Physics and Astronomy Colloquium - Dr. Zhixian Zhou, Wayne State University
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Title: Two-Dimensional Layered Semiconductors beyond Graphene: Electronics and Device Physics
Abstract: The successful isolation of two-dimensional (2D) graphene has stimulated research on a broad range of other 2D materials, among which layered transition metal dichalcogenides (TMDs) have attracted particular attention. The semiconducting members of the TMD family including MoS2, MoSe2 and WSe2 have not only demonstrated many of the "graphene like" properties desirable for electronic applications such as a relatively high mobility, mechanical flexibility, chemical and thermal stability, and the absence of dangling bonds, but also have a substantial band gap (1 ~ 2 eV depending on the material and its thickness), which is absent in 2D graphene but required for mainstream logic applications. However, a major bottleneck in electronic applications of TMDs is their tendency to form a substantial Schottky barrier with most electrode metals, which severely limits their performance. In this talk, I will discuss our recent work aiming to overcome this fundamental challenge and subsequently explore the intrinsic transport properties of TMDs.1-5 1. Perera, M. M.; Lin, M.-W.; Chuang, H.-J.; Chamlagain, B. P.; Wang, C.; Tan, X.; Cheng, M. M.-C.; Tománek, D.; Zhou, Z. Improved Carrier Mobility in Few-Layer MoS2 Field-Effect Transistors with Ionic-Liquid Gating. ACS Nano 2013, 7, 4449-4458. 2. Chuang, H.-J.; Tan, X.; Ghimire, N. J.; Perera, M. M.; Chamlagain, B.; Cheng, M. M.-C.; Yan, J.; Mandrus, D.; Tománek, D.; Zhou, Z. High Mobility WSe2 p- and n-Type Field-Effect Transistors Contacted by Highly Doped Graphene for Low-Resistance Contacts. Nano Letters 2014, 14, 3594-3601. 3. Chuang, H.-J.; Chamlagain, B.; Koehler, M.; Perera, M. M.; Yan, J.; Mandrus, D.; Tománek, D.; Zhou, Z. Low-Resistance 2D/2D Ohmic Contacts: A Universal Approach to High-Performance WSe2, MoS2, and MoSe2 Transistors. Nano Letters 2016, 16, 1896-1902. 4. Guan, J.; Chuang, H.-J.; Zhou, Z.; Tománek, D. Optimizing Charge Injection across Transition Metal Dichalcogenide Heterojunctions: Theory and Experiment. ACS Nano 2017. 5. Andrews, K.; Bowman, A.; Rijal, U.; Chen, P.-Y.; Zhou, Z. Improved Contacts and Device Performance in MoS2 Transistors Using a 2D Semiconductor Interlayer. ACS Nano 2020, 14, 6232-6241.
Bio: Dr. Zhixian Zhou received his PhD from Florida State University/National High Magnetic Field Laboratory in 2004. After working at the Oak Ridge National Laboratory as a postdoctoral research associate, he joined Wayne State University as an assistant professor in 2007 and was promoted to associate professor with tenure in 2013.