ABSTRACT: Phase change (PC) materials are a distinctive class of compounds that can be reversibly transformed between an amorphous and a crystalline state. The majority of optical data storage media utilizes PC materials that exhibit rapid, reversible amorphous à crystal phase transition with distinct opto-electronic properties which can be rationalized as (1) and off (0) computational binary states. Solid state materials with this property are relatively common but those exhibiting an amorphous à amorphous transition called polyamorphism are exceptionally rare. K2Sb8Se13 (KSS) reported here is the first example of a material that has both amorphous à amorphous polyamorphic transition and amorphous à crystal transition at easily-accessible temperatures (227°C and 263 °C, respectively). All three phases are stable in air at 25 °C and 1 atm. KSS exhibits three distinct optical bandgaps, Eg = 1.25, 1.0, and 0.74 eV for the amorphous-II, amorphous-I and crystalline versions, respectively. Room-temperature electrical conductivity of KSS increases by more than 2 orders of magnitude from amorphous-I to -II, and by another 2 orders of magnitude from amorphous-II to the crystalline state. This extraordinary behavior of KSS suggests that a new class of materials exists which could be a new source for multi-state PC materials to enable higher-order computing logic circuits, reconfigurable logic devices, and optical switches.

Polyamorphism induced multi-level electronic states in phase change K2Sb8Se13

255th National Meeting (2018)

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