Vanadium oxide plays a crucial role as the temperature-sensitive layer of microbolometers. This layer should possess a high temperature coefficient of resistance (TCR) along with a desirable resistivity suitable for readout electronics. Mixed phase vanadium oxide thin films (VxOy) consist of different ratios of pure phases, which affect the resultant resistivity and TCR. It is thus important to be able to control individual phase concentrations to obtain the desired resistivity and TCR. In this study, we show that W-doping does not only introduce a new W-phase but also supports the formation of new V-phases in addition to the change in relative ratios of the original phases. The new V-phase, V2O5, dominates the overall electrical properties. Here, we first present the formation of new phases with W-doping and the structural and electrical characterization with classical tools, and then we show that Terahertz Time-Domain Spectroscopy (THz-TDS) is a strong nondestructive characterization technique that can monitor these effects of doping especially on the electrical behavior of VxOy films. Exploration of the control of this behavior is essential for the fabrication of a high TCR film with a desirable resistivity. (C) 2022 Elsevier B.V. All rights reserved.