THE INITIAL GROWTH OF AG FILMS ON W(110) - A HELIUM DIFFRACTION STUDY

Growth of Ag films on W(110) has been monitored for substrate temperatures between 170 and 800 K. In agreement with earlier studies we find that two epitaxial layers are formed which are stable up to the desorption temperature. We have determined the buckling amplitude of these incommensurate structures and find that they are less than expected from a hard-sphere model using a uniformly distorted (111) plane for the Ag film. We conclude that local rearrangements must take place in the film. In comparison with Cu growth, we find that the monolayer is less well ordered although the defect density is no more than 8% at 1.0 ML No stable layer by layer growth occurs for coverages above the bilayer. Layer by layer growth does not occur at 170 K where diffusion is too slow to allow the necessary material transport.