Epitaxial growth and structure characterization of single-crystal Co(11⦶20) films on Cr(100) surfaces

Abstract

Single-crystal Co films have been grown on two kinds of Cr(100) terminated surfaces on MgO(100) substrates by molecular beam epitaxy. The first was the growth of Co films on top of rough Cr(100) surfaces on MgO(100) substrate. hcp Co(11⦶20) films were prepared on such Cr(100) surfaces with about the same order of surface roughness as that of the Cr buffer layers. The second was the growth of high-quality and smooth Co(11⦶20) films on flat Cr(100) surfaces on Cr x Mo 1− x (100) graded buffer layers. We find that the use of Cr x Mo 1− x (100) graded buffer layers is critical to quickly prepare smooth and well-ordered Cr(100) surfaces. It is suggested that the symmetry breaking from four-fold Cr(100) to two-fold Co(11⦶20) may be due to the existence of surface steps under proper growth kinetics. The surface structure and crystal orientation of these films were characterized by reflection high-energy electron diffraction, atomic force microscopy and X-ray diffraction.