BOUNDARY-STRUCTURE DETERMINATION OF AG SI(111) INTERFACES BY X-RAY-DIFFRACTION/

Different Ag/Si(111) systems have been examined using synchrotron x-ra y diffraction. Multi-atomic-layer deposition of Ag onto a Si(111)-(7X7 ) surface maintained at room temperature results in an unstrained, (11 1)-oriented film. The interface shows a Ag-modified (7X7) structure wh ich when annealed above 200-250 degrees C transforms to a(1X1) structu re. Although this is near the characteristic temperature for formation of the (root (3) over bar X root (3) over bar)R30 degrees surface rec onstruction commonly observed for a monolayer of Ag adsorbed on Si(111 ), no evidence of this (root (3) over bar X root (3) over bar)R30 degr ees reconstruction was found at the interface, A Ag monolayer (root (3 ) over bar X root (3) over bar)R30 degrees surface, further covered by multilayer Ag deposition at room temperature, also shows no indicatio n of the (root (3) over bar X root (3) over bar)R30 degrees reconstruc tion at the interface. This indicates that the actual interface struct ure may or may not be related to the clean or adsorbed layer structure s. The structure of the Ag-Si interface was further characterized by s cans of the crystal truncation rods. Both the (7X7) interface prepared by room-temperature deposition and the annealed (1X1) interface show fairly sharp boundaries. The results suggest some intermixing occurs a t the monolayer level for the annealed interface. The structure of the Ag film was also investigated.