Non-reactive dc magnetron sputter deposition of Mo-O thin films from ceramic MoOx targets

The present work investigates the microstructure-property relations of Mo-O thin films synthesised by non-reactive dc magnetron sputter deposition from ceramic MoOx targets with compositions ranging from x = 2.5 to 2.8. Two series of films with different deposition powers, 150 and 450 W, were synthesised. The O content in the films is ~ 10% lower than in the target due to element-specific scattering of the sputtered species during the transport from the target to the substrate. The evolution of microstructure and chemical bonds was studied by X-ray photoelectron spectroscopy, X-ray diffraction and Raman spectroscopy. The structure of the films is dominated by the thermodynamically stable phases MoO2 and MoO3, as well as the intermediate phases Mo4O11 and Mo9O26. The films exhibit high absorbance of up to 75% and reflectance below 12% with electrical resistivity values in the range of 10− 2 to 1 Ωcm. In general, the use of oxide targets in dc magnetron sputter deposition of Mo-O films offers an efficient and reliable alternative to films sputtered reactively from metal targets and might thus enable their use in a wide range of opto-electronic applications.