( Invited ) Phase-Change 2D Materials for Advanced Electronics

Layered van der Waals 2D materials, such as transition metal dichalcogenides (TMDs), are promising platforms for next-generation electronic and memory technologies. In particular, externally driven structural phase transitions in TMDs offer a route to dynamically tune their electrical and optical properties, enabling the development of ultra-thin, energy-efficient, and non-volatile memories and logic devices. This talk focuses on controlled growth and reversible phase transitions in molybdenum ditelluride (MoTe₂) single crystals, with the aim of exploring such applications. We employ chemical vapor transport (CVT) to grow MoTe₂ single crystals in well-defined crystal structures: a semiconducting 2H phase with controllable n- and p-type doping, and a semimetallic 1T′ phase. The formation of these 2H and 1T′ polytypes, as well as reversible 2H–1T′ transformations, is achieved by tuning the growth temperature profile and post-growth annealing conditions. We further modulate the 2H–1T′ phase boundary by alloying MoTe₂ with tungsten (W) to form Mo₁₋ₓWₓTe₂ solid solutions. The resulting understanding of the structure–phase–property relationships in 2H and 1T′ MoTe₂ enables the fabrication of resistive random-access memory (RRAM) cells and lateral homojunction field-effect transistors (FETs) that exploit the controllable semiconductor-to-metal transition for device functionality.