Microstructure and properties of titanium oxide synthesized by metal vacuum arc deposition

Summary form only given, as follows. Titanium and Ti6A14V alloy are attractive biomaterials with good compatibility with tissues, bones, and blood. It is known that a surface oxide film on titanium plays an important role in its biocompatibility. The protective titanium oxide layer, albeit thin, is key to the excellent corrosion resistance, but does not preclude interactions with the environment. Release of titanium ions can impose a significant inhibiting effect on the mineralization process during bone formation. However, sensitization and influences on humoral and cellular immunity make titanium a chemical carcinogen. Release of aluminum ions may lead to neurological disorders such as dialysis dementia, Alzheimer's disease, and bone diseases including vitamin D refractory osteodystrophy, hypercalcaemia and anaemia. Vanadium ions are mainly associated with irreversible enzymatic disturbance as well as inhibition of the bone mineralization process. Hence, it is necessary to synthesize a thicker titanium oxide film on titanium or titanium alloys. In this work, TiO/sub 2/ films were deposited on silicon[100] substrates using metal vacuum arc deposition. The base pressure of the system was 2×10/sup -3/Pa. The deposition conditions were: metal arc pulse frequency = 60Hz, metal arc pulse duty = 1ms, metal arc current = 180A, metal arc main current = 0.8A, substrate voltage =--60V, oxygen flow rate = 4.1 to 25sccm, operating pressure = 0.85× 10/sup -2/ to 3×10/sup -2/Pa. The as-deposited samples were annealed at 800°C for 30min at a pressure of 8.0×10/sup -4/Pa. The film composition was determined by RBS and the surface morphology was studied by AFM. XRD shows that the as-deposited films consist of primarily anatase TiO/sub 2/[213] and anatase TiO/sub 2/[204]. The phase and orientation of the as-deposited films show no noticeable change with increasing oxygen partial pressure, but after annealing, the films become rutile TiO/sub 2/[010][101][200][211][002] and the preferred orientation changes from [110] to [101] and [002] at high oxygen pressure. XRD and contact mode AFM disclose that the as-deposited films are quite dense and composed of grains 80 - 100 nm in size whereas the annealed films have larger grains exceeding 400 nm. The hardness and adherence strength of the substrate and films are assessed using the CSEM nano-hardness and nano-scratch testers.