Effects of nitrogen ion irradiation on plasma polymerized films produced from titanium tetraisopropoxide–oxygen–helium mixtures

In this work films were produced by the plasma enhanced chemical vapor deposition (PECVD) of titanium tetraisopropoxide–oxygen–helium mixtures and irradiated with 150 keV singly-charged nitrogen ions (N +) at fluences, φ, between 10 14 and 10 16 cm − 2 . Irradiation resulted in compaction, which reached about 40% (measured via the film thickness) at the highest fluence. Infrared reflection–absorption spectroscopy (IRRAS) revealed the presence of Ti–O bonds in all films. Both O–H and C–H groups were present in the as-deposited films, but the density of each of these decreased with increasing φ and was absent at high φ, indicating a loss of hydrogen. X-ray photoelectron spectroscopy (XPS) analyses revealed an increase in the C to Ti atomic ratio as φ increased, while the O to Ti ratio hardly altered, remaining at around 2.8. The optical gap of the films, derived from data obtained by ultraviolet–visible spectroscopy (UVS), remained at about 3.6 eV for all fluences except the highest, for which an abrupt fall to around 1.0 eV was observed. For the irradiated films, the electrical conductivity, measured using the two-point method, showed a systematic increase with increasing φ.