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 Au7Ga2on GaAs. For both GaAs orientations the epitaxial relationship (hkl)AU[hkl]Au/ (hkl)GaAs[hkl]GaAswas observed for all values of h, k and l. In addition, twin orientations were observed. For GaAs{111}, fourfold rotation twinning about the Au[l11] 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 Au7Ga2on GaAs{111} the epitaxial relationship was (111)Au/ (0110)Au7Ga2/(111)GaAsand 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 Au7Ga2and gold.