MEDIUM-ENERGY ION-SCATTERING AND STM STUDIES ON CU/SI(111)

The structure of Cu on Si(111) 7 X 7 deposited at high temperature (300-600 degrees C) was examined by the results of medium energy ion scattering (MEIS) and scanning tunneling microscopy (STM). The structure of the Si bulk that is just under the incommensurate layer, which shows the ''5 X 5'' electron diffraction pattern, might be the double layer and the first layer of the Si bulk is deduced to be relaxed inward by 0.01 nm after the measurements and the Monte Carlo simulation of the blocking profiles of MEIS. The distance (0.05 nm) between the Cu and Si layer in the incommensurate layer was also estimated using the ultra high depth resolution capability (0.16 nm for Si) of MEIS. The Si structure in the incommensurate layer was deduced by the ratio of dark to bright areas of ''5 x 5'' after counting the number of Si atoms. The ratio was about 0.83 and there is about 1 ML of Si atoms in the incommensurate layer.