Influence of anisotropic Si(111)-(4 × 1)-In surface on growth of nanoscale In islands

Abstract

Reflectance anisotropy spectroscopy (RAS) and scanning tunneling microscopy (STM) are used to study the growth of indium (In) on the anisotropic Si(111)−(4 × 1)−In surface at room temperature. RAS shows that epitaxial growth of In is accompanied by the disappearance of the surface optical anisotropy at 1.9 eV which is the fingerprint for the (4 × 1)-In surface reconstruction and the appearance of a large minimum at 1.4 eV which is at the same energy as interband transitions observed on bulk crystalline In. Subsequent spectra taken on the surface, over 3 h, show that this minimum decreases and eventually disappears along with the reappearance of the original RAS signature of the (4 × 1)-In surface. STM of this surface shows elongated, anisotropic In crystal islands on top of a (4 × 1)-In reconstructed surface. Upon annealing the surface to 720 K, the surface reconstruction changes with STM showing regions covered with a phase that resembles the (√7 × √3)-In reconstruction and RAS showing a large positive anisotropy at about 1.5 eV. The epitaxial In islands now show a hexagonal shape, unlike on the (4 × 1) surface. Thus, the growth morphology of the islands is shown to be dependent on the initial surface reconstruction. The authors attribute these findings to Ostwald ripening of the In islands mediated by diffusion, which is dependent on the structurally different In wetting layers on the Si substrate.