Transparent conductive F-doped SnO2 films prepared by RF reactive magnetron sputtering at low substrate temperature

To obtain highly transparent conductive F-doped SnO2 films by magnetron sputtering at low substrate temperatures, a new method of sputtering high-density SnF2-Sn target in Ar + O-2 atmosphere was adopted in the present study. The structural, electrical, and optical properties of the films prepared were investigated as a function of O-2 flux. The results indicate that the films shows SnO2 phase only at O-2 flux above a critical value (0.8 sccm), and the crystallinity of SnO2 phase is improved with increasing O-2 flux. The resistivity of the films steeply decreases once O-2 flux is above the critical value, but it greatly increases as O-2 flux is too high. Only in intermediate range of O-2 flux, the films with low resistivity can be obtained. As O-2 flux is above the critical value, both the transmittances in visible light range and E-g of the films show steeply increase, and the PL spectra of the film show distinct emission characteristics. Furthermore, the position and intensity of PL emission peaks are similar when O-2 flux is above the critical value, and the emission mechanism can be attributed to electron transitions mediated by defect levels in the bandgap, such as V-O and F-O. Just because of formation of SnO2 phase in the films and existence of relatively larger amount of V-O and F-O, the films show low resistivity and high transmittance at suitable O-2 fluxes.