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1. Flexoelectric Thin-Film Photodetectors

Author

Wu, Ming, primary, Jiang, Zhizheng, additional, Lou, Xiaojie, additional, Zhang, Fan, additional, Song, Dongsheng, additional, Ning, Shoucong, additional, Guo, Mengyao, additional, Pennycook, Stephen J., additional, Dai, Ji-yan, additional, and Wen, Zheng, additional

Published
2021
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2. An Anomalous Magneto-Optic Effect in Epitaxial Indium Selenide Layers

Author

Fu, Wei, primary, Zhao, Xiaoxu, additional, Wang, Ke, additional, Chen, Zhi, additional, Leng, Kai, additional, Fu, Deyi, additional, Song, Peng, additional, Wang, Hai, additional, Deng, Longjiang, additional, Pennycook, Stephen J., additional, Zhang, Gang, additional, Peng, Bo, additional, and Loh, Kian Ping, additional

Published
2020
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3. High-Energy Gain Upconversion in Monolayer Tungsten Disulfide Photodetectors

Author

Wang, Qixing, primary, Zhang, Qi, additional, Zhao, Xiaoxu, additional, Zheng, Yu Jie, additional, Wang, Junyong, additional, Luo, Xin, additional, Dan, Jiadong, additional, Zhu, Rui, additional, Liang, Qijie, additional, Zhang, Lei, additional, Wong, P. K. Johnny, additional, He, Xiaoyue, additional, Huang, Yu Li, additional, Wang, Xinyun, additional, Pennycook, Stephen J., additional, Eda, Goki, additional, and Wee, Andrew T. S., additional

Published
2019
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4. Photoluminescence Upconversion by Defects in Hexagonal Boron Nitride

Author

Wang, Qixing, primary, Zhang, Qi, additional, Zhao, Xiaoxu, additional, Luo, Xin, additional, Wong, Calvin Pei Yu, additional, Wang, Junyong, additional, Wan, Dongyang, additional, Venkatesan, T., additional, Pennycook, Stephen J., additional, Loh, Kian Ping, additional, Eda, Goki, additional, and Wee, Andrew T. S., additional

Published
2018
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5. Molecular-Beam Epitaxy of Two-Dimensional In2Se3 and Its Giant Electroresistance Switching in Ferroresistive Memory Junction

Author

Poh, Sock Mui, primary, Tan, Sherman Jun Rong, additional, Wang, Han, additional, Song, Peng, additional, Abidi, Irfan H., additional, Zhao, Xiaoxu, additional, Dan, Jiadong, additional, Chen, Jingsheng, additional, Luo, Zhengtang, additional, Pennycook, Stephen J., additional, Castro Neto, Antonio H., additional, and Loh, Kian Ping, additional

Published
2018
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6. Mo-Terminated Edge Reconstructions in Nanoporous Molybdenum Disulfide Film

Author

Zhao, Xiaoxu, primary, Fu, Deyi, additional, Ding, Zijing, additional, Zhang, Yu-Yang, additional, Wan, Dongyang, additional, Tan, Sherman J. R., additional, Chen, Zhongxin, additional, Leng, Kai, additional, Dan, Jiadong, additional, Fu, Wei, additional, Geng, Dechao, additional, Song, Peng, additional, Du, Yonghua, additional, Venkatesan, T., additional, Pantelides, Sokrates T., additional, Pennycook, Stephen J., additional, Zhou, Wu, additional, and Loh, Kian Ping, additional

Published
2017
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9. Monolayer PtSe2, a New Semiconducting Transition-Metal-Dichalcogenide, Epitaxially Grown by Direct Selenization of Pt

Author

Wang, Yeliang, primary, Li, Linfei, additional, Yao, Wei, additional, Song, Shiru, additional, Sun, J. T., additional, Pan, Jinbo, additional, Ren, Xiao, additional, Li, Chen, additional, Okunishi, Eiji, additional, Wang, Yu-Qi, additional, Wang, Eryin, additional, Shao, Yan, additional, Zhang, Y. Y., additional, Yang, Hai-tao, additional, Schwier, Eike F., additional, Iwasawa, Hideaki, additional, Shimada, Kenya, additional, Taniguchi, Masaki, additional, Cheng, Zhaohua, additional, Zhou, Shuyun, additional, Du, Shixuan, additional, Pennycook, Stephen J., additional, Pantelides, Sokrates T., additional, and Gao, Hong-Jun, additional

