Epitaxial growth of cobalt oxide by atomic layer deposition

Highly oriented thin films of cobalt oxide were made by the atomic layer deposition (ALD) technique, using Co(thd) 2 (Hthd=2,2,6,6-tetramethylheptan-3,5-dione) and ozone as precursors. Films were deposited on single-crystalline substrates of MgO(1 0 0), α-Al 2O 3(0 0 1), and SrTiO 3(1 0 0). Epitaxial growth has been established with the following orientations: (0 0 1)[1 0 0]Co 3O 4∥(0 0 1)[1 0 0]MgO, (1 1 1)[1 1 1]Co 3O 4∥(0 0 1)[0 0 1]α-Al 2O 3, and (0 0 1)[1 0 0]Co 3O 4∥(0 0 1)[1 0 0]SrTiO 3. The resulting texture was studied as function of deposition temperature in the range 138–283 °C for MgO(1 0 0) and 186–283 °C for the remaining substrates. The topography and morphology of the films were investigated by atomic force microscopy (AFM), and in selected cases scanning electron microscopy. The specific electronic resistivities of as-deposited films grown on the various substrates were measured to be from 0.8 to 85 Ωcm.