Study On Fabrication Of Cuprous Oxide By Magnetron Sputtering And Photoelectric Properties Of Zn/In Doped

Cu₂O is a direct band gap semiconductor with the band gap of 2.1e V. Because of its high absorption coefficient, low-cost, non-toxicity, long-term stability, Cu₂O has potential applications in solar cells and photo catalysis. Theoretical calculations show that the photoelectric conversion efficiency of Cu₂O solar cells can be up to 18%, but in fact the highest efficiency that has ever reached is only 2%. Therefore, the fabrication of n type Cu₂O and the achievement of p-n homojunction to improve the photoelectric conversion efficiency have been the key research points. According to theories in semiconductor, doping is an important method to change the photoelectric properties and therefore in this paper doping on the basis of preparing phase-pure Cu₂O films was explored, and the effect of impurities on Cu₂O films and their photoelectric properties were investigated.Magnetron sputtering technology is a widely used vacuum coating method because in magnetron sputtering the ideal photoelectric properties can be realized by adjusting the target’s composition to dope the film. In this dissertation, phase pure Cu₂O was fabricated firstly with magnetron sputtering, then Zn or In doped Cu₂O, and finally Zn and In co-doped Cu₂O. The properties were studied. The detailed work is as follows:First of all, the condition of fabricating pure Cu₂O was investigated. By changing the substrate temperature, working pressure, sputtering power and O₂-Ar flow rate ratio, Cu₂O was obtained under 400 ℃, a working pressure of 2.0Pa with the Cu sputtering voltages of 350 V and 370 V, and with the sputtering powers of about 26 W and 37 W, respectively. The diffraction peak intensity shown from XRD changes along with the O₂-Ar flow ratio.Secondly, Zn-doped Cu₂O were fabricated based on the conditions of fabricating phase pure Cu₂O and characterized.With the Cu target voltage of 350 V and an O₂-Ar flow ratio of 1:44, XRD showed the film was a mixture of Cu₂O, Zn O and Cu. When keeping a Cu voltage of 370 V and O₂-Ar flow ratio of 1:28, XRD showed the result was pure Zn doped Cu₂O.Next, In-doped Cu₂O was fabricated based on the conditions of fabricating phase pure Cu₂O and characterized. Among the three parameters of Cu voltage of 350 V, In voltage of 330 V and O₂-Ar flow rate of 1:28, each time only one parameter was changed while the other two were fixed.When the Cu voltage and the O₂-Ar flow rate were fixed, XRD showed the result is phase pure In doped Cu₂O. The optical band gap was calculated by transmission spectrum obtained with UV-VIS spectrometer, and In doping results in no obvious variation. In a certain temperature range, Seebeck coefficient is negative.When the In voltage and the O₂-Ar flow rate were fixed, XRD showed the film is phase pure Cu₂O or Cu₂O with Cu. With higher doping of In, the optical band gap is widened, suggesting In doping can widen the optical band gap. In a certain temperature range, Seebeck coefficient is negative.When the Cu voltage and the In voltage were fixed, XRD showed the film is phase pure Cu₂O or mixed with Cu. There is no monotonous relationship between the optical band gap and Ar flow rate.In addition, Zn and In co-doped thin film was also prepared. However, this time the power of the Cu target used was different from last time and it was difficult to control the sputtering power, which led to too much metallic Cu in the films. Solutions are still in exploration.