Published
2015
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13. Molecular-Beam Epitaxy of Two-Dimensional In2Se3and Its Giant Electroresistance Switching in Ferroresistive Memory Junction

Author

Poh, Sock Mui, Tan, Sherman Jun Rong, Wang, Han, Song, Peng, Abidi, Irfan H., Zhao, Xiaoxu, Dan, Jiadong, Chen, Jingsheng, Luo, Zhengtang, Pennycook, Stephen J., Castro Neto, Antonio H., and Loh, Kian Ping

Abstract

Ferroelectric thin film has attracted great interest for nonvolatile memory applications and can be used in either ferroelectric Schottky diodes or ferroelectric tunneling junctions due to its promise of fast switching speed, high on-to-off ratio, and nondestructive readout. Two-dimensional α-phase indium selenide (In2Se3), which has a modest band gap and robust ferroelectric properties stabilized by dipole locking, is an excellent candidate for multidirectional piezoelectric and switchable photodiode applications. However, the large-scale synthesis of this material is still elusive, and its performance as a ferroresistive memory junction is rarely reported. Here, we report the low-temperature molecular-beam epitaxy (MBE) of large-area monolayer α-In2Se3on graphene and demonstrate the use of α-In2Se3on graphene in ferroelectric Schottky diode junctions by employing high-work-function gold as the top electrode. The polarization-modulated Schottky barrier formed at the interface exhibits a giant electroresistance ratio of 3.9 × 106with a readout current density of >12 A/cm2, which is more than 200% higher than the state-of-the-art technology. Our MBE growth method allows a high-quality ultrathin film of In2Se3to be heteroepitaxially grown on graphene, thereby simplifying the fabrication of high-performance 2D ferroelectric junctions for ferroresistive memory applications.

Published
2018
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14. Band Gap Engineering and Layer-by-Layer Mapping of Selenium-Doped Molybdenum Disulfide

Author

Gong, Yongji, primary, Liu, Zheng, additional, Lupini, Andrew R., additional, Shi, Gang, additional, Lin, Junhao, additional, Najmaei, Sina, additional, Lin, Zhong, additional, Elías, Ana Laura, additional, Berkdemir, Ayse, additional, You, Ge, additional, Terrones, Humberto, additional, Terrones, Mauricio, additional, Vajtai, Robert, additional, Pantelides, Sokrates T., additional, Pennycook, Stephen J., additional, Lou, Jun, additional, Zhou, Wu, additional, and Ajayan, Pulickel M., additional

Published
2013
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15. AC/AB Stacking Boundaries in Bilayer Graphene

Author

Lin, Junhao, primary, Fang, Wenjing, additional, Zhou, Wu, additional, Lupini, Andrew R., additional, Idrobo, Juan Carlos, additional, Kong, Jing, additional, Pennycook, Stephen J., additional, and Pantelides, Sokrates T., additional

Published
2013
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19. Tuning Structural and Mechanical Properties of Two-Dimensional Molecular Crystals: The Roles of Carbon Side Chains

Author

Cun, Huanyao, primary, Wang, Yeliang, additional, Du, Shixuan, additional, Zhang, Lei, additional, Zhang, Lizhi, additional, Yang, Bing, additional, He, Xiaobo, additional, Wang, Yue, additional, Zhu, Xueyan, additional, Yuan, Quanzi, additional, Zhao, Ya-Pu, additional, Ouyang, Min, additional, Hofer, Werner A., additional, Pennycook, Stephen J., additional, and Gao, Hong-jun, additional

Published
2012
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30. Molecular-Beam Epitaxy of Two-Dimensional In 2 Se 3 and Its Giant Electroresistance Switching in Ferroresistive Memory Junction.

