Materials World Network: Understanding and exploiting mixed, ultra-fast optical electrical behavior in nanoscale phase change materials

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The objective of this proposal is to comprehensively investigate the material properties of chacogenides (both binary and ternary compounds) in mixed optical-electrical phase transitions. The underlying principle of memory storage in Ge-Sb-Te alloys is reversible crystalline to amorphous phase transitions that are associated with significant changes in optical reflectivity and electrical resistivity. However, although the optical and electrical mechanisms have been independently investigated, there is no work done on the mixed-mode operation, i.e. switching the material optically while probing it electrically and vice-versa. This is however extremely important for a host of potentially game-changing applications ranging from optically gated ultra-fast transistors to non-von-Neumann arithmetic processing. Our collaborative research will focus on investigating fundamental phase switching properties in mixed-mode, elucidating phase change mechanisms via dynamic optical probing of electrical phase transitions, and exploring the materials best suited for unconventional future arithmetic processors. To accomplish these challenging objectives, the following approach will be undertaken:1. The development of pulsed laser deposition (PLD) growth technique to synthesize complex ternary phase change nanowires with excellent control over chemical composition and diameters; followed by their structural, chemical and electrical characterization.2. The study phase-change dynamics by mixed-mode time-resolved femtosecond optical and ultrafast electrical measurements of phase switching behavior, and the dependence of such behavior on the chemical composition and size of the phase-change nanowires.3. A detailed study of the size-dependency of mixed-mode operation in phase change materials via a dedicated nano-photonics test bed