EAGER: Understanding Photochemical 2H-1T Phase Transition in Monolayer MoS2

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Non-technical Description: Ultra-thin transition metal dichalcogenides (TMDs) materials are promising candidates for flexible, low-power and transparent electronics and optoelectronics. Manipulating the atomic arrangements, referred to as crystal phases, can transform TMDs from semiconducting to metallic materials, which is a promising way to improve the overall device performance and/or to attain new functionalities. The current phase-engineering methods either rely on expensive and hostile chemicals or are incompatible with large-scale manufacturing. This project aims to develop a novel photochemical approach, which is controllable, scalable, low-cost, environmentally benign and compatible with electronic device fabrication, to induce phase-change in molybdenum disulfide. The research advances the state of knowledge of the phase-change mechanisms in TMD materials and explores the potential of TMD materials for applications in wearable electronics, foldable displays and lightings, and advanced integrated medical devices. The research effort is integrated with education and outreach activities, including training students in TMD materials, organizing a summer science camp and research internship programs for high school students that are traditionally underrepresented in the STEM field.Technical Description: This project proposes a novel photochemical concept for phase transition in monolayer molybdenum disulfide to address the pressing need for performance improvement in 2D-TMD based electronic/optoelectronic devices. The goal of this EAGER project is to understand photochemically induced 2H to 1T phase transformation in monolayer molybdenum disulfide and to establish processing-structure and structure-property correlations. In pursuit of this goal, the project objectives are to (1) validate the phase change mechanism through systematic characterizations of photo-chemically formed hetero-phase molybdenum disulfide and evaluate the controllability of the transition by varying processing parameters; (2) investigate the stabilization mechanism of the metastable metallic phase for improved device reliability; and (3) evaluate intriguing optical and electrical properties of phase-engineered molybdenum disulfide. Combined approaches of advanced structural characterization, optical analysis, device fabrication and electrical measurements are used in this research to gain fundamental understandings of the phase-change mechanism and the phase-engineered 2D-TMD materials.