Author

Poh SM, Tan SJR, Wang H, Song P, Abidi IH, Zhao X, Dan J, Chen J, Luo Z, Pennycook SJ, Castro Neto AH, and Loh KP

Abstract

Ferroelectric thin film has attracted great interest for nonvolatile memory applications and can be used in either ferroelectric Schottky diodes or ferroelectric tunneling junctions due to its promise of fast switching speed, high on-to-off ratio, and nondestructive readout. Two-dimensional α-phase indium selenide (In 2 Se 3 ), which has a modest band gap and robust ferroelectric properties stabilized by dipole locking, is an excellent candidate for multidirectional piezoelectric and switchable photodiode applications. However, the large-scale synthesis of this material is still elusive, and its performance as a ferroresistive memory junction is rarely reported. Here, we report the low-temperature molecular-beam epitaxy (MBE) of large-area monolayer α-In 2 Se 3 on graphene and demonstrate the use of α-In 2 Se 3 on graphene in ferroelectric Schottky diode junctions by employing high-work-function gold as the top electrode. The polarization-modulated Schottky barrier formed at the interface exhibits a giant electroresistance ratio of 3.9 × 10 6 with a readout current density of >12 A/cm 2 , which is more than 200% higher than the state-of-the-art technology. Our MBE growth method allows a high-quality ultrathin film of In 2 Se 3 to be heteroepitaxially grown on graphene, thereby simplifying the fabrication of high-performance 2D ferroelectric junctions for ferroresistive memory applications.

Published
2018
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31. Mo-Terminated Edge Reconstructions in Nanoporous Molybdenum Disulfide Film.

Author

Zhao X, Fu D, Ding Z, Zhang YY, Wan D, Tan SJR, Chen Z, Leng K, Dan J, Fu W, Geng D, Song P, Du Y, Venkatesan T, Pantelides ST, Pennycook SJ, Zhou W, and Loh KP

Abstract

The catalytic and magnetic properties of molybdenum disulfide (MoS 2 ) are significantly enhanced by the presence of edge sites. One way to obtain a high density of edge sites in a two-dimensional (2D) film is by introducing porosity. However, the large-scale bottom-up synthesis of a porous 2D MoS 2 film remains challenging and the correlation of growth conditions to the atomic structures of the edges is not well understood. Here, using molecular beam epitaxy, we prepare wafer-scale nanoporous MoS 2 films under conditions of high Mo flux and study their catalytic and magnetic properties. Atomic-resolution electron microscopy imaging of the pores reveals two new types of reconstructed Mo-terminated edges, namely, a distorted 1T (DT) edge and the Mo-Klein edge. Nanoporous MoS 2 films are magnetic up to 400 K, which is attributed to the presence of Mo-terminated edges with unpaired electrons, as confirmed by density functional theory calculation. The small hydrogen adsorption free energy at these Mo-terminated edges leads to excellent activity for the hydrogen evolution reaction.

Published
2018
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32. Band gap engineering and layer-by-layer mapping of selenium-doped molybdenum disulfide.

Author

Gong Y, Liu Z, Lupini AR, Shi G, Lin J, Najmaei S, Lin Z, Elías AL, Berkdemir A, You G, Terrones H, Terrones M, Vajtai R, Pantelides ST, Pennycook SJ, Lou J, Zhou W, and Ajayan PM

Abstract

Ternary two-dimensional dichalcogenide alloys exhibit compositionally modulated electronic structure, and hence, control of dopant concentration within each individual layer of these compounds provides a powerful tool to efficiently modify their physical and chemical properties. The main challenge arises when quantifying and locating the dopant atoms within each layer in order to better understand and fine-tune the desired properties. Here we report the synthesis of molybdenum disulfide substitutionally doped with a broad range of selenium concentrations, resulting in over 10% optical band gap modulations in atomic layers. Chemical analysis using Z-contrast imaging provides direct maps of the dopant atom distribution in individual MoS2 layers and hence a measure of the local optical band gaps. Furthermore, in a bilayer structure, the dopant distribution is imaged layer-by-layer. This work demonstrates that each layer in the bilayer system contains similar local Se concentrations, randomly distributed, providing new insights into the growth mechanism and alloying behavior in two-dimensional dichalcogenide atomic layers. The results show that growth of uniform, ternary, two-dimensional dichalcogenide alloy films with tunable electronic properties is feasible.

Published
2014
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