Thin polycrystalline diamond films were deposited on prepared (100) Si substrate by hot filament chemical vapor deposition using a mixture of hydrogen, propane-butane and argon. During investigations the gas flow of argon was varied from 100 sccm to 400 sccm. Scanning electron microscopy analysis revealed that the addition of argon to the gas phase influenced the growth rate and film structure. An increase of argon concentration provokes an increase in film porosity and decrease in crystalline facetting. The quality of these films was investigated with the use of the Raman spectroscopy.

Surface conductivity of thin diamond films was measured as a function of temperature up to 450• C. Hydrogenated diamond was synthesized by chemical vapor deposition in hydrogen/carbon plasma. Low values of charge carrier activation energy (≈ 10 meV) were observed, when hydrogenated diamond films were exposed to the ambient humid air. However, the activation energy increased by two orders of magnitude as film temperature exceeded 300• C. We have attributed this behavior to the desorption of the H2O adlayer. The jump of the activation energy did not occur, when experiment was performed in vacuum. We have also shown that donor doping leads to the up-shift of the Fermi level much above the acceptor-like band gap levels induced by surface C-H bonds, which cannot be compensated by transfer of electrons from diamond to the double H-H2O layer.