Tunnel Contacts for Spin Injection into Silicon: The Si-Co Interface with and without a MgO Tunnel Barrier—A Study by High-Resolution Rutherford Backscattering
Figure 2
Co on Si (100), low coverage (≤1.3 ML). Panels at the left-hand side: Co edge of HRBS spectra (circles) and RUMP simulations (solid lines). Panels at the right hand side: Co concentrations as determined by the RUMP simulations versus depth (depth scale: monolayers of Si, each at./cm2 thick). (a) Co deposition at RT. The peaks between 1800 and 1810 keV are due to backscattering from Co at the surface, the other peaks in the range of 1785–1800 keV due to Co atoms in the Si bulk (subsurface enrichment). (b) Co concentration profiles (Co/Si) in subsequent layers of the sample as obtained from (a) by RUMP simulations. Layer 0 is the topmost Si layer; −1, −2, −3, −4, and −5 are subsequent layers in the bulk. Note that the -axes for 0.08 and 1.19 ML have scales different from others. (c) Co deposition at −60°C. The peaks between 1800 and 1805 keV are due to backscattering from Co at the surface. The oscillations in the Co concentration mentioned in the text are clearly visible. (d) Co concentration (Co/Si) in the various Si (100) layers of the Si crystal as derived from (c) by RUMP simulations. Layer 1 (hatched column) corresponds to Co atoms on top of the Si crystal, layer 0 is the first Si layer, and layers −1, −2, −3, and −4 are subsequent layers in the Si bulk (solid columns).
