Vanadium Pentoxide Alloyed with Graphite for Thin-Film Thermal Sensors

Abstract

The thermoelectric (TE) properties of vanadium pentoxide (V₂O₅) alloyed with graphite (G) were studied as a function of its incorporation percentage. Variable weight percentages of graphite powder (0–50%) were added to V₂O₅ powder and their mixtures were evaporated by a thermal evaporation technique to form thin films with a thickness in the range of 30–80 nm. In the infrared wavelength region, the transmittance of the obtained films increased as the G percentage was increased, while in the visible range, it decreased with G up to 10%. The TE properties were improved when G was in the range of 10–30%, while it decreased for the other percentages: Seebeck coefficient (S) changed from 0.6 mV/K to 0.9 mV/K and was zero with a G of 50%; the electrical conductivity varied slightly from 5 (Ωm)⁻¹ to 0.7 (Ωm)⁻¹ while the mobility improved from 0.07 cm²/V s to 1.5 cm²/V s and the respective carrier concentration was reduced, from 1 × 10¹⁸ cm⁻³ to 4 × 10¹⁶ cm⁻³. These films were applied as temperature sensors evaluating the thermovoltage as a function of thermal gradient between two electrodes, in which one was maintained at room temperature.