Characterization of biocompatible Ti(CNO) layers on polymeric substrates

Abstract

This paper deals with the characterization of thin biocompatible Ti(CNO) films on polymeric substrates. The layers, deposited on polyvinylchloride (PVC) or polyester (PET) by plasma-activated chemical vapour deposition (PACVD), were analysed by X-ray photoelectron spectrometry (XPS), transmission electron microscopy (TEM) and neutron reflectometry (NR). Due to the low substrate temperature of less than 60 °C the Ti(CNO) layers are amorphous. Electron energy-loss spectroscopy (EELS) linescans performed in a scanning transmission electron microscope at near atomic (sub-nm) resolution indicates a 5–10 nm thick Ti gradient layer at the Ti(CNO) film/polyvinylchloride substrate interface. These findings are in agreement with neutron reflectometry results. Moreover, the results of neutron reflectometry confirm the composition of the Ti(CNO) films which were determined from analysis of X-ray photoelectron spectrometry data. The surface roughness of the deposited films is in the range of 2–9 nm. This low roughness is essential for biomedical applications in contact with blood, because a smooth surface minimises or prevents undesired adsorption of blood components. From neutron reflectometry studies it is evident that the thickness of the Ti(CNO) films can be varied between 20 and 300 nm without significant changes in composition and roughness.