Anharmonicity of the vibrational modes of phase-change materials: A far-infrared, terahertz, and Raman study

Journal Article · 31 January 2018 · Vibrational Spectroscopy

DOI: https://doi.org/10.1016/j.vibspec.2018.01.005 · OSTI ID:1461623

Shportko, Konstantin ^[1]; Zalden, P. ^[2]; Lindenberg, A. M. ^[3]; Ruckamp, R. ^[4]; Gruninger, M. ^[4]

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1. National Academy of Sciences of Ukraine, Kyiv (Ukraine); RWTH Aachen Univ., Aachen (Germany)
2. SLAC National Accelerator Lab., Menlo Park, CA (United States); European XFEL GmbH, Schenefeld (Germany)
3. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States)
4. Univ. of Cologne, Cologne (Germany)

Phase-change materials are employed as active elements in optical and electronic memory devices. Upon crystallization, their visible and near-infrared dielectric properties change dramatically due to the formation of resonant bonds, a unique type of bond related to both metallic and covalent bonds. In this work we study the change of the anharmonicity upon crystallization as well as the impact of vacancy concentration and vacancy ordering on the anharmonicity. Our temperature-dependent study of vibrational modes directly reveals a correlation between anharmonicity, vacancy concentration, and ordering. Previously, such a correlation was derived only indirectly from measurements of the specific heat. Furthermore, the pronounced far-infrared contrast, even larger than the optical one, can enable the application of phase-change materials in photonic devices.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-76SF00515
• OSTI ID: 1461623
• Journal Information: Vibrational Spectroscopy, Vol. 95, Issue C; ISSN 0924-2031
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English