The role of reductive and oxidative annealing processes in the phase composition and electrical conductivity of molybdenum oxides

摘要

The effect of reductive or oxidative annealings on pure MoO2 films was monitored by X-ray diffraction and four-probe electrical conductivity measurements. For partially oxidized samples, it was observed the expected conductivity decrease with respect to pristine MoO2, but reasonably high conductivity was measured as long as the samples showed a MoO2/MoO3 phase-mixture with relatively high MoO2 content. On the other hand, for completely oxidized (pure MoO3) samples, a very low conductivity, not measurable with the four-probe arrangement, was noticed. The results of these experiments, together with the observations of Raman chemical maps are discussed to shed some light on the origin of the electrical conductivity in MoOx. The occurrence of a MoO2/MoO3 composite was found to be crucial to obtain a conductive material. The results presented in this work are relevant for the use of MoOx as hole transport layer, transparent conductive oxide or other modern generation optoelectronic devices.