Tuning the Structural and Optoelectronic Properties of Sub-stoichiometric Molybdenum Trioxide (MoOx, x < 3) Thin Films through the Oxygen Flow During the Reactive Magnetron Sputtering Deposition

We report on the optoelectronic and structural properties of MoO3-x thin layers deposited by reactive DC magnetron sputtering, of a pure Mo target under different oxygen to total flow ratios [r(O2) = O2/Ar, ranging from 0.25% to 16%]. Structural, morphological, optical and electronic transport analyses were systematically carried out on the deposited films. Transmission electron analysis showed that the films are compact and amorphous for low r(O2) and porous and crystalline for high O-content (i.e. 8 and 16 %). The associated hole mobilities were found to vary by almost two orders of magnitudes with respect to r(O2), and reached the very high value of ~20 cm2/Vs for 0.08 of oxygen. Correlations between optical transmittance/absorbance, oxidation states, different refractive indexes and the oxygen content are also presented and discussed.