An investigation of thin silver films on cleaved silicon surfaces

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Abstract
Vacuum-cleaved (111) silicon surfaces have been probed using LEED, AES and angle-resolved photoelectron spectroscopy. The experiments provide strong evidence for the validity of the Haneman model in describing the crystallography of the reconstructed cleaved face. The growth of silver overlayers ranging in thickness from a fraction (0.1) of a monolayer to several thousand AA was examined and the Stranski-Krastanov growth mechanism confirmed. On clean surfaces, silver shows (111) epitaxy with domains oriented parallel to the silicon substrate. The deposition of a single monolayer of silver atoms removes the silicon 2*1 reconstruction and the electronic nature of this silicon-silver monolayer interface is quite different from either that of the clean silicon or a thick silver film. The data show that the Schottky barrier formed between silicon and silver is already fully formed before the deposition of any silver, i.e. it has the same magnitude as the band bending at the clean surface. The implications of this result are discussed. In addition the adhesive nature of silver films on silicon has been probed. Interfacial failure is believed to be 'cohesive' rather than 'adhesive' in nature and occurs in the strained region between an adsorbed silver monolayer and the remainder of the silver film.