Strong carrier localization in 3d transition metal oxynitride LaVO3-xNx epitaxial thin films

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 5; no. 7; pp. 1798 - 1802
• Main Authors: Sano, M, Hirose, Y, Nakao, S, Hasegawa, T
• Format: Journal Article
• Language: English
• Published: 2017
• Subjects: Carriers; Doping; Grain boundaries; Insulators; Localization; Mathematical models; Position (location); Thin films
• DOI: 10.1039/c6tc04160d
• ISSN: 2050-7526

Perovskite LaVO3 is a typical Mott insulator that exhibits insulator to metal transition by hole doping via substitution of an alkali earth element for La (La1-xSrxVO3 or La1-xCaxVO3). In this study, we investigated the electrical transport properties of its anion-substituted counterpart, LaVO3-xNx (0 less than or equal to x less than or equal to 0.71). LaVO3-xNx epitaxial thin films with high crystallinities and smooth surfaces were grown by plasma-assisted pulsed laser deposition. The electrical resistivity ( rho ) of the thin films was remarkably lower than previously reported values for bulk polycrystals of LaVO3-xNx, indicating a suppressed contribution of the resistive grain boundaries to rho in the present films. Plots of rho against temperature for the LaVO3-xNx thin films showed that they were insulating (d rho /dT < 0) even at the highest doping level (x = 0.71), which is much larger than the threshold values for insulator to metal transition in La1-xSrxVO3 (x = 0.18) and La1-xCaxVO3 (x = 0.3). The curves of rho against temperature were well described using the Efros-Shklovskii-like variable range hopping model, suggesting that random potential introduced by N substitution in the VX6 conduction path induces strong carrier localization in LaVO3-xNx.