Modeling Phase Changing Property of VO2 for Reconfigurable Microwave Frequency Selection Applications via Time-Resolved Microwave Conductivity

Vanadium dioxide (VO2) is characterized using the time-resolved microwave conductivity (TRMC) method for applications requiring reconfigurable microwave frequency selection. We demonstrate that TRMC is a flexible method for determining the microwave conductivity of thin film compounds of varied thicknesses that are both phase-changing and non-phase changing in nature. The method makes use of Ka-band microwave resonant waveguides to examine how thermally excited samples' microwave conductivity changes in response to microwave-transmitted power through the system's sensitivity factor. The sensitivity factor is illustrated by a study of incident waves (electromagnetic fields) on medium and waveguide perturbation analysis in VO2 thin films. The TRMC measurements show a low regime in the microwave conductivity below the transition temperature (Tc) of VO2 where Tc occurs near 65 degrees C; this is associated with the dielectric characteristics of the charge carriers and points to the presence of shallow trap electron states. Longer electron hops enhance charge mobility and, consequently, the barrier energy above Tc, where these states are thermally discharged, resulting in a high thermally triggered microwave conductivity regime. The activation energy may come from a variety of complex contributions, like polaronic self-localizations, as well as a dynamic disorder brought on by the thermal oscillations of VO2 molecules. The calculated conductance values are simulated in CST Studio as plane wave incidence on medium to ascertain the fields' microwave transmission behavior and contrast it with the experimental results to validate the model. Additionally, using the derived conductivities, the characteristics of well-known materials like copper (Cu) were confirmed.

Automated summary

This study characterizes vanadium dioxide (VO2) using the time-resolved microwave conductivity (TRMC) method, which is suitable for applications requiring reconfigurable microwave frequency selection. The TRMC method is shown to be flexible in determining the microwave conductivity of thin film compounds of different thicknesses, whether they are phase-changing or non-phase changing. The method utilizes microwave resonant waveguides to examine the changes in microwave conductivity of thermally excited samples in response to microwave-transmitted power, represented by the system's sensitivity factor. The measurements reveal a low regime of microwave conductivity below the transition temperature (Tc) of VO2, associated with dielectric characteristics and shallow trap electron states, and a high thermally triggered microwave conductivity regime above Tc, where longer electron hops enhance charge mobility.