Study on Raman Spectra of MgB2 Superconducting Film at Different Temperatures
LI Yan-li1, WU Yue1, ZHANG Xin-yue1, 2, KONG Xiang-dong1, 2*, GAO Zhao-shun1, 2, HAN Li1, 2
1. Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
Abstract：MgB2 superconducting film, as the alloy superconductor with the highest superconducting transition temperature so far, has a broad application prospect in the field of electronics because of its simple structure, long coherent length, no weak connection between grain boundaries, high upper critical field, short electron-phonon scattering time and so on. Raman spectroscopy is an effective method to study the electron-phonon interaction and superconducting band. Moreover, Raman spectroscopy has been used to study the electron-phonon characteristics and superconducting band structure of MgB2. Research shows that sample quality, grain size and test conditions greatly influence the peak position and shape of the Raman peak of MgB2. The change of Raman spectrum with temperature is also a research priority. However, the temperature range of MgB2 variable temperature Raman spectrum is relatively small, which is limited to 83 K to room temperature or the region near the transition temperature. In this work, the Raman spectra of MgB2 film in a large temperature range are studied. The polycrystalline MgB2 film was prepared on (0001) SiC substrate via hybrid physical-chemical vapor deposition with grain size ~300 nm and superconducting transition temperature 39.3 K. The Raman spectra of MgB2, from 20 to 1 200 cm-1, were measured and studied in the temperature region from 10 to 293 K. The Raman spectra show that Raman peaks related to MgB2 appear at ~620 cm-1 in high-frequency region and at ~80 and ~110 cm-1 in low-frequency region. The frequency of the two Raman peaks in the low-frequency region corresponds to the width of the superconducting energy gap, indicating the dual-gap characteristics of MgB2. Considering the Raman activity of the four phonon modes in MgB2, the Raman peak at ~620 cm-1 in high-frequency region is contributed by the E2g vibration mode. And as temperature decreases, no obvious peak position shift is observed. Nevertheless, the FWHM of the Raman peak decreases with temperature. Furthermore, the FWHM is 380.7 cm-1 at 293 K, and 155.7 cm-1 at 10 K. Analysis shows that the non-harmonic effect caused by the nonlinear coupling between E2g phonon and electronic system may be the main reason for the linear decrease of the FWHM.
Key words：MgB2; Film; Different temperature; Raman spectra
李艳丽，伍 岳，张新月，孔祥东，高召顺，韩 立. MgB2超导薄膜的变温拉曼光谱研究[J]. 光谱学与光谱分析, 2021, 41(11): 3451-3455.
LI Yan-li, WU Yue, ZHANG Xin-yue, KONG Xiang-dong, GAO Zhao-shun, HAN Li. Study on Raman Spectra of MgB2 Superconducting Film at Different Temperatures. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2021, 41(11): 3451-3455.
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