Research Center for Advanced Measurement and Characterization, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
London Centre for Nanotechnology, University College London, 17-19 Gordon St., London WC1H 0AH, United Kingdom.
J Phys Condens Matter. 2023 Feb 10;35(13). doi: 10.1088/1361-648X/acb628.
The electronic properties of the surface of-FeSihave been debated for a long. We studied the surface states of-FeSifilms grown on Si(001) substrates using scanning tunnelling microscopy (STM) and spectroscopy (STS), with the aid of density functional theory calculations. STM simulations using the surface model proposed by Romanyuk(2014B155305) reproduce the detailed features of experimental STM images. The result of STS showed metallic surface states in accordance with theoretical predictions. The Fermi level was pinned by a surface state that appeared in the bulk band gap of the-FeSifilm, irrespective of the polarity of the substrate. We also observed negative differential conductance at ∼0.45 eV above the Fermi level in STS measurements performed at 4.5 K, reflecting the presence of an energy gap in the unoccupied surface states of-FeSi.
-FeSi 表面的电子特性长期以来一直存在争议。我们使用扫描隧道显微镜 (STM) 和光谱学 (STS) 研究了在 Si(001) 衬底上生长的-FeSi 薄膜的表面态，并辅以密度泛函理论计算。使用 Romanyuk（2014B155305）提出的表面模型进行的 STM 模拟再现了实验 STM 图像的详细特征。STS 的结果显示表面态具有金属性，这与理论预测一致。费米能级被表面态钉扎，该表面态出现在-FeSi 薄膜的体能带隙中，与衬底的极性无关。我们还在 4.5 K 下进行的 STS 测量中观察到费米能级上方约 0.45 eV 处的负微分电导，这反映了-FeSi 未占据表面态中存在能隙。
