Wu Qiang, Altman M S
Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China.
Ultramicroscopy. 2015 Dec;159 Pt 3:530-5. doi: 10.1016/j.ultramic.2015.02.006. Epub 2015 Feb 18.
The quantum size effect (QSE) in electron reflectivity from Fe thin films grown on a W(110) surface precovered with a two monolayer Cu film has been investigated using spin polarized low energy electron microscopy. Spin-dependent QSE-induced oscillations in the reflected intensity occur with energy and film thickness. The series of intensity peaks that is observed identifies spin-dependent quantum well resonances in the Fe film that are sensitive to electronic band structure and details of the buried interface. Information about the spin-dependent unoccupied bands of the Fe film in the ΓΝ direction normal to the film plane is obtained by analyzing the observed quantum well resonance conditions. The spin-split bands that are determined are uniformly shifted downward by 1.7 eV compared to bulk-like bands determined previously in Fe films on a bare W(110) substrate by the same method. Evidence is also obtained that the buried interface that defines the thin film quantum well boundary is located one layer above the W(110) surface. These results suggest that the Cu layer in direct contact with the substrate remains largely intact, but the weakly-bound second Cu layer mixes or segregates freely.
利用自旋极化低能电子显微镜研究了在预覆盖有两层铜膜的W(110)表面上生长的铁薄膜的电子反射率中的量子尺寸效应(QSE)。反射强度中与自旋相关的QSE诱导振荡随能量和薄膜厚度而发生。观察到的一系列强度峰确定了铁薄膜中与自旋相关的量子阱共振，这些共振对电子能带结构和掩埋界面的细节敏感。通过分析观察到的量子阱共振条件，获得了关于铁薄膜在垂直于薄膜平面的ΓΝ方向上与自旋相关的未占据能带的信息。与之前用相同方法在裸W(110)衬底上的铁薄膜中确定的类体带相比，确定的自旋分裂带均匀地下移了1.7 eV。还获得了证据表明，定义薄膜量子阱边界的掩埋界面位于W(110)表面上方一层处。这些结果表明，与衬底直接接触的铜层基本保持完整，但弱结合的第二层铜层自由混合或分离。
