Non-Technical: Next generation electronics require advances in both materials and device designs. One promising direction is utilizing atomically thin materials because of their flexibility and high electron mobility. Graphene was the first such material identified in this new area of two-dimensional (2D) materials. Unfortunately, graphene is not a semiconductor, but a semimetal and is therefore not suitable for the digital logic circuits widely used today in electronics. Transition metal dichalcogenides are a family of 2D materials which share many of the promising aspects of graphene such as being atomically thin. In addition, they exhibit a wider variety of electronic and optoelectronic properties compared to graphene including many being semiconducting or metallic. This wide range of transition metal dichalcogenides allows one to select a material or a combination of materials best suited for a particular application. Indeed, by combining different 2D materials together in vertical heterostructures an even wider range of new device functionalities can be enabled. This collaborative research program will create new educational and research opportunities at both the University of Arizona, and the University of Texas at Austin. The program will strongly emphasize the training of graduate and undergraduate students from underserved groups, thus preparing them for industrial or academic careers. This workforce training, along with the expected research output, will boost the efforts to make our nation more competitive.
The goal of this collaborative research program is to study layered two-dimensional transition metal dichalcogenide materials and heterostructures for device applications, using a combination of controlled heterostructure fabrication techniques, scanning probe microscopy, and electrical transport measurements. Similar to graphene, the most widely studied two-dimensional material, transition metal dichalcogenides represent a larger class of layered materials with varying electronic properties, from semiconducting to superconducting. The diverse set of electronic properties in these materials makes them suitable for applications ranging from transistors to chemical sensors or photodetectors. Key to an understanding of their fundamental electronic properties is the role of the disorder potential, interfaces, and edges in individual layers, and of the band and rotational alignment in heterostructures. Specifically, the proposed effort will (1) measure band-alignment in transition metal dichalcogenide based heterostructures, (2) realize heterostructures of two-dimensional materials with controlled rotational alignment, (3) explore the impact of rotational alignment on the electronic properties of two-dimensional material heterostructures, and using these ingredients (4) design and fabricate novel heterostructure tunneling devices. This program builds on the PIs existing collaborative research and recent preliminary data on the fabrication and characterization of these heterostructures. The outcomes of this research program will include uncovering fundamental electronic properties of transition metal dichalcogenide-based heterostructures, new methods to create heterostructures, and novel devices for future electronics applications.
