Optical and IR studies on r.f. magnetron sputtered ultra-thin MoO3 films

Ultra-thin MoO3 films were deposited onto glass and Si substrates by r.f. magnetron sputtering. The optical and IR properties of the films were studied in the range of 250 to 1000 nm and 400 to 1500 cm-1, respectively. The optical transmission spectra show a significant shift in absorption edge. The energy gap of the films deposited at 373 K and 0.1 mbar was found to be 3.93 eV, and it decreases with increasing substrate temperature and decreasing sputtering pressure. The IR transmittance spectra shows strong modes of vibrations of Mo=O and Mo-O-Mo units of MoO3 molecule. A significant change in energy gap and a shift in frequency of IR modes were observed in ultra-thin MoO3 films. (orig.)