Synthesis and electrical properties of cubic $Na_{x}WO_{3}$ thin films across the metal-insulator transition

Abstract

Highly oriented (1 0 0) $Na_{x}WO_{3}$ thin films were fabricated in the composition range 0.1 \leq x \leq 0.46 by pulsed laser deposition technique. The films showed transition from metallic to insulating behaviour at a critical composition between x = 0.15 and 0.2. The pseudo-cubic symmetry of $Na_{x}WO_{3}$ thin films across the transition regionis desirable for understanding the composition controlled metal-insulator transition in the absence of any structural phase transformation. The electrical transport properties exhibited by these films across the transition regime were investigated. While the resistivity varied as T-2 at low temperatures in the metallic regime, avariable range hopping conduction was observed for the insulating samples. For metallic compositions, a non-linear dependence of resistivity in temperature was also observed from 300 to 7 K, whose exponent varied with the composition of the film