Study on the influence of pulse modulation parameters on the characteristics of microwave Ar/CF₄ plasma jets

Plasma surface fluorination is one of the effective methods to enhance the surface insulation strength of insulating materials, and pulse-modulated microwave discharge is an important approach to generate high-performance fluorocarbon plasmas. To better achieve parameter control and performance enhancement of fluorocarbon plasmas, in this paper, pulsed microwave discharge is utilized to generate an atmospheric pressure Ar/CF4 plasma jet. The discharge morphology, reactive species, gas temperature, and electron density of the plasma jet are diagnosed, with a focus on investigating the influences of pulse modulation parameters (pulse modulation frequency and duty cycle) on the characteristics of the Ar/CF4 plasma jet. The results show that increasing the pulse modulation frequency leads to a decrease in jet length, concentration of reactive species, and electron density, and has little effect on gas temperature. The influence of duty cycle is opposite to that of modulation frequency. Under the parameters in this paper, the gas tem-perature can be controlled within the range of 329.22–382.82 K, and the electron density can reach the order of 1019 m−3. The research results can provide references for the application of plasma surface fluorination.