The growth of Ag films on Si(100)

Room temperature condensation of Ag films on Si(100) in the submonolayer and monolayer range has been studied by means of voltage-dependent scanning tunneling microscopy and in some cases by scanning tunneling spectroscopy (STM). The uncovered Si(100) substrate showed various kinds of local atomic structures, which influence the growth behavior of the Ag films. Short heating of Si(100) produced a 2×1 reconstruction with a comparably small number of defects. Extensive heating increased the number of defects and finally led to ordering of defects and formation of a 2×8 reconstruction showing weak 1/8 and strong 1/2 order low-energy electron diffraction (LEED) beams. In the submonolayer range Ag condenses in row-like structures along the dimer rows of the substrate (i.e., vertical to the dimer direction). The Ag atoms are repelled from the Si defect sites. For a large number of defects (e.g., for a 2×8 reconstructed substrate) 1 ML Ag does not cover completely the substrate surface but already starts with the growth of three-dimensional Ag islands. The Stranski–Krastanov growth mode of the system Ag/Si (100) (interface+island formation) has therefore been convincingly established. The interaction between the Ag atoms in the interface layer and the Si substrate is remarkably weak. We reproducibly observed current instabilities near Ag sites and distinct diffusion processes of the Ag atoms during the STM measurements.