Boundary-structure determination of Ag/Si(111) interfaces by x-ray diffraction

Different Ag/Si(111) systems have been examined using synchrotron x-ray diffraction. Multi-atomic-layer deposition of Ag onto a Si(111)-(7×{}7) surface maintained at room temperature results in an unstrained, (111)-oriented film. The interface shows a Ag-modified (7×{}7) structure which when annealed above 200--250 ^∘{}C transforms to a (1×{}1) structure. Although this is near the characteristic temperature for formation of the ({}3 ×{} {}3 )R30^∘{} surface reconstruction commonly observed for a monolayer of Ag adsorbed on Si(111), no evidence of this ({}3 ×{} {}3 )R30^∘{} reconstruction was found at the interface. A Ag monolayer ({}3 ×{} {}3) R30^∘{} surface, further covered by multilayer Ag deposition at room temperature, also shows no indication of the ({}3 ×{} {}3) R30^∘{} reconstruction at the interface. This indicates that the actual interface structure may or may not be related to the clean or adsorbed layer structures. The structure of the Ag-Si interface was further characterized by scans of the crystal truncation rods. Both the (7×{}7) interface prepared by room-temperature deposition and the annealed (1×{}1) interface show fairly sharp boundaries. The results suggest some intermixing occurs at the monolayer level for the annealed interface. The structure of the Ag film was also investigated.