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

Co oxide films were prepared on glass substrates at 150-400°C by plasma-enhanced metalorganic chemical vapour deposition using cobalt (II) acetylacetonate as a source material. NaCl-type CoO films were formed at low O2 flow rate of 7 cm3 min-1 and at a substrate temperature of 150-400°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°C was composed of closely packed columnar grains and average diameter size at film surface was 60 nm. At high O2 flow rate of 20-50 cm3 min-1, high crystalline spinel-type Co3O4 films were formed at a substrate temperature of 150-400°C. The Co3O4 film deposited at 400°C possessed (100) preferred orientation and the film deposited at 150°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.