Multistates and Polyamorphism in Phase-Change K₂Sb₈Se₁₃


The phase-change (PC) materials in the majority of optical data storage media in use today exhibit a fast, reversible crystal → amorphous phase transition that allows them to be switched between on (1) and off (0) binary states. Solid-state inorganic materials with this property are relatively common, but those exhibiting an amorphous → amorphous transition called polyamorphism are exceptionally rare. K2Sb8Se13 (KSS) reported here is the first example of a material that has both amorphous → amorphous polyamorphic transition and amorphous → crystal transition at easily accessible temperatures (227 and 263 °C, respectively). The transitions are associated with the atomic coordinative preferences of the atoms, and all three states of K2Sb8Se13 are stable in air at 25 °C and 1 atm. All three states of K2Sb8Se13 exhibit distinct optical bandgaps, Eg = 1.25, 1.0, and 0.74 eV, for the amorphous-II, amorphous-I, and crystalline versions, respectively. The room-temperature electrical conductivity 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 suggests that a new class of materials exist which could provide multistate level systems to enable higher-order computing logic circuits, reconfigurable logic devices, and optical switches.



Research Center/Lab(s)

Center for High Performance Computing Research


SMI, LP, LZ, DDB, VDP, MG, TJM, MGK, MJB, RL and JEM acknowledge support from the MRSEC program (NSF DMR-1720139) at the Materials Research Center.

Keywords and Phrases

Antimony compounds; Computation theory; Computer circuits; Crystalline materials; Digital storage; Logic devices; Optical data storage; Optical switches; Phase change materials; Reconfigurable hardware; Selenium compounds, Amorphous-amorphous transition; Crystal phase transition; Crystal transition; Electrical conductivity; Orders of magnitude; Polyamorphic transitions; Reconfigurable logic; Solid-state materials, Amorphous materials, article; crystal; electric conductivity; logic; room temperature

International Standard Serial Number (ISSN)

0002-7863; 1520-5126

Document Type

Article - Journal

Document Version


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© 2018 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Jul 2018