Materials Research Bulletin, Vol.40, No.9, 1443-1450, 2005
Synthesis and electrical properties of cubic NaxWO3 thin films across the metal-insulator transition
Highly oriented (1 0 0) NaxWO3 thin films were fabricated in the composition range 0.1 <= x <= 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 NaxWO3 thin films across the transition region is 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, a variable 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. (C) 2005 Elsevier Ltd. All rights reserved.