Low-pressure PECVD of nanoparticles in carbon thin films from Ar/H2/C2H2 plasmas:: Synthesis of films and analysis of the electron energy distribution function

A study of the synthesis of carbon nanoparticles embedded in carbon thin films deposited by radiofrequency (RF) (13.56 MHz) Ar/H-2 (4%)/C2H2 plasmas is presented. The carbon nanospheres exhibit an amorphous structure that is clearly observed at 300 W, under 0.1 Torr, and grows in size with increasing C2H2 between 1% and 20%. Above a C2H2 concentration threshold (20% in this case) carbon nanoparticles are no longer formed. In order to study possible changes in the plasma kinetics, optical emission spectroscopy (OES) is used to evaluate the electron temperature while changing the C2H2 concentration. In addition, an analysis of the temporal evolution of the electron energy distribution function (EEDF) is carried out for various C2H2 concentrations considering the effects produced by electron-vibrational superelastic collisions and relative concentration of excited Ar atoms. Finally, the morphological and tribological features of the deposited films are characterized.