Variations of Local Motifs around Ge Atoms in Amorphous GeTe Ultrathin Films

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• 作者：Ping Ma ; Hao Tong ; Ting Huang ; Ming Xu ; Niannian Yu ; Xiaomin Cheng ; Cheng-Jun Sun ; Xiangshui Miao
• 刊名：Journal of Physical Chemistry C
• 出版年：2017
• 出版时间：January 19, 2017
• 年：2017
• 卷：121
• 期：2
• 页码：1122-1128
• 全文大小：442K
• ISSN：1932-7455

文摘

Phase-change materials, the highly promising candidate for nonvolatile data recording, present a different phase-change property when film thickness shrinks to very deep submicron scale. The local structure of amorphous GeTe ultrathin films, which contributes to the characteristics of phase change, is examined using X-ray absorption measurements. Ge atoms are found to be low-coordinated when the film thickness decreases. Ge atoms are linked to neighbor atoms by covalent bond, and the weaker Ge–Te bonds are more easily broken, which suggests that Ge atoms are located in the defective Ge₂Te₃ local arrangement. The mixture of sp³/sp² hybridization and 3-coordinated Ge found in ab initio molecular dynamics simulations also supports this local motif. The exponential rise of crystallization temperatures of ultrathin films with decreasing film thickness, which is a vital parameter for phase change process, can be well explained by the proposed defective GeTe local arrangement.