Electron Transport in Single Crystals of Niobium Dioxide

Abstract

We have made measurements of the Hall effect and resistivity as well as of thermoelectric power in the temperature range 300–450 K. The results of these measurements are interpreted in terms of a small polaron model of conduction. Additionally, our resistivity and thermoelectric power measurements were extended to 1200 K in an attempt to elucidate the nature of the transition in conductivity occurring in the range 1071–1103 K. For the c direction, this transition appears to be from a semiconducting to a metallic state and a possible explanation for this is given in terms of a lattice distortion model.

Reproducible resistance switching characteristics of pulsed laserdeposited polycrystalline Nb2O5

“…The switching mechanism might be regarded as a semiconductor-tometallic transition and filamentary conduction. This view is supported by the conduction path that forms as a result of the cooperative rearrangement of the Nb ions within the NbO x and by the conduction mechanism of ohmic behavior characteristics observed in the set state [15][16][17].…”

Band gap of epitaxial in-plane-dimerized single-phase NbO2films

“…[25][26][27] The strong conductivity change occurs along the dimerization direction (rutile c-axis). 28 For devices utilizing NbO 2 as a channel material (in-plane transport) such as transistors, one would like the dimerization direction to be in the plane of the film. Prior reports of NbO 2 thin film growth all show polycrystalline material with or without preferred orientation.…”

Growth of NbO2 by Molecular-Beam Epitaxy and Characterization of its Metal-Insulator Transition

“…Resistivity measurements were taken every 25 K while heating. The results of these measurements, alongside published single crystal data [4], are shown in Fig. 3(b), where partial pressures of molecular oxygen during growth are noted.…”

“…This oxidation occurs because Nb 2 O 5 is the thermodynamically stable phase in 1 atm of air. Previous research on NbO 2 at high temperature did not encounter this as those measurements were taken in either a vacuum or hydrogen ambient [4]. To prolong film oxidation, the electrical resistivity measurements presented here were taken by surrounding the measurement apparatus with a large plastic bag full of flowing nitrogen gas.…”

“…1(a) [4]. As temperature increases from 400 K to 1100 K, the electrical resistivity of NbO 2 changes by more than three orders of magnitude.…”