Growth behavior and electronic structure of cobalt islands on Ag/Ge(111) surface

[[abstract]] By Scanning Tunneling Microscopic (STM) we can understand the growth behavior of cobalt islands on Ag/Ge(111)- (4×4) and (√ 3×√ 3) surface at high temperature (400 ℃) . With the increase of cobalt coverage, the exposure area of (4×4) decrease more apparently then √ 3×√ 3 does. Besides the stronger binding at the interface of cobalt and (4×4), nucleation of Cobalt Island on the (4×4) interface may result silver atoms to move to other (4×4) and (3×1) area and form more area of (√ 3×√ 3). In order to reduce the total surface free energy, small islands combine with large island that is Ostwald ripening. After high-temperature (400 ℃) evaporation on the Ag/Ge(111)- √3×√3, the cobalt atom has sufficient kinetic energy to find the most stable position, and heat treatment allow cobalt islands to form terrace. By STS we could find local density of states (LDOS) at the step edge and terrace are different, and find that the filled state of cobalt islands show different features at step edge and terrace. In the Ag/Ge(111) surface will form two kinds of reconstruction cobalt island, one was √ 13 × √ 13 reconstruction of cobalt islands, and the other was 2 × 2 reconstruction of cobalt islands. √13×√ 13 cobalt islands have different LDOS on (4×4) and (√3×√3) due to interface effect. When 2 × 2 cobalt island are of 7~8 layers height, the LDOS of cobalt islands are different from the 2×2 reconstruction low coverage sample.