Characterization of cobalt films grown on MgO(001) by dc-biased-sputter deposition

Cobalt films (90 nm thick) were deposited on MgO(001) substrates at 250 degrees C by de-sputtering at 2.5 kV in pure argon gas. A bias voltage V-s between 0 and -180 V was applied to the substrate during the deposition. Reflection high-energy electron diffraction, cross-sectional transmission electron microscopy (XTEM) and X-ray photo electron spectroscopy, as well as measurements of the temperature coefficient of resistivity and saturation magnetization (4 pi M(s)), all as a function of V-s, confirmed that the structural and physical properties of cobalt films are most improved at - V-s = 140 V with a Co(001)parallel to MgO(001) and Co[010]parallel to MgO[010] relationship. A structural study of cobalt films prepared at - V-s = 140 V by high-resolution XTEM revealed that the stress induced in cobalt films is relaxed by the generation of defects such as misfit dislocations, lattice expansion and partial lattice distortions.