Influence of interfacial hydrogen on Al thin film nucleation on Si

We use scanning tunneling microscopy to study the coverage-dependent effects of hydrogen on Al thin film nucleation on Si(100). Using a quench-and-look procedure we find that small amounts of H affect Al island structure. Specifically, Al films deposited onto Si having 0.15 monolayer of adsorbed monohydride show an increased island density and a preponderance of small (less than or equal to 4 atom) clusters, compared with growth on clean Si. We interpret this to be a result of reduced Al adatom diffusion lengths due to site blocking or trapping. Also, the effects of a full monolayer of hydrogen on Al thin film morphology are studied. Al deposited onto Si(100) terminated with a layer of monohydride forms three-dimensional islands, unlike growth on clean Si. Although a change in growth morphology is observed in thin Al films, the out-of-plane crystal texture of thick Al films (300-1000 Angstrom) is unaffected by a monolayer of interfacial hydrogen. Hydrogen is not present at a Si-Al interface after thick film growth at 100 degrees C on fully passivated substrates.