Preparation of cobalt oxide films by plasma-enhanced metalorganic chemical vapour deposition

Co oxide films were prepared on glass substrates at 150-400 degrees C by plasma-enhanced metalorganic chemical vapour deposition using cobalt (II) acetylacetonate as a source material. NaCl-type CoO films were formed at low O-2 flow rate of 7cm(3) min(-1) and at a substrate temperature of 150-400 degrees C. The CoO films possessed (100) orientation, independent of substrate temperature. Deposition rates of the CoO films were 40-47 nm min(-1). The CoO film deposited at 400 degrees C was composed of closely packed columnar grains and average diameter size at film surface was 60 nm. At high O-2 flow rate of 20-50 cm(3) min(-1), high crystalline spinel-type Co3O4 films were formed at a substrate temperature of 150-400 degrees C. The Co3O4 film deposited at 400 degrees C possessed (100) preferred orientation and the film deposited at 150 degrees C possessed (111) preferred orientation. Deposition rates of the Co3O4 films were 20-41 nm min(-1). Both Co3O4 films with (100) and (111) orientation had columnar structure. The shape and average size of the columnar grains at the film surface were different; a square shape and 35 nm for (100)-oriented Co3O4 film and a hexagonal shape and 60 nm for (111)-oriented film, respectively.