TY - JOUR

T1 - Atypical phase-change alloy Ga 2Te 3

T2 - Atomic structure, incipient nanotectonic nuclei, and multilevel writing

AU - Tverjanovich, Andrey

AU - Khomenko, Maxim

AU - Benmore, Chris J.

AU - Bereznev, Sergei

AU - Sokolov, Anton

AU - Fontanari, Daniele

AU - Kiselev, Aleksei

AU - Lotin , Andrey

AU - Bychkov, Eugene

N1 - Publisher Copyright: © The Royal Society of Chemistry.

PY - 2021/12/21

Y1 - 2021/12/21

N2 - Emerging brain-inspired computing, including artificial optical synapses, photonic tensor cores, neuromorphic networks, etc., needs phase-change materials (PCMs) of the next generation with lower energy consumption and a wider temperature range for reliable long-term operation. Gallium tellurides with higher melting and crystallization temperatures appear to be promising candidates and enable achieving the necessary requirements. Using high energy X-ray diffraction and Raman spectroscopy supported by first-principles simulations, we show that vitreous g-Ga2Te3 films essentially have a tetrahedral local structure and sp3 hybridization, similar to those in the stable fcc Ga2Te3 polymorph and in contrast to a vast majority of typical PCMs. Nevertheless, optical pump-probe laser experiments revealed high-contrast, fast and reversible multilevel SET-RESET transitions raising a question related to the phase change mechanism. A recently observed nanotectonic compression in bulk glassy Ga-Te alloys seems to be responsible for the PCM performance. Incipient nanotectonic nuclei, reminiscent of monoclinic high-pressure HP-Te II and rhombohedral HP-Ga2Te3, are present as minorities (2-4%) in g-Ga2Te3 but are suggested to grow dramatically with increasing temperature while interacting with appropriate laser pulses. This leads to co-crystallization of HP-polymorphs amplified by a high internal local pressure reaching 4-8 GPa. The metallic HP-forms provide an increasing optical and electrical contrast, favorable for reliable PCM operations, and higher energy efficiency. This journal is

AB - Emerging brain-inspired computing, including artificial optical synapses, photonic tensor cores, neuromorphic networks, etc., needs phase-change materials (PCMs) of the next generation with lower energy consumption and a wider temperature range for reliable long-term operation. Gallium tellurides with higher melting and crystallization temperatures appear to be promising candidates and enable achieving the necessary requirements. Using high energy X-ray diffraction and Raman spectroscopy supported by first-principles simulations, we show that vitreous g-Ga2Te3 films essentially have a tetrahedral local structure and sp3 hybridization, similar to those in the stable fcc Ga2Te3 polymorph and in contrast to a vast majority of typical PCMs. Nevertheless, optical pump-probe laser experiments revealed high-contrast, fast and reversible multilevel SET-RESET transitions raising a question related to the phase change mechanism. A recently observed nanotectonic compression in bulk glassy Ga-Te alloys seems to be responsible for the PCM performance. Incipient nanotectonic nuclei, reminiscent of monoclinic high-pressure HP-Te II and rhombohedral HP-Ga2Te3, are present as minorities (2-4%) in g-Ga2Te3 but are suggested to grow dramatically with increasing temperature while interacting with appropriate laser pulses. This leads to co-crystallization of HP-polymorphs amplified by a high internal local pressure reaching 4-8 GPa. The metallic HP-forms provide an increasing optical and electrical contrast, favorable for reliable PCM operations, and higher energy efficiency. This journal is

KW - DYNAMICS

KW - GLASSES

KW - HIGH-PRESSURE PHASE

KW - LOCAL-STRUCTURE

KW - NEUTRON-DIFFRACTION

KW - OPTICAL-PROPERTIES

KW - RAMAN-SPECTROSCOPY

KW - TE

KW - THIN-FILMS

KW - X-RAY

UR - https://www.researchgate.net/publication/355927282_Atypical_phase-change_alloy_Ga2Te3_atomic_structure_incipient_nanotectonic_nuclei_multilevel_writing

UR - http://www.scopus.com/inward/record.url?scp=85121144503&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/3b4b332d-d48c-3312-9ff2-42de63e72652/

U2 - 10.1039/D1TC03850H

DO - 10.1039/D1TC03850H

M3 - Article

VL - 9

SP - 17019

EP - 17032

JO - Journal of Materials Chemistry C

JF - Journal of Materials Chemistry C

SN - 2050-7526

IS - 47

ER -