Morphology of the Au-Si interface formed during solidification of liquid Au/Si(111) islands

Au islands grown on Si(111) substrates at substrate temperatures of 500 and 600 degrees C, both of which are greater than the bulk Au-Si eutectic temperature of 363 degrees C, are characterized using atomic force (AFM) and electron microscopy. Specific islands are imaged using AFM before and after Au dissolution using aqua regia to characterize the Au-Si interface formed as the islands solidify from the liquid phase while cooling from the growth temperature. Subsequent to Au dissolution, the islands present a craterlike morphology with a pit that may extend below the substrate surface depending on growth and annealing conditions. Craters formed beneath islands grown at a substrate temperature of 600 degrees C exhibit pits that penetrate below the substrate surface to a depth that is proportional to the area of the island footprint and possess a well-developed (111) facet at their base. Facets are also sometimes observed in the crater sidewalls and are more prevalent in samples slowly cooled through the solidus temperature than those that are radiatively quenched. Transmission electron micrographs of etched islands indicate the presence of segregated Au nanocrystals entrained in the crater lip. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3661996]