Influence of the oxygen pressure on the physical properties of the pulsed-laser deposited Te doped SnO2 thin films

Tellurium doped tin oxide (Te:SnO2) thin films were prepared by pulsed-laser deposition (PLD) on glass substrates at different oxygen pressures, and the effects of oxygen pressure on the physical properties of as-grown and post-annealed Te:SnO2 films were investigated. The as-grown films deposited between 1.0 and 50 mTorr showed some evidence of diffraction peaks, with electrical resistivity of ∼8 × 101 Ω cm, but increasing the oxygen pressure up to 100 mTorr, three diffraction peaks (1 1 0), (1 0 1) and (2 1 1) were observed containing the SnO2 tetragonal structure, at 100 mTorr the electrical resistivity decreased abruptly at minimum value of 4 × 10−2 Ω cm, and increased reaching values of ∼4 × 10−1 Ω cm. The optical transmittance of the films increased with increasing oxygen pressure and high transmittance (∼87%) in VIS region by the films prepared at 100 mTorr and higher. The band gap of as-grown films was ∼3.5 eV corresponding at of the SnO2. After of post-annealed at 500 °C at atmospheric pressure for 30 min all films showed crystallization, and notable electrical resistivity changes were observed. The carrier density increased monotonically in the range of oxygen pressure between 1.0 and 100 mTorr, reaching values of ∼2 × 1018 cm−3, then, it decreased abruptly in films grown at 125 mTorr. While the mobility of the free-carrier decreased in the range of oxygen pressure between 1.0 and 100 mTorr, reaching minimum values of ∼5.8 cm2 V−1 s−1. The optical transmittance showed similar characteristic like the as-grown films. The figure of merit at 100 mTorr of as-grown films had value ∼1.2 × 10−5 Ω−1, and for post-annealed films at 100 mTorr the figure of merit was similar ∼1.7 × 10−6 Ω−1, indicating they were the better films.