Evolution of a preferred orientation of polycrystalline grains in obliquely deposited gold films on an amorphous substrate

By measuring the azimuthal dependence of the optical second-harmonic response from gold films that are obliquely deposited on fused silica, we study the evolution of the film texture as a function of the film thickness. As the latter increases from 10 to 30 nm, we observe that the symmetry of the optical second-harmonic generation (SHG) changes from having only a mirror plane that coincides with the incidence plane of the deposition to having a three-fold rotation axis in addition to the mirror plane. When combined with the x-ray diffraction measurements, the nonlinear optical measurement shows that (1) the polycrystalline grains in the obliquely deposited gold films are terminated mainly with (111) facet planes; (2) at the film thickness of 30 nm, the terminating facet planes are tilted away from the substrate normal by a few degrees towards the deposition flux and have a preferred in-plane orientation such that one of the [110] axes in the terminating facet plane is perpendicular to the incidence plane of the deposition.