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

Abstract

Au islands grown on Si(111) substrates at substrate temperatures of 500 and 600 °C, both of which are greater than the bulk Au-Si eutectic temperature of 363 °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 °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.

Au impact on GaAs epitaxial growth on GaAs (111)B substrates in molecular beam epitaxy

“…9,10 Different metal nanoparticles, such as Au, 11 Fe, 12 Pt, 13 Pd, 14 and Ga 15 have been used to catalyst nanowire growth. 16 Among all kinds of metallic catalysts, Au has been commonly used to catalyze the growth of semiconductor nanowires 9,17 and nanowire heterostructures. [18][19][20] There are several approaches to prepare Au catalysts, such as aerosolgenerated Au particles, 21 colloidal Au particles, 22,23 electron beam lithography defined Au particles, 24 and Au particles generated by annealing of thin films.…”

Catalyst–substrate interaction and growth delay in vapor–liquid–solid nanowire growth

“…Such shapes are reminiscent of etch pits in crystalline germanium, bound by {111} planes which etch as the slowest ones [33]. Studies of the interface between eutectic AuSi melt and solid Si show that it is formed by {111}-oriented planes as well [34,35]. Hence, it is plausible to conclude that during annealing the catalytic nanoparticles dissolve the substrate beneath (if possible), thus reaching the corresponding eutectic composition at given temperature.…”

Guided VLS Growth of Epitaxial Lateral Si Nanowires

“…Thus, we believe that lateral NWs have the same growth rates and that the broad length distribution reflects a distribution of growth times. This distribution of growth times could result from a delay in growth of lateral NWs caused by the craters that form beneath the thermally deposited Au seeds. , Figure S3 displays AFM images of these craters, which show that there are crater rims that extend above the substrate surface that may impede growth for some lateral NWs. As shown, the crater rims extend for different heights above the substrate surface, and this height can vary around the perimeter of the rim.…”