Preferred crystal orientation of cobalt ferrite thin films induced by ion bombardment during deposition

Abstract

Thin films of Co_xFe_3−xO_4−y (x=0.8, 1.0, 1.15, 1.25, 1.5, 1.8) were prepared under 100–500 eV Ar⁺‐ion bombardment during film deposition. Strong crystallization enhancement and preferred crystallographic orientation were observed as the effects of ion bombardment. Crystal orientation normal to the substrate depended on the composition x; 〈110〉‐axis orientation was obtained for x=0.8 and 1.0 and 〈111〉 orientation for x=1.15, 1.25, 1.5, and 1.8. The orientation was not affected significantly by the incident angle of the ions and did not vary with ion energy in the range 100–500 eV. The mechanism of crystal orientation is thought to have a close relationship with the preferential sputtering of oxygen by Ar⁺‐ion impact.