MgB2超导薄膜的变温拉曼光谱研究  

Study on Raman Spectra of MgB Superconducting Film at Different Temperatures

作　　者：李艳丽[1] 伍岳 张新月 孔祥东[1,2] 高召顺 韩立[1,2] LI Yan-li;WU Yue;ZHANG Xin-yue;KONG Xiang-dong;GAO Zhao-shun;HAN Li(Institute of Electrical Engineering,Chinese Academy of Sciences,Beijing 100190,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院电工研究所,北京100190 [2]中国科学院大学,北京100049

出　　处：《光谱学与光谱分析》2021年第11期3451-3455,共5页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(U1831202)资助。

摘　　要：MgB2作为迄今为止超导转变温度最高的合金超导体,由于其具有结构简单、相干长度长、晶界间不存在弱连接、上临界场很高、电-声散射时间短等特点,MgB2超导薄膜在电子学领域有着广阔的的应用前景。拉曼光谱是研究电-声子相互作用和超导能带的一种有效方法,且已广泛用于分析MgB2材料的电子、声子特征以及超导体能带结构,研究表明,样品质量、晶粒尺寸以及测试条件对MgB2拉曼峰的峰位和峰形影响很大,其中拉曼光谱随温度的变化也是一个研究重点,但目前关于MgB2变温拉曼光谱的研究,测试的温度范围相对较小,局限在83 K到室温区域或是转变温度附近。研究了大范围温度区间内MgB2薄膜的拉曼光谱变化,采用混合物理化学沉积法在(0001)SiC衬底上制备了MgB2多晶薄膜,薄膜的晶粒尺寸约为300 nm,超导转变温度为39.3 K,对其在10~293 K之间的拉曼光谱进行了测试,测量的波数范围为20~1 200 cm-1。变温拉曼光谱的测试结果显示,在高频620 cm-1附近以及低频80和110 cm-1附近存在MgB2的拉曼峰。经分析,低频区域出现的两个拉曼峰的频率与超导能隙宽度相对应,表明MgB2的双能隙特性。考虑到MgB2中四种声子模式的拉曼活性,高频620 cm-1附近的拉曼峰应是由E2g振动模所贡献的,且随着测试温度的降低,该拉曼峰的峰位未发生明显的偏移,但半高宽显著变小,从293 K时的380.7 cm-1减小到10 K时的155.7 cm-1,分析表明E2g声子与电子系统的非线性耦合所引起的非简谐效应可能是拉曼峰半高宽线性变小的主要原因。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 E2 g 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

关 键 词：MGB2 薄膜 变温 拉曼光谱 

分 类 号：O433.4[机械工程—光学工程]