment. The research indicated that the catalyst percentages affected the structural change of FLG composite materials, and the catalyst loaded samples showed homogeneous distribution and indicated few-layer graphene sheets.
Article
Nanoscience & Nanotechnology
Ziqi Li, Bo Peng, Miao-Ling Lin, Yu-Chen Leng, Bin Zhang, Chi Pang, Ping-Heng Tan, Bartomeu Monserrat, Feng Chen
Summary: Research shows that phonons driven by femtosecond lasers can be utilized to manipulate the excitonic properties of semiconductors at THz frequencies, combining ultralow frequency Raman spectroscopy to identify phonon mode-selective and electron-phonon interactions. Furthermore, different types of coherent phonon excitations can preferentially couple to different types of electronic excitations.
NPJ 2D MATERIALS AND APPLICATIONS
(2021)
Article
Materials Science, Multidisciplinary
Anudeepa Ghosh, Mainak Palit, Sujan Maity, Vivek Dwij, Sumesh Rana, Subhadeep Datta
Summary: Temperature-dependent Raman spectroscopic studies on FePS3 reveal spin-phonon coupling, spin ordering, and magnon excitation phenomena as temperature decreases. Raman spectroscopy can predict the magnetic transition temperature of magnetic insulators and track magnon transport in heterostructures involving different electronic and magnetic orderings.
Article
Physics, Applied
Lu Zhao, Lijuan Zhang, Houfu Song, Hongda Du, Junqiao Wu, Feiyu Kang, Bo Sun
Summary: In this study, natural van der Waals (SnS)(1.17)(NbS2)(n) superlattices were synthesized and their thermal conductivities were measured. The results showed that heat conduction in these superlattices is primarily controlled by interface scattering, even when the superlattice period is atomically thin and abrupt. This finding provides valuable insights into the thermal behavior of van der Waals superlattices and offers approaches for effective thermal management depending on the specific types of interfaces.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Physical
Shihao Han, Qinghang Tang, Hongmei Yuan, Yufeng Luo, Huijun Liu
Summary: This study focuses on the phonon transport properties of Weyl semimetals TaAs and NbAs, and compares them by explicitly considering the electron-phonon coupling (EPC) in first-principles calculations. The results show that the EPC significantly reduces the lattice thermal conductivities of both systems, with a more pronounced effect in TaAs compared to NbAs at the same carrier concentration. Detailed analysis reveals that TaAs has a smaller EPC phonon relaxation time, characterized by stronger EPC strength related to larger deformation potential constant and Born effective charge. Additionally, the overlap between the EPC relaxation time and intrinsic phonon-phonon scattering is larger in TaAs, further reducing the lattice thermal conductivity. This work highlights the vital importance of EPC in accurately predicting phonon transport behaviors and provides a simple alternative to evaluate the EPC strength of different material systems.
JOURNAL OF MATERIOMICS
(2023)
Article
Materials Science, Multidisciplinary
Zhongwei Zhang, Yangyu Guo, Marc Bescond, Masahiro Nomura, Sebastian Volz, Jie Chen
Summary: In this paper, a theoretical model for exploring phonon coherence based on spectroscopy is proposed and validated using Brillouin light scattering data and molecular dynamic simulations. The model shows that confined modes exhibit wavelike behavior with a higher ratio of coherence time to lifetime. The spectroscopy data also demonstrates the dependence of phonon coherence on system size. The proposed model allows for reassessing conventional spectroscopy data to obtain coherence times, which are crucial for understanding and estimating phonon characteristics and heat transport in solids.
Article
Chemistry, Multidisciplinary
Mei Er Pam, Sifan Li, Tong Su, Yu-Chieh Chien, Yesheng Li, Yee Sin Ang, Kah-Wee Ang
Summary: This study demonstrates a facile approach to transform an inactive rhenium disulfide (ReS2) into an effective switching material through interfacial modulation induced by molybdenum-irradiation (Mo-i) doping. The results show that ReS2 of various thicknesses can be switchable by modulating the Mo-irradiation period. The fabricated device exhibits bipolar non-volatile switching, programmable multilevel resistance states, and long-term synaptic plasticity. Additionally, it achieves a high MNIST learning accuracy of 91% under a non-identical pulse train.
