ROOM-TEMPERATURE DEPOSITION AND GROWTH OF AU ON CLEAN AND OXYGEN PASSIVATED SI(111) SURFACES INVESTIGATED BY OPTICAL 2ND-HARMONIC GENERATION

Room-temperature deposition and growth of Au on Si(111) is investigate d by means of optical second-harmonic generation. The process on the c lean 7 x 7 surface is compared under identical conditions to that of t he oxygen passivated surface. Ordered Au/Si interfaces occur in both c ases. For the 7 x 7 surface the interface ordering starts after deposi tion of 4 monolayers, completing the formation of a phase with some di ssolved Si, after which a continuous Au film grows between the substra te and the mixed phase. Oxygen passivation causes interface ordering f rom a lower Au coverage and a considerably higher degree of interface order. Oscillating second-harmonic generation intensities Versus cover age with periods in the 12-17 monolayer range show that quantum well s tates formed in the Au him are responsible for the second-harmonic sig nal. The annealing behaviours of the Au/Si structures are also studied , and discussed with the inclusion of photoemission results.