Temperature-depending growth and surface structures of low-coverage Al phases on Si(100) observed by scanning tunneling microscopy

Abstract The surface structures of Al on the Si(100) surface, at coverages less than one monolayer deposited at various temperatures, were studied by scanning tunneling microscopy (STM). Surface structures of 2 × 2 and 2 × 3 phases formed at temperatures below 350°C consist of Al-dimer lines with the dimerization parallel to that of the Si-dimers. From the STM images, we can find that a filled state of Al-Si backbonds and an empty state of Al-Al dimer bonds are observed prominently at about −3 and +1 eV at positions on the Si-dimer rows and between the Si-dimer rows, respectively. For deposition above 500°C, the Al-dimer lines change into molecular clusters, each one of them consisting of five or six Al atoms. These molecules form the c(4 × 2 n ) structure with buckling of underlying Si-dimer rows. At the same time, two-dimensional (2D) Si and Al islands with 2 × 1 and 2 × 2 structures were formed in the second layer on the c(4 × 2 n ) structure. The local structures of the low-coverage Al phases on Si(100), depending on the deposition temperature and coverage, are analyzed by STM.