Effects of resonant bonding and structural distortion on the phase change properties of Sn2Sb2Se5. Issue 31 (24th July 2017)

• Record Type: Journal Article
• Authors: Ahn, Min; Jeong, Kwang-sik; Park, Seungjong; Park, Sungjin; Jung, Hoon; Han, Jeonghwa; Yang, Wonjun; Kim, Dasol; Jeong, Hongsik; Cho, Mann-Ho
• Is Part Of: Journal of materials chemistry. Volume 5:Issue 31(2017)
• Page Start: 7820
• Page End: 7829
• Publication Date: 2017-07-24
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c7tc01135k
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : The phase-change characteristics of Sn2 Sb2 Se5 (SSS), a pseudo-binary chalcogenide material, were investigated for use in phase-change random access memory applications. Abstract : The phase-change characteristics of Sn2 Sb2 Se5 (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 structures was high, as compared to conventional Ge2 Sb2 Te5 (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.