Cr(110) texture induced by epitaxy on Al2O3(0001) substrates: Preferential grain growth in the 〈001〉 direction

Chromium exhibits (110) textured growth on Al2O3(0001) substrates induced by epitaxy. Epitaxy occurs in nine distinct orientations, leading to a polycrystalline film of grains with (110) out-of-plane orientation but different in-plane orientations. For e-beam evaporated films, scanning electron microscopy shows acicular Cr grains elongated in the 〈001〉 direction. Grain boundaries occur along (11¯0) and (1¯10) planes, which is explained by the low surface energy of {110} planes in the bcc structure. The direction of the long axes of the grains relative to the substrate is defined by the underlying hexagonal symmetry of the substrate, leading to a unique tri-directional microstructure.