| AVS 63rd International Symposium & Exhibition | |
| 2D Materials Focus Topic | Tuesday Sessions |
| Session 2D-TuA |
| Session: | Novel Quantum Phenomena in 2D Materials |
| Presenter: | Lee Walsh, University of Texas at Dallas |
| Authors: | L.A. Walsh, University of Texas at Dallas R. Yue, University of Texas at Dallas A.T. Barton, University of Texas at Dallas H. Zhu, University of Texas at Dallas L. Cheng, University of Texas at Dallas R. Addou, University of Texas at Dallas J. Hsu, University of Texas at Dallas J. Kim, University of Texas at Dallas M. Kim, University of Texas at Dallas L. Colombo, Texas Instruments R.M. Wallace, University of Texas at Dallas C.L. Hinkle, University of Texas at Dallas |
| Correspondent: | Click to Email |
Transition metal dichalcogenides (TMDs) are 2D materials which belong to a class known as van der Waals materials where the adjacent layers are held together by weak van der Waal’s interactions and, in principle, have no surface dangling bonds, which permits a relaxed growth requirement in terms of lattice matching. This relaxed lattice-matching criteria allows us to couple these materials based primarily on their band alignment and electronic properties. WTe2 is a TMD with an equilibrium structure in the distorted octahedral (1T’) phase. This 1T’ phase of WTe2 is a semi-metal and hence may be implemented as a 2D metal in an all-2D heterostructure for new devices. Monolayer 1T’ WTe2 has been separately predicted to be a Weyl semi-metal and to behave as a relatively wide bandgap (>0.1 eV) topological insulator, possessing helical edge states which have a number of interesting properties including time reversal symmetry, spin-momentum locking, and ballistic transport1,2. The trigonal prismatic (2H) phase of WTe2 is viewed as an integral part of the tunnel field effect transistor (TFET) device due to its bandgap and effective mass and has been theoretically predicted to provide low power operation and sub 60 mV subthreshold swing. WTe2 is truly a remarkable material with intriguing electronic properties owing to its strong spin-orbit coupling and layered crystal structure.
In this work, we demonstrate the first report of WTe2 growth by molecular beam epitaxy (MBE) on a variety of substrate materials (Bi2Te3, MoS2, and graphite). We will discuss the optimal MBE growth conditions (substrate temperature, flux rates etc.) along with in-depth structural and chemical characterization of the resultant single crystal thin films. Characterization was conducted via reflection high energy electron diffraction, transmission electron microscopy, scanning tunneling microscopy/spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Challenges associated with Te incorporation and simple device and transport measurements will be presented.
This work is supported in part by the Center for Low Energy Systems Technology (LEAST), one of six centers supported by the STARnet phase of the Focus Center Research Program (FCRP), a Semiconductor Research Corporation program sponsored by MARCO and DARPA. It is also supported by the SWAN Center, a SRC center sponsored by the Nanoelectronics Research Initiative and NIST. This work was also supported in part by the Texas Higher Education Coordinating Board’s Norman Hackerman Advanced Research Program.
1. A. A. Soluyanov et. al, Nature527, 495 (2015).
2. X. Qian et. al, Science346, 1344 (2014).