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Effects of resonant bonding and structural distortion during the phase change process in Sn2Sb2Se5

Abstract

The phase-change characteristics of Sn2Sb2Se5 (SSS), a pseudo-binary chalcogenide material, were investigated for use in phase-change random access memory applications. Although an analysis of the power and phase-change speed using laser static test equipment showed superior phase-change properties, several instabilities existed during the phase-change process. It was also found that the difference in resistivity between the crystalline and amorphous structure was high, as compared to conventional Ge2Sb2Te5 (GST). The SSS material also required a higher set/reset switching power than GST in electrical pulse switching tests. Based on extended X-ray absorption fine structure measurements and ab initio calculations of the charge distribution, short and long bonds were not found to co-exist around the Sn atoms, unlike the Ge atoms in GST. This evidence leads to enhanced resonant bonding in SSS, which prevents the Sn atoms from participating in the Ge-like phase-change mechanism. While the Ge atoms in crystalline GST tend to occupy defective octahedral sites, the Sn atoms in SSS prefer a tightly bonded resonant bonding state with a six-fold geometry. This strong resonant bonding results in a lack of Peierls-like distortion in the SSS structure. As a result, the competition between Peierls-like distortion and resonant bonding significantly affects the phase-change characteristics such as the SSS instability and switching process.

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Publication details

The article was received on 17 Mar 2017, accepted on 08 Jul 2017 and first published on 10 Jul 2017


Article type: Paper
DOI: 10.1039/C7TC01135K
Citation: J. Mater. Chem. C, 2017, Accepted Manuscript
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    Effects of resonant bonding and structural distortion during the phase change process in Sn2Sb2Se5

    M. Ahn, K. Jeong, S. Park, S. Park, H. Jung, J. H. Han, W. J. Yang, D. Kim, H. Jeong and M. Cho, J. Mater. Chem. C, 2017, Accepted Manuscript , DOI: 10.1039/C7TC01135K

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