Raman spectroscopy imaging and microstructure characterisation of Ag+ implanted TiO2 hybrid layers

• The hybrid oxidation process generates thin, uniform, and dense TiO 2 layers • The TiO 2 coatings consist of a diffusion layer and a PVD TiO 2 top layer. • The TiO 2 /Ag+ layer has amorphous and crystalline character and consists of rutile and anatase. • Raman spectroscopy could determine rutile/anatase concentration in TiO 2 thin layers. • Produced layers seems attractive solution for improving titanium alloys' bioactivity The paper presents research on Ag + ions implanted TiO 2 thin layers with Raman spectroscopy imaging. The oxide layers were formed on Ti–6Al–4V ELI titanium alloy substrates through a multistage hybrid oxidation process, which combines fluidised bed (FB) diffusive treatment at 640°C for 8 hours with physical vapor deposition (PVD) pulse magnetron sputtering. Silver ions were implanted into the TiO 2 layer after the fluidised bed process using a Metal Vapour Vacuum Arc implanter to form an interface for further PVD oxidation and generate an antibacterial interface that prevents inflammation during top layer spallation and cracking under working conditions. The ion implantation process was preceded by Monte Carlo simulations modelling of the depth profiles using SRIM-2013.00 software. The fluence of implanted ions was 1×10 17 cm -2 , and the acceleration voltage was 60 kV. The modelled range at peak damage of the real Ag + + Ag 2+ + Ag 3+ + Ag 4+ profile was about 40 nm. Raman spectroscopy imaging, XRD, SEM and TEM observations were carried out to evaluate the effects of ion implantation, analyse oxide phases and determine the mechanism of TiO 2 layer formation during combined oxidation. The layers exhibited both amorphous and crystalline characteristics, and the top surface area was composed of TiO 2 rutile and anatase, as well as oxygen vacancies (at 750 cm -1 ) and crystalline TiO 2 (at 310 cm -1 ). Amorphous TiO 2 dominates in the middle and near substrate layer. The layer before the substrate is composed of Ag + ion area (ca. 100 nm) and dense TiO 2 mixture of rutile (236 cm -1 ) and partially anatase (141 cm -1 ). Ultimately, it has been found that the functionalisation of oxide layers using a multistage hybrid oxidation and ion implantation process leads to a change in oxygen concentration in the various TiO 2 layers forming a highly defected and active top surface layer. The homogeneous multiphase oxide layers on Ti alloys implanted with Ag + ions for generating an antibacterial interface might improve the bioactive properties, which in perspective might be essential for biomedical applications.