Improvement of temperature coefficient of resistance of a VO2 film on an SiN/polyimide/Si substrate by excimer laser irradiation for IR sensors

Using a laser-assisted sputtering process, we have successfully prepared a VO2 film on a SiN/polyimide/Si substrate. We investigated the effects of laser fluence and shot number on the crystallization and temperature coefficient of resistance (TCR) of the deposited VO2 films. At a constant shot number (2500 pulses), the resistivity of the film decreased from 50 to 60 mJ/cm2, and that of the film increased with an increase from 70 to 80 mJ/cm2. At 50 mJ/cm2, the resistivity decreased with increasing shot number. TCR at 30 °C of the amorphous VO2 film on a SiN/polyimide/Si substrate prepared by KrF laser irradiation at 50 mJ/cm2 for 4150 pulses at room temperature is 1.73%/K. In addition, TCR of the film prepared at 70 mJ/cm2 was 3.36%/K at 40 °C. This TCR of the film is much higher than that of the film (1.70%/K) prepared by thermal annealing, which is used in the present IR sensor. The VO2 films prepared by laser sputtering are promising materials for IR sensors, which are increasingly used in industry.