Temperature dependence of the electrical conductivity of dry lithiated Tungsten trioxide thin films

Abstract

A great deal of basic and applied research has been dedicated in the past couple of decades to the transition metal oxide (TMO) thin films such as those of tungsten trioxide (WO3). This is due to the interesting reversible optical and electrical switching that occurs in these materials under various external influences. These switching properties are interesting both from the physics point of view as well as for their application. In particular, the tungsten trioxide (WO3) thin films exhibiting electrochromic properties have been studied extensively. While their optical switching properties are very well studied, not much study is focussed on their electrical properties, especially as a function of temperature. In this work we have studied the temperature coefficient of resistance (TCR) behavior of lithium atom intercalated WO3 thin films. Using the variable range hopping model we have calculated the density of states at the Fermi level of samples prepared by thermal evaporation and lithiated by a dry process. The TCR measurements were performed in the temperature range between 298 and 353K. The understanding of this temperature dependent electrical behavior is expected to enhance our knowledge of the electrochromic process in these films and lead to better design WO3 based electrochromic (EC) devices.