A simple model of epitaxial growth

A discrete solid-on-solid model of epitaxial growth is introduced which, in a simple manner, takes into account the effect of an Ehrlich-Schwoebel barrier at step edges as well as the local relaxation of incoming particles. Furthermore a fast step edge diffusion is included in 2+1 dimensions. The model exhibits the formation of pyramid-like structures with a well-defined constant inclination angle. Two regimes can be distinguished clearly: in an initial phase (I) a definite slope is selected while the number of pyramids remains unchanged. Then a coarsening process (II) is observed which decreases the number of islands according to a power law in time. Simulations support self-affine scaling of the growing surface in both regimes. The roughness exponent is alpha =1 in all cases. For growth in 1+1 dimensions we obtain dynamic exponents z = 2 (I) and z = 3 (II). Simulations for d=2+1 seem to be consistent with z= 2 (I) and z= 2.3 (II) respectively.Comment: 8 pages Latex2e, 4 Postscript figures included, uses packages a4wide,epsfig,psfig,amsfonts,latexsy

INFRARED SPECTROSCOPY OF PHYSISORBED MOLECULES ON ALKALI HALIDE SURFACES

Author Institution: Department of Chemistry, Indiana UniversityVaporization of alkali halides has been used to produce high surface area films which are transparent in the $infrared.^{1}$ Small molecules adsorbed on such surfaces in sub-monolayer coverages have been studied by infrared spectroscopy to characterize surface-adsorbate and/or adsorbate-adsorbate $interactions^{2}$. We have observed coverage-dependent absorptions due to CO on 77K NaCl films, with features attributed to multiple sites at the surface. Other adsorbed molecules studied in our laboratory will also be discussed. 1. M. Folman and Y. Kozirovski, J. Coll. Interf. Sci 38, 51 (1972) and reference contained therein. 2. J. Heidberg, S. Zehme, C.F. Chen, and H. Hertmann, Ber. Buns. Ges. Phys. Chem. 15, 1046 (1971)