ADVANCED MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Yesheng Li, Shuai Chen, Zhigen Yu, Sifan Li, Yao Xiong, Mer-Er Pam, Yong-Wei Zhang, Koh-Wee Ang
Summary: This paper presents a low-voltage memristor array based on an ultrathin PdSeOx/PdSe2 heterostructure switching medium, which solves the problem of random ion transport in traditional memristors, achieving remarkable uniform switching with low variability. Convolutional image processing with high recognition accuracy was also achieved by using various crossbar kernels.
ADVANCED MATERIALS
(2022)
Review
Green & Sustainable Science & Technology
Z. Y. Yeo, Z. P. Ling, J. W. Ho, Q. X. Lim, Y. H. So, S. Wang
Summary: This article discusses the stability issues of silicon-based solar cells under sunlight illumination and the research on improving performance through the use of alternative silicon materials and regeneration technologies. The results show that the performance of solar cells significantly improves after the regeneration process.
RENEWABLE & SUSTAINABLE ENERGY REVIEWS
(2022)
Article
Nanoscience & Nanotechnology
Bochang Li, Wei Wei, Li Luo, Ming Gao, Zhi Gen Yu, Sifan Li, Kah-Wee Ang, Chunxiang Zhu
Summary: A novel electrochemical metallization memristor based on solution-processed Pt/CuI/Cu structure is proposed and demonstrated in this work. It has high resistance switching ratio and low power consumption, enabling Boolean logic operations and image encryption and decryption.
ADVANCED ELECTRONIC MATERIALS
(2022)
Article
Energy & Fuels
Z. P. Ling, Q. X. Lim, K. N. Lim, J. W. Ho, S. Wang
Summary: This study compares the performance of solar modules comprised of p-PERC silicon solar cells that have undergone advanced hydrogenation treatment with those that have not. The results show that advanced hydrogenation technology effectively addresses the issues of light-induced degradation and light-and elevated-temperature induced degradation, resulting in higher power generation capability for the hydrogenated solar arrays.
SOLAR ENERGY MATERIALS AND SOLAR CELLS
(2022)
Article
Multidisciplinary Sciences
Viacheslav Sorkin, Hangbo Zhou, Zhi Gen Yu, Kah-Wee Ang, Yong-Wei Zhang
Summary: In this study, the effects of different types, locations, and densities of point defects in monolayer MoS2 on the electronic structures and Schottky barrier heights (SBH) of Au/MoS2 heterojunction are investigated using DFT calculations. The results show that the SBH of monolayer MoS2 with defects is universally higher than that of the defect-free counterpart. Specifically, S divacancy and Mo-S antisite defects have a larger effect on increasing the SBH compared to S monovacancy. Defects located in the inner sublayer of MoS2 also have a larger impact on the SBH than those in the outer sublayer. Increasing defect density leads to a higher SBH. These findings provide practical guidelines for controlling and optimizing the SBH in Au/MoS2 heterojunctions through defect engineering.
SCIENTIFIC REPORTS
(2022)
Review
Chemistry, Multidisciplinary
Jun-young Kim, Xin Ju, Kah-Wee Ang, Dongzhi Chi
Summary: Two-dimensional materials have attracted attention for their potential in scientific breakthroughs and technological innovations. The integration of 2DMs on Si CMOS platform or flexible electronics has gained interest for applications such as back-end-of-line transistors, memory devices/ selectors, and sensors. The successful transfer of 2DM layers from growth substrate to Si is crucial for these applications, and various transfer methods leveraging van der Waals transfer capability have been developed. This review surveys and compares these transfer methods, focusing on 2D TMDC film transfer and 2DM template-assisted van der Waals growth/transfer of non-2D thin films.
