Growth of Ni Thin Films on Al2O3 Single-Crystal Substrates

Ni thin films were prepared on Al2O3(1120) and Al2O3(0001) single-crystal substrates by ultrahigh vacuum molecular beam epitaxy (UHV-MBE). The film growth structure and the magnetic properties were investigated. Ni epitaxial thin films with Ni(111) and Ni(100) planes parallel to the substrate surface are obtained on Al2O3(1120) substrates, whereas Ni polycrystalline films grow on Al2O3(0001) substrates. The Ni(111) film formed on Al2O3(1120) substrate consists of two types of domains whose orientations are rotated around the film normal by 30° each other. The magnetic properties of Ni films grown on Al2O3 substrates are influenced by the magnetocrystalline anisotropy and the shape anisotropy caused by the roughness of Ni islands which form the Ni thin films. The relationships between the film structure and the magnetic properties are discussed.