Reasearch On VO₂ Thin Films Prepared By Pulsed DC Magnetron Sputtering Technology

Single crystal VO₂ undergoes a reversible semiconductor-metal phase transition in the vicinity of 68?,and the optical and electrical properties of VO₂ can be changed in femtoseconds.This novel characteristics have a widely application in various devices,such as infrared detectors,optical switches and smart windows,etc.In this paper,a pulsed reactive magnetron sputtering technique was used to prepare the VO₂ film.The influence of the parameters such as pulse frequency,pulse duty,deposition temperature and working pressure were researched.The growth mode of VO₂ films prepared by pulsed reactive magnetron deposition have been analyzed based on the experimental results.All the samples in this research were prepared by pulsed magnetron reactive sputtering.Firstly,VO₂ thin films were prepared at different pulse duty cycle and pulse frequency.The effect of pulse supply parameters on the photoelectric properties of VO₂ thin films were studied.The results showed that the plasma of sputtering process can be effectively changed by adjusting the pulse duty cycle.And the actual sputtering time can be controled by changing the pulse duty cycle.The composition,crystallization and deposition rate of VO₂ films can be adjusted by changing duty cycle.Reduction of the pulse duty cycle can effectively restrain target arc discharge,target poisoning,et al.The crystal and grain size of VO₂ films,optical transmittance and electrical conductivity can be modified by adjusting the pulse frequency.The deposition temperature of VO₂ thin films at 440?showed excellent phase transition properties.The results revealed that the solar energy modulation ability in near infrared range is 11%and the phase transition amplitude of sheet resistance is about three orders of magnitude.VO₂ films with high phase transition performance were prepared by pulsed magnetron reactive sputtering with substrate bias at the low sputtering temperature of 300?.According to the experimental results,the pulsed magnetron reactive sputtering with magnetron reactive sputtering with substrate bias at the low temperature of 300?.Rhe experimental results showed that the pulsed magnetron reactive sputtering with substrate bias can provide more energy to the growth of the thin film than direct current reactive magnetron sputtering.The substrate bias make a great affect on photoelectric properties of VO₂ films,the transition temperature would decrease with the substrate bias increased.The transition performance of VO₂ films,which deposited at 300?with 100V substrate bias is close to the films prepared at 440?.VO₂ thin films were deposited at different working pressure.According to the experimental results,VO₂ films exhibited weaker transition properties with the working pressure decreased.Due to the working pressure decreased,collision probability between the sputtering target atoms and the gas molecules decreases,which resulted in target atoms moving to the substrate with more energy.On the one hand,increasing energy from target atoms promote the growth of the thin films.On the other hand,the velocity of the target atoms increase result in the increase of intrinsic stress,transition temperature and thermal hysteresis width.