(376c) Novel Study on Mixed Ultra-Thin Films of Titanium and Zirconium Oxides on Titanium Implant Abutment Surfaces Using Atomic Layer Deposition

To date, titanium alloys have been used in a wide range of biomedical applications such as dental, and orthopedic implants, due to their biocompatibility, non-toxicity, mechanical properties, corrosion resistance, and being biologically inert. However, one of the main drawbacks of titanium alloys is microbial adhesion to their surface. Atomic layer deposition (ALD) is a promising technique to deposit highly uniform, conformal, and pinhole-free thin films on a variety of substrates through sequential and self-limiting reactions. ALD has been chosen because of its capability to deposit ultra-thin films in nanometer scale with excellent composition tenability, precise thickness control, strong chemical bonding between the coating and substrate, reproducibility, and being applicable to metallic substrates such as Ti(V) alloys. This study aims to systematically investigate the effect of ALD films of titanium and zirconium mixed oxides on surface characteristics of titanium alloy abutments. Such surface improvements would decrease the microbial adherence and biofilm formation on the surface, which is essential in biomedical and dental applications of implants placed in human body. Type V Titanium discs were polished to 2500 grit. ALD was used to deposit mixture of TiO₂ and ZrO₂ film at 120 °C with expected 4:1 thickness ratio on the experimental group discs with non-coated discs as control. The ALD precursors and oxidizer were tetrakis(dimethylamido)titanium (TDMAT) and tetrakis(dimethylamido)zirconium (TDMAZ), and ozone, respectively. The samples were annealed at 700°C for 1 hour in nitrogen environment. Spectroscopic ellipsometry was used to measure the film thickness on silicon reference (i.e., 26.3±0.5 nm with a growth rate of 0.03 nm/cycle). The presence of both Ti and Zr as well as the approximate Ti:Zr ratio of 4:1 were confirmed with X-ray Photoelectron Spectroscopy (XPS). The surface roughness and hydrophilicity were tested for both groups using Optical Profilometry and Water Contact Angle (WCA) measurement, respectively. Pre-deposition roughness average was 0.16 µm, which was slightly increased to 0.22 µm after deposition. The coatings resulted in super hydrophilic surface with increasing wettability by over ~90%. Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS) were performed to study the annealing effect on the morphology of the coatings. Based on SEM and EDS, the film morphology was changed after deposition and annealing. Appearance of white dots after deposition would suggest the island growth of ZrO₂ on a uniform film of TiO₂. The reason might be the lower cycle numbers of ZrO₂ (2 cycles) compared to TiO₂ (16 cycles). Increase in grain sizes is observed after annealing that might be due to the crystallinity of metal oxides. A more detailed study of crystallinity with other techniques as well as microbial attachment of the samples are ongoing and recommended for future study.