CAREER: Two-Dimensional Heterostructures Based On Transition Metal Dichalcogenides

University Of South Florida, Tampa FL

Investigators

Abstract

Nontechnical Description: Single layers of materials, also called 2-dimensional (2D) materials, are atomically thin materials that present an unusual combination of mechanical, optical and electronic properties; thus they are very attractive candidates for new-generation opto-electronic devices. Hetero-structures, i.e., stacking layers of different 2D materials, can be created to achieve new functionalities; by altering the local chemistry of a single layer, one can integrate different local properties in the hetero-structure. Although it is an essential step, the fabrication of such 2D hetero-structures still remains a technological challenge. The main goals of this project are to establish reliable methods and procedures to fabricate these complex 2D structures, and to acquire a clear understanding of the chemistry-structure-properties relationship by performing a comprehensive characterization of the heterostructures and related devices. The study is expected to impact future directions of 2D materials research through identifying and overcoming critical technical barriers, and facilitating the next generation, energy efficient, portable and flexible electronics. The project also includes genuine efforts oriented to raise the awareness of science among young students from underrepresented groups, and to motivate them for STEM disciplines. The research activities integrate with the educational plan, including involving undergraduate students early for research experiences, expanding the international collaborations with Mexico and Brazil, and increasing the participation of minority students in graduate studies. Technical Description: This project aims to advance the fundamental knowledge on the physical properties of two-dimensional crystals, e.g., atomically thin transition metal dichalcogenides with a higher degree of complexity, and their heterostructures. Innovative synthesis approaches, including multistep masking and thermal evaporation/deposition by alternating sources, and, lithographic and laser writing techniques in controlled environments, are used to create uniform and reproducible arrays of two-dimensional hetero-structures, both in-plane and vertically stacked. State-of-the-art optical, structural and electrical characterization techniques are applied to explore both the formation mechanisms of the hetero-junctions at the atomic level, and the effects of local chemistry and atomic arrangement on the overall physical properties of the heterostructures. In addition, the effects of doping and alloying on the optoelectronic properties, band gap tuning and electronic band alignment at the hetero-junctions, are also investigated. Furthermore, the project comprises the fabrication and testing of a variety of new optoelectronic devices such as photo-sensors, photovoltaics and light-emitting sources that use the two-dimensional hetero-structures as the active elements.