Erosion of a-C:H in the afterglow of ammonia plasma

Amorphous hydrogenated carbon (a-C:H) deposits were eroded in the afterglow of a NH3 plasma, created with an inductively coupled RF generator in pure NH3 at the gas pressure of 50 Pa. The plasma system was characterised by optical emission spectroscopy and mass spectrometry, and the erosion process was monitored in-situ with a laser interferometry system. Based on the mass spectrometry measurements, the degree of dissociation of the NH3 molecules was estimated at 90% at the highest generator forward power in the discharge region, however the densities of N and H atoms were significantly smaller at the location of the sample holder. The erosion rates were found to increase with surface temperature and forward generator power. In the high dissociation regime, the composition of the afterglow and the reaction products highlight the role of N atoms in the erosion process.