Properties of DLC thin films produced by RF PE−CVD from pyrrole monomer

This paper reports the properties of diamond like carbon (DLC) thin films obtained in a capacitively coupled, RF powered, plasma enhanced chemical vapor deposition (PE−CVD) system. A precursor used was pyrrole, one of the most known monomers for conductive polypyrrole polymer processing. The deposition rate of thin films was high: 74 nm/min at 50 W and 425 nm/min at 400 W input power. The hardness and elastic modulus of thin films reached the highest values of 16.5 and 148 GPa at 400 W and the surface morphology of the films did not suffer important changes in the interval of utilized input powers: RMS roughness decreased from 0.45 nm at 50 W to 0.20 nm at 400 W. All deposited films were transparent in the infrared range. Raman measurements revealed that the increase of the input power led to a decrease of the sp3 and an increase of sp2 bonded carbon atoms in thin films. The resistivity of DLC thin films was very high for low values of RF input power (ρ > 107 kΩ cm) and decreased at higher values of input power (ρ ≈ 55 kΩ cm at 400 W). By using nitrogen as a doping element the resistivity decreased to ρ ≈ 3.5 kΩ cm at 400 W and 20 sccm N2.