The Preparation And Characterization Of SnO₂:Al/Zn Transparent Conductive Thin Film

Tin oxide (SnO2) is one of the most important transparent conductive oxide (TCO) materials which has numerous applications in modern technologies such as flat panel displays, solar cells, light emitting diodes and also gas sensors due to its attractive properties with wide band gap (Eg=～3.6 eV), high electrical conductivity, high transmittance in the ultra violet (UV)-visible (VIS) region and high infrared (IR) reflectance, abundance in nature and absence of toxicity. However, almost all the TCO films (e.g., In2O3:Sn, SnO2:F) are n-type conducting, and most of the p-type TCO films are in researching to fabricate transparent pn junctions which are necessary for transparent electronic devices.In this paper, the p-type conducting SnO2:Al and SnO2:Zn film derived from thermal diffusion of a sandwich structure Al/SnO2/Al and Zn/SnO2/Zn multilayer thin films deposited on quartz substrate have been prepared by direct current (DC) and radio frequency (RF) magnetron sputtering. The effects of thermal diffusing temperature and time on the structural, electrical and optical performances of SnO2:Al and SnO2:Zn multilayer thin films have been studied. Treatment at 450℃for 4 h was found being the optimum annealing parameters for p-type SnO2:Al films to obtain relatively high hole concentration of 7.224×1018 cm-3 and low resistivity of 0.814Ω·cm, respectively. The transmission of the p-type SnO2:Al films were above 80%. The electrical and optical performances of SnO2:Al films are superior to SnO2:Zn films fabricated by the exactly same poreess which shows that Al doping is more effective than Zn doping in SnO2.In addition, zinc doped tin oxide were deposited on quartz substrates by the radio-frequency (RF) magnetron sputtering using a ZnO doped SnO2 ceramic target. The effect of substrate temperature on the structural, electrical and optical performances of SnO2:Zn films has been studied. SnO2:Zn thin film showed stable n-type conductivity. The highest carrier concentration of -1.144×1020 cm-3 for the film with an average transmittance of about 80.0% in the visible region and the lowest resistivity of 1.116×10-2Ω·cm were obtained when the SnO2:Zn films deposited at 250℃. Meanwhile, with increasing substrate temperature, the grain size and roughness of SnO2:Zn thin film increased.