Effect of the Si substrate structure on the growth of two-dimensional thin Ag films

We investigated and compared the growth morphology of Ag films deposited on different Si surfaces at low temperatures and annealed at room temperature with scanning tunneling microscopy. Ag films on clean Si(1 1 1) 7×7 and Si(0 0 1) 2×1 surfaces exhibit with increasing film thickness: clusters (interconnected), islands with flat top terraces, flat films with voids extending down to the wetting layer, and flat films with no voids. The Ag films on Au-reconstructed Si(1 1 1) surfaces exhibit the same trend, with the exception that the initial islands exhibit no well defined heights. The growth morphology observed does not allow the identification of a single critical or minimum thickness of the Ag film as expected in the electronic growth model. Two different critical thicknesses are defined, which are higher for Si(0 0 1) 2×1 than for Si(1 1 1) 7×7 surfaces. The importance of surface states and pinning levels within the electronic growth model is discussed.