Preparation Of P-type Cu₂O Thin Films By RF Magnetron Sputtering And Properties Research

Cu₂O is a p-type semiconductor material, which has several unique advantages amongcommonly used semiconductors, such as being earth abundant, nontoxic and environment friendly. Inaddition to its well-established applications in photocatalytic, corrosion prevention and other areas,Cu₂O is also greatly appealing to the photovoltaic industry due to its low cost.In this thesis, the property of Cu₂O thin film was introduced, as well as its preparation methodsand application in solar cells. To show its theoretical feasibility, geometry structures, band structuresand density of states of Cu₂O, both before and after N-doped were investigated in detail. Firstprinciples pseudo-potential methods based on density functional theory was adopted in the calculation.On top of the theoretical analysis, the effects of O₂and N₂flow rate on Cu₂O thin films growth wasstudied, in which case Cu₂O were prepared by reactive magnetron sputtering. Finally, p-type Cu₂Oheterojunction thin films were prepared on Si, FTO and AZO substrates, respectively.And itsapplication on thin film solar cells was also discussed over the results.All experiments in the thesis indicated that, ionic bonding is preferable in ideal Cu₂O. Eventhough Cu₂O is defined as metal oxide semiconductor composed by both ionic and covalent bonding.Its normal band gap at G point is0.483eV. However, after N doping, the band gap was increased to0.536eV, showing shallow acceptor level had been created. This proves that the preparation ofN-doped p-type Cu₂O is possible.The composition of Cu₂O is heavily dependent on oxygen flow rate. As oxygen flow rateincreased, the main component of the sample shifted through Cu, Cu₂O to CuO, accordingly.. Whenthe oxygen flow rate is at4.2sccm, well crystallized Cu₂O thin films with low surface roughness andhigh transmittance rate were obtained. By setting the ratio of N₂/O₂at0.6, Hall mobility wasincreased from2.0×1016cm-3to2.2×1019cm-3, and band gap from2.29eV to2.47eV. Thecomposition of N elements in the film is3.41%at this moment. The interface between Cu₂O and AZOis constructed between （111） Cu₂O and （002）ZnO planes, showing it has a strongly preferred growingdirection. And the lattice mismatch is caculated to be7.1%. Cu₂O thin film deposition on AZOsubstrate served better for heterojunction structure compared to Si or FTO, due to their superiorinterface property.