The effect of Substrate temperature on physical and electrical properties of DC magnetron sputtered (Ta 2O 5) 0.85(TiO 2) 0.15 films

Thin films of (Ta ₂O ₅) _0.85(TiO ₂) _0.15 were deposited on quartz and p-Si substrates by DC reactive magnetron sputtering at different substrate temperatures (T _s) in the range 303 - 873 K. The films deposited at 303 ⁰K were in the amorphous and it transformed to crystalline at substrate temperatures ≥ 573 ⁰K. The crystallite size was increased from 50 nm to 72 nm with the increase of substrate temperature. The surface morphology was significantly influenced with the substrate temperature. After deposition of the (Ta ₂O ₅) _0.85(TiO ₂) _0.15 films on Si, aluminium (Al) electrode was deposited to fabricate metal/oxide/semiconductor (MOS) capacitors with a configuration of Al/(Ta ₂O ₅) _0.85(TiO ₂) _0.15/Si. A low leakage current of 7.7 × 10 ^-5 A/cm ² was obtained from the films deposited at 303 K. The leakage current was decreased to 9.3 × 10 ^-8 A/cm ² with the increase of substrate temperature owing to structural changes. The conduction mechanism of the Al/(Ta ₂O ₅) _0.85(TiO ₂) _0.15/Si capacitors was analyzed and compared with mechanisms of Poole-Frenkel and Schottky emissions. The optical band gap (E _g) was decreased from 4.45 eV to 4.38 eV with the increase in substrate temperature.