Electric field driven abnormal increase in conductivity of tungsten-doped VO2 nanofilms

Abstract

Ion doping is an effective way in tuning the metal-insulator transition (MIT) and physical properties of vanadium dioxide (VO2). However, the mechanism of ion doping effect is not quite clear up to now. The first principle calculations in our last paper indicated that W dopants injected localized d-electrons in rutile VO2 (VO2(R)). Herein, we prepared a group of V1-xWxO2 (0 ≤ x ≤ 2.7%) films, and applied external electric field to drive the MIT transition of W-doped VO2. The variation of electrical conductivity of W-doped VO2 was investigated with different W concentrations and applied voltages. Without external electric field, the conductivity of W-doped VO2(R) is lower than that of undoped VO2(R), and decreases with increasing the W concentration. Upon loading electric field, the conductivity of W-doped VO2(R) is increased by applied voltages and reaches a saturation value which is higher than that of undoped VO2(R) and increases with the W concentration, while the conductivity of undoped VO2(R) is independent of applied voltage. The experimental results suggest external electric field drives the excitation of the localized d electrons injected by W dopants. This work presents useful information for understanding the ion doping effect in VO2, and demonstrates the existence of conduction multiplets in W-doped VO2, proposing potential application of W-doped VO2 in multi-field effect devices such as for high-density storage.