Texture of MBE grown Cr films on α-Al₂O₃(0001): The occurrence of Nishiyama-Wassermann (NW) and Kurdjumov-Sachs (KS) related orientation relationships

The orientation and texture of Cr(110) films on the basal plane of α-Al₂O₃ was investigated by transmission electron microscopy. The Cr was deposited via molecular beam epitaxy at a substrate temperature of 110°C resulting in the formation of crystallites with columnar mophology. Two orientation relationships (OR) were observed between Cr(110) and α- Al₂O₃(0001): Cr[001] // α-Al₂ O₃[̄110] and Cr[̄111] // α-Al₂ O₃[̄110]. Each of these orientation relationships exhibited two variants which were rotated ±5.26° around the substrate normal. The orientation relationships can be rationalized on the basis of geometry, rotational symmetry and lattice mismatches of the Cr/(110) /α-Al₂O₃(0001) interface. The occurrence of all OR can be related to Nishiyama-Wassermann (NW) and Kurdjumov-Sachs (KS) orientations and are discussed with respect to previous experimental results and geometrical parameters of other bcc metals which were grown on α-Al₂O₃(0001).