Si衬底上生长的铁硅化合物结构和取向分析

采用分子束外延法分别在650-920 ℃的Si（110）和920 ℃的Si（111）衬底表面生长出铁的硅化物纳米结构，并主要分析了920 ℃高温下纳米结构的形貌、组成相及其与Si 衬底的取向关系. 扫描隧道显微镜（STM）研究表明，920 ℃高温下，Si（110）衬底上生长的铁硅化合物完全以纳米线的形式存在，且其尺寸远大于650 ℃低温下外延生长的纳米线尺寸；Si（111）衬底上生长出三维岛和薄膜两种形貌的铁硅化合物，其中三维岛具有金属特性且直径约300 nm、高约155 nm，薄膜厚度约2 nm. 电子背散射衍射研究表明920 ℃高温下Si（110）衬底上生长的纳米线仅以β-FeSi₂的形式存在，且β-FeSi₂相与衬底之间存在唯一的取向关系：β-FeSi₂（101）//Si（111）；β-FeSi₂ 010]//Si110]；Si（111）衬底上生长的三维岛由六方晶系的Fe₂Si 相组成，Fe₂Si 属于164 空间群，晶胞常数为a=0.405 nm，c=0.509 nm；与衬底之间的取向关系为Fe₂Si（001）∥Si（111）和Fe₂Si120]//Si112].

Structure and Orientation Analysis of Iron Silicide Epitaxially Grown on Si Substrates

Iron silicides were grown on Si(110) and Si(111) substrates by the molecular beam epitaxy method at 650-920 ℃ and 920 ℃, respectively. Scanning tunneling microscopy observation showed that only nanowires (NWs) formed on Si(110), and the dimensions of the NWs increased with increasing growth temperature. The sizes of the NWs grown at 920 ℃ reached ~80 nm high, ~250 nm wide, and several μm long, and were much larger than NWs grown at 650 ℃, indicating that high temperature was favorable for NW growth. Electron backscatter diffraction characterization identified that the crystal structure of the NWs grown at 920 ℃ was β-FeSi₂ with a single orientation of β-FeSi₂(101)//Si(111)), β-FeSi₂010]//Si110]. Iron silicides grown on Si(111) at 920 ℃ formed three-dimensional (3D) islands and ultra-thin films. The 3D islands were identified as the Fe₂Si phase with hexagonal crystal structure and space group 164, and the cell constants at room temperature were a=0.405 nm and c=0.509 nm. The orientation relationship between the Fe₂Si phase and the Si(111) substrate was Fe₂Si(001)//Si(111), Fe₂Si120]//Si112].