Preparation of hcp-Ni epitaxial films on Cr underlayers

Abstract

Ni epitaxial films are prepared by ultra-high vacuum rf magnetron sputtering on Cr underlayers of (100) and (211) planes grown hetero-epitaxially on MgO substrates of (100) and (110) orientations, respectively. The film growth behavior and the crystallographic properties are studied by in-situ reflection high energy electron diffraction and pole figure X-ray diffraction. Metastable hcp-Ni(1120) and hcp-Ni(1100) crystals respectively nucleate on Cr(100) and Cr(211) underlayers, where the hcp crystals are stabilized through hetero-epitaxial growth. With increasing the film thickness, the hcp structure in the Ni films starts to transform into more stable fcc structure by atomic displacement parallel to the hcp(0001) closed packed plane. The resulting films consist of hcp and fcc crystals.