The influence of atmospheric pressure plasma jet on oxidative termination of diamond surface

This study investigates the effects of atmospheric pressure plasma jet on diamond surface functionalization, which is key for plasma-assisted polishing. By varying plasma parameters including voltage waveforms, substrate temperature, reactive gas composition, and flow rate, we identify conditions that enhance hydroxyl and atomic oxygen radical formation and promote sp3-to-sp2 carbon conversion. Pulsed and sinusoidal waveforms are compared, along with the influence of pulse rise and fall times. Optical emission spectroscopy and x-ray photoelectron spectroscopy analyses show that pulsed voltages with short rise and fall times and higher substrate temperature significantly enhance surface oxidation. Increasing gas flow facilitates the generation of excited species, producing more oxygen and hydroxyl terminations. Oxygen addition quenches plasma, and the maximum hydroxyl radical yield is observed at 1500 ppm humidity.