Effect of the Sb content in the SnO2 lattice and N2 percentage in a mixed sputtering gas on the N solubility in SnO2 films

Abstract

Herein, the hole concentration of a SnO2 film has been increased by the co-doping of Sb and N in the SnO2 host lattice. The N-substituted O content in the SnO2 lattice was observed to depend on the N2 gas percentage in a mixed sputtering gas (comprising Ar and N2) and the Sb-substituted Sn content in the host lattice. The N-substituted O content in the SnO2 lattice increased with N2 gas concentration in the mixed sputtering gas and the Sb2O3 content in the STO (Sb2O3- doped SnO2) target. An optimal number of N-substituted O and Sb-substituted Sn contents occurred for the target with 6 % wt. Sb2O3 and the mixed sputtering gas with 75 % N2, respectively, owing to the high electrical conductivity and the best crystal quality. N-substituted O and Sb-substituted Sn contents were detected using X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, ultraviolet-visible spectroscopy, and XRD pattern measurements. The N-substituted O sites in the host lattice are large enough to cause the tetragonal rutile-to-cubic phase transformation. The film crystal quality of the cubic phase is higher than that of the rutile one. The lowest resistivity and the highest hole mobility were measured to be 1.0 × 10−2 Ω cm and 4.26 cm2 V−1 s−1, respectively, corresponding to the hole concentration of 1.24 × 1020 cm−3. The electrical property and the crystal quality of p-type Sb- and N- co-doped SnO2 films were improved compared to Sb- or N- doped SnO2 films. The deposition temperature dropped 300 °C for Sb- or N- co-doped SnO2 film instead of 550 °C for Sb-doped SnO2 film. The I–V plots of SNTO-6-y/n-Si junctions under dark and light conditions corroborated that the conductive SNTO-6-y films are p-type. The results showed that the photocurrent for SNTO-6-75 diode achieves the highest value due to the high crystal quality and the low surface roughness of SNTO-6-75 film compared to the other films. The on-off photocurrent response confirmed the stable reproducibility of the SNTO-6-75 diode. The photo-electronic effect of p-type Sb- and N- co-doped SnO2 films is promising to apply for photodetector or the other optoelectronic devices.