报告题目：2D/2D Junctions as Low-resistance Contacts for 2D Layered Semiconductors beyond Graphene
报告人：Zhixian Zhou，Department of Physics and Astronomy, Wayne State University, USA
报告时间：2017年4月26日（星期三）上午9:30
报告地点：新能源材料与创新研究院215会议室
报告简介：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.1-4 Particularly, we have used heavily doped graphene and 2D semiconductors to fabricate low-resistance ohmic contacts for a variety of TMDs.
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.
报告人简介：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 for nearly three years, he joined Wayne State University as a tenure-track assistant professor of physics in August 2007 and was promoted to associate professor with tenure in August 2013. Dr. Zhou’s research has been centered on investigating the electrical transport properties, device physics and applications of nanoscale materials including graphene and two-dimensional (2D) layered semiconductors (such as MoS2, WSe2, MoSe2 and black phosphorus). Particularly, he was among the first to recognize that the initially reported low carrier-mobility in MoS2–based transistors was an artifact of high Schottky barrier at the contacts. He innovatively applied ionic liquid and graphene to overcome this challenge. More recently, Dr. Zhou’s group developed a new strategy that utilizes 2D/2D vertical junctions to engineer low-resistance ohmic contacts, which turn TMDs including WSe2, MoS2 and MoSe2 into high-performance transistors. His work along this direction resulted in multiple highly cited publications in high-impact journals such as Nano Letters and ACS Nano. Dr. Zhou has also been recognized by invitations to present his research at international scientific conferences and workshops as an invited speaker, including a prestigious invited talk at the 2016 Gordon Conference on Two Dimensional Electronics beyond Graphene. Dr. Zhou’s research on graphene and 2D materials beyond graphene has been supported by 2 major research grants from the National Science Foundation (NSF) of the United States with Dr. Zhou as the sole PI. He is also the recipient of a number of awards including College of Liberal Arts and Science's Excellence in Teaching Award (2010), Career Development Chair Award (2016-2017), and Sultana N. Nahar Prize for Distinction in Research in Physics and Astronomy (2017). During the past 5 years, Dr. Zhou has authored over 20 peer reviewed publications, most of which were published in high-impact journals with Dr. Zhou as the corresponding author.