Voie d’abord identique dans les ostéosynthèses ou arthroplasties pour fractures comminutives de l’humérus distal du sujet âgé : bases anatomiques

Abstract

Tantalum oxide (TaOx) films were grown on silicon substrates using the pulsed laser deposition (PLD) technique. The beam of a KrF excimer laser was used to ablate Ta2O5 targets in an oxygen background gas. The composition, structure, and optical properties of the films were investigated as functions of the O2 pressure (1–40 mTorr) and substrate temperature (150–800°C). Stoichiometric Ta2O5 films were obtained, with indices of refraction higher than 2.15 and extinction coefficients less than 10−4. Amorphous-like coatings were produced at deposition temperatures of 150, 250 and 400°C. At 650°C, a transition towards a polycrystalline structure was observed for O2 pressures higher than 1 mTorr. This transition involved β-Ta2O5 and an unidentified structure. At 800°C and an O2 pressure higher than 20 mTorr, β-Ta2O5 was the predominant phase. An investigation of the TaOx/silicon interface revealed the presence of an ultra-thin Ta-rich silicon oxide interlayer (∼2 nm) and a shallow Ta-rich silicon layer (<2 nm) at the silicon substrate surface. Within the processing window that led to stoichiometric Ta2O5, films were deposited on 75 mm diameter silicon wafers. The coatings were found to be uniform over the entire area in terms of thickness, composition, structure, and optical properties.