Modification of electrical properties of amorphous vanadium oxide (a-VOx) thin film thermistor for microbolometer

Abstract

This work reports on the modification of electrical properties of amorphous vanadium oxide (a-VOx) thin film thermistor by growth temperature and its effects on the performances of a cooler-free microbolometer. The a-VOx thin films have been deposited by pulsed DC sputtering processes under various growth temperatures from 160 to 230 ℃. The sheet resistance of the samples at room temperature decreases from 330 to 70 kΩ/▢ with increasing growth temperature. This is due to the increase of oxygen vacancies at higher growth temperature, which have been confirmed by XPS analysis. Temperature dependence of resistance of a-VOx films shows non-hysteresis behaviors up to 120 ℃, which in turn shows clear activation energies. The activation energy of a-VOx films also decreases from 0.190 to 0.145 eV with increasing growth temperature, which confirms the decrease of temperature coefficient of resistance (TCR) from 2.80 to 2.44 (-%/K) at 25 ℃ and from 1.48 to 1.14 (-%/K) even at 120 ℃. The responsivities of fabricated microbolometers based on the a-VOx thin film thermistors have been measured from 3.04 × 103 to 1.14 × 103 V/W at room temperature and from 9.54 × 102 to 3.02 × 102 V/W even at 120 ℃ with increasing growth temperature.