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Unraveling the Atomic Structure of Bulk Binary Ga–Te Glasses with Surprising Nanotectonic Features for Phase-Change Memory Applications

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journal contribution
posted on 2021-07-28, 12:07 authored by Maria Bokova, Andrey Tverjanovich, Chris J. Benmore, Daniele Fontanari, Anton Sokolov, Maxim Khomenko, Mohammad Kassem, Ilya Ozheredov, Eugene Bychkov
Binary Ge–Te and ternary Ge–Sb–Te systems belong to flagship phase-change materials (PCMs) and are used in nonvolatile memory applications and neuromorphic computing. The working temperatures of these PCMs are limited by low-T glass transition and crystallization phenomena. Promising high-T PCMs may include gallium tellurides; however, the atomic structure and transformation processes for amorphous Ga–Te binaries are simply missing. Using high-energy X-ray diffraction and Raman spectroscopy supported by first-principles simulations, we elucidate the short- and intermediate-range order in bulk glassy GaxTe1–x, 0.17 ≤ x ≤ 0.25, following their thermal, electric, and optical properties, revealing a semiconductor–metal transition above melting. We also show that a phase change in binary Ga–Te is characterized by a very unusual nanotectonic compression with the high internal transition pressure reaching 4–8 GPa, which appears to be beneficial for PCM applications increasing optical and electrical contrast between the SET and RESET states and decreasing power consumption.