Growth and treatment of hydrogenated amorphous carbon nanoparticles in a low-pressure plasma

A parallel-plate, low-pressure plasma for fundamental nanodusty plasma research is used to grow hydrogenated amorphous carbon nanoparticles using an argon-acetylene gas mixture. The particles stay confined in the volume of the argon plasma after turning off the C 2 H 2 gas flow and the effects of prolonged treatment with noble gas (Ar) and reactive gas mixtures (Ar/ H 2, Ar/ D 2, or Ar/ O 2) are investigated using in situ infrared absorption spectroscopy. Additionally, ex situ scanning electron microscopy imaging of extracted nanoparticles is used to analyze their size and surface morphology. In 45 min of argon treatment, a size increase of about 50% is seen together with a decrease in sp 2 CH x bonds and an increase in CO bonds, indicating incorporation of oxygen from gas impurities into the particle material. All reactive gas mixtures lead to the expected etching of the nanoparticle material without any exchange reactions between gas-phase deuterium and surface-bonded hydrogen atoms. These results are important for in situ studies of nanoparticle clouds such as dust density wave diagnostics, but they also provide fundamental information about plasma interaction with a-C:H material.