X-ray diffraction (pole figure) study of the epitaxy of gold thin films on GaAs

Abstract

X-ray diffraction (pole figure) measurements were made on gold thin films (300–2300 Å) evaporated on GaAs{111} and GaAs{001} to investigate the heteroepitaxy and twinning of the gold films and the chemoepitaxy of Au7Ga2 on GaAs. For both GaAs orientations the epitaxial relatiobship (hkl)Au[hkl]Au// (hkl)GaAs[hkl]GaAs was observed for all values of h, k and l. In addition, twin orientations were observed. For GaAs{111}, fourfold rotation twinning about the Au[111] direction resulted in four azimuthal orientations: [112]Au // [112]GaAs, [112]Au // [112]GaAs, [112]Au // [110]GaAs and [112]Au // [110]GaAs. For GaAs{001}, reflection twinning with the four Au{111} planes as twinning planes resulted in four other orientations with Au(001) at approximately 71° from GaAs(001). The relative amounts of the twins depended on the substrate temperature, the film thickness and the deposition rate. Chemoepitaxy was observed for Au7Ga2 on GaAs{111}; the epitaxial relationship was (111)Au / (0110)Au7Ga2 // (111)GaAs, and Au7Ga2[0001] was off by 10° from GaAs[110], toward GaAs[011], i.e. Au7Ga2[0001] was off by 10° from Au[110], toward Au[011]. This relationship corresponds to a perfect lattice match between Au7Ga2 and gold.