Synthesis of tantalum pentoxide films by pulsed laser deposition: material characterization and scale-up

Tantalum oxide (TaO x ) films were grown on silicon substrates using the pulsed laser deposition (PLD) technique. The beam of a KrF excimer laser was used to ablate Ta 2O 5 targets in an oxygen background gas. The composition, structure, and optical properties of the films were investigated as functions of the O 2 pressure (1–40 mTorr) and substrate temperature (150–800°C). Stoichiometric Ta 2O 5 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 O 2 pressures higher than 1 mTorr. This transition involved β-Ta 2O 5 and an unidentified structure. At 800°C and an O 2 pressure higher than 20 mTorr, β-Ta 2O 5 was the predominant phase. An investigation of the TaO x /silicon interface revealed the presence of an ultra-thin Ta-rich silicon oxide interlayer (∼2 nm) and a shallow Ta-rich silicon layer (