The role of the reactive atmosphere in pulsed laser deposition of bioactive glass films

Pulsed laser deposition (PLD) is a promising technique to produce bioactive glass coatings due to unique characteristic that allows depositing multicomponent films in stoichiometric composition. Moreover, when the ablation experiments are conducted in the presence of a reactive atmosphere (reactive pulsed laser deposition) the film composition can be enriched as compared to that of the basic target and the film properties can be tailored by varying the ambient gas pressure. In this work, the influence of different reactive atmospheres (N2O, H2O, NH3, Ar) and the role of the total pressure on the PLD bioactive glass film properties have been investigated. The coatings were produced by ablating a silica-based bioactive glass target with an ArF laser beam (193 nm, 4.17 J cm-2). Films were grown on silicon substrates at 200 deg. C. The bonding configuration changes were followed by Fourier transform infrared spectroscopy and the film thickness was measured by profilometry. The infrared spectra reveal that an oxidant environment (N2O, H2O) promotes the reduction of the non-bridging silicon-oxygen groups (Si-O-NBO) and the incorporation of carbonate groups and adsorbed water, while a NH3 and Ar atmosphere favours the formation of Si-O-NBO groups. The total pressure of the atmosphere also plays an important role on the film properties. When the Ar pressure is increased, a gradual shifting of the Si-O stretching vibration to higher wavenumbers, the incorporation of carbonates and the diminution of the Si-O-NBO groups were observed