Atomic layer deposition and characterization of vanadium oxide thin films

In this study, VOx films were grown by atomic layer deposition (ALD) using V(NEtMe)(4) as the vanadium precursor and either ozone or water as the oxygen source. V(NEtMe)(4) is liquid at room temperature and shows good evaporation properties. The growth was investigated at deposition temperatures from as low as 75 degrees C, up to 250 degrees C. When using water as the oxygen source, a region of constant growth rate (ca. 0.8 angstrom/cycle) was observed between 125 and 200 degrees C, with the ozone process the growth rate was significantly lower (0.31-0.34 angstrom/cycle). The effect of the process conditions and post-deposition annealing on the film structure was investigated. By varying the atmosphere under which the films were annealed, it was possible to preferably form either VO2 or V2O5. Atomic force microscopy revealed that the films were smooth (rms < 0.5 nm) and uniform. The composition and stoichiometry of the films were determined by X-ray photoelectron spectroscopy. Conformal deposition was achieved in demanding high aspect ratio structure.