Article
Chemistry, Multidisciplinary
Yu-Chieh Chien, Heng Xiang, Yufei Shi, Ngoc Thanh Duong, Sifan Li, Kah-Wee Ang
Summary: The study demonstrates a hafnium oxide-based ferroelectric encoder for temporal-efficient information processing in SNN. This high-performance ferroelectric encoder features superior switching efficiency and robust ferroelectric response, achieving a broad dynamic range.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Heng Xiang, Yu-Chieh Chien, Lingqi Li, Haofei Zheng, Sifan Li, Ngoc Thanh Duong, Yufei Shi, Kah-Wee Ang
Summary: This study demonstrates the capabilities of an integrated ferroelectric HfO2 and 2D MoS2 channel FeFET for achieving high-performance 4-bit per cell memory and low variation and power consumption synapses. The device retains the ability to implement diverse learning rules and accurately recognizes MNIST handwritten digits with over 94% accuracy using online training mode. These results highlight the potential of FeFET-based in-memory computing for future neuromorphic computing applications.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Yu-Chieh Chien, Heng Xiang, Jianze Wang, Yufei Shi, Xuanyao Fong, Kah-Wee Ang
Summary: By harnessing the physically unclonable properties, true random number generators (TRNGs) can generate random bitstreams that are cryptographically secured, alleviating security concerns. However, conventional hardware often shows predictable patterns susceptible to machine learning attacks. This paper presents a low-power self-corrected TRNG based on molybdenum disulfide ferroelectric field-effect transistors, which exhibits enhanced stochastic variability and passes machine learning attacks, as well as statistical tests.
Article
Automation & Control Systems
Ngoc Thanh Duong, Yu-Chieh Chien, Heng Xiang, Sifan Li, Haofei Zheng, Yufei Shi, Kah-Wee Ang
Summary: A 1D array of Fe-FET based on alpha-In2Se3 channel is demonstrated, which exhibits volatile memory effect and is capable of implementing various RC systems. It achieves high accuracy in image classification and accurate forecasting of real-life chaotic systems such as weather.
ADVANCED INTELLIGENT SYSTEMS
(2023)
Article
Chemistry, Multidisciplinary
Zhengjin Weng, Haofei Zheng, Wei Lei, Helong Jiang, Kah-Wee Ang, Zhiwei Zhao
Summary: This study demonstrates the successful fabrication of high-yield, high-performance, and uniform memristors using a single-crystalline few-layered manganese phosphorus trisulfide (MnPS3) as a resistive switching medium. The memristors exhibit desired characteristics for neuromorphic computing and achieve a high accuracy of 95.15% in supervised learning using the MNIST handwritten recognition dataset. This research is significant for experimental studies on memristors.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
Yangwu Wu, Ngoc Thanh Duong, Yu-Chieh Chien, Song Liu, Kah-Wee Ang
Summary: Neuromorphic computing, specifically reservoir computing (RC), is an effective approach for time-series analysis and forecasting in economics and engineering. In this study, a synapse device based on CuInP2S6 (CIPS) material is demonstrated, achieving synaptic performance emulation and temporal dynamics under electrical stimulation. The migration of Cu+ ions in CIPS is controlled, and the device exhibits low normalized root mean square errors (NRMSE) for various tasks, highlighting the potential of CIPS for real-time signal processing and expanding applications in neuromorphic computing.
ADVANCED ELECTRONIC MATERIALS
(2023)
Article
Engineering, Electrical & Electronic
Xinke Liu, Yuheng Lin, Zhichen Lin, Jiangchuan Wang, Ziyue Zhang, Yugeng Li, Xiaohua Li, Deliang Zhu, Kah-Wee Ang, Ming Fang, Wangying Xu, Qi Wang, Wenjie Yu, Qiang Liu, Shuangwu Huang
Summary: The use of plasmonic structure enhances the performance of MoS2-based devices, and in this study, a plasmonic-enhanced few-layer MoS2 photodetector was successfully prepared on a GaN substrate, demonstrating high responsivity and low noise.
ACS APPLIED ELECTRONIC MATERIALS
(2022)
Review
Chemistry, Physical
Heng Xiang, Yu-Chieh Chien, Yufei Shi, Kah-Wee Ang
Summary: The security of Internet-of-Things (IoT) is crucial in various aspects such as device-to-device communication, sensing and actuating, and information exchange. Conventional cryptographic algorithms and silicon-based security primitives are constantly challenged by evolving attack methods, thus the implementation of hardware security using 2D materials is worth exploring. This review summarizes the research progress in 2D material-based true random number generators (TRNGs), physical unclonable functions (PUFs), and other security applications, and discusses entropy sources, reliability, circuit, and machine learning modeling attacks on TRNGs and PUFs.