MICROSTRUCTURAL EVOLUTION DURING EPITAXIAL-GROWTH OF AG ON VICINAL INP(100) SURFACES

The initial stages of epitaxial growth of Ag on InP(100) have been stu died using in situ and ex situ electron microscopy. Vicinal InP substr ates were cleaned by heating to about 406 degrees C in ultrahigh vacuu m. Silver was deposited at substrate temperatures between 350 and 500 degrees C. The microstructural evolution was monitored for coverage be tween 0.5 and 8 monolayers using in situ high spatial resolution secon dary electron microscopy and ex situ plan-view transmission electron m icroscopy (TEM). At sub-monolayer coverage, uniform, faceted islands o f Ag are formed with edges aligned along InP [110] directions. Continu ed deposition leads to growth of preexisting islands followed by coale scence. During coalescence, a reduction in the island height, an incre ase in island-substrate interfacial area, and a disappearance of facet ing are observed. At high coverage, during high temperature (450 degre es C) growth, the formation of faceted pits are observed. For higher t emperatures (500 degrees C) and at low coverage, islands transform fro m square to rectangular shapes. Plan-view TEM indicates that the small est Ag islands (similar to 5 nm) are not coherent with the substrate a nd that there are two distinct epitaxial relationships between the Ag islands and the InP substrate. For high-temperature growth, the (11O) Ag plane is parallel to InP(100) substrate and there is evidence for c hemical reaction and presence of In on the surface. For lower temperat ure depositions (350-400 degrees C), the (100)Ag is parallel to (100) InP. (C) 1996 American Institute of Physics.