Resistivity of Single Crystal Molybdenum Dioxide
The chemical vapour transport method was used to grow molybdenum oxide single crystals so that their electrical properties could be analyzed. Satisfactory single crystal samples of MoO2 and Mo4O11 were grown successfully using I2 as a transport agent. Crystal growths using TeCl4 as a transport agent were also performed, though with mixed results. This approach yielded MoO2, MoO3, and Mo9O26, but this produced samples of a quality not suitable for single crystal analysis. Measurements performed on these samples yielded unique results, due to their mixed oxide nature, but as the composition of each sample was inconsistent, even between crystals from the same growth, little can be said about them definitively. Rubidium doped single crystal growths were also attempted, to build on previous polycrystalline Rb doped sample research, however no growths successfully included measurable amounts of Rb. While resistivity and heat capacity measurements performed on MoO2 did identify a phase transition in the area of 267K reported by other researchers, there was however no evidence found to support a reported 220K electronic transition . In Mo4O11 two previously identified 109K and 30K charge density wave transitions were observed in the DC resistivity. When AC resistivity measurements were performed the 30K transition was not apparent. Instead, a divergence of the cooling and warming curves not seen in the DC experiments occurred above 200K, with previously unseen peaks appearing at 285K and 250K when cooling from 400K.