Investigation of chalcopyrite film growth at various temperatures: analyses from top to the bottom of the thin films

We reported a new method to investigate the phases and structures of thin film bottom parts. The films were polished by flapping papers to reach the bottoms. The surfaces and cross sections of thin films were observed by Scanning Electron Microscopy. Grazing Incidence X-ray Diffraction, Raman spectra and X-ray Photoelectron Spectroscopy (XPS) were used to investigate the phases, structures and chemical components of the surfaces and bottoms of thin films. By this method, we studied the growth processes of chalcopyrite films after the selenization at various temperatures from 270 to 600 °C. At 270 °C, a great amount of Cu–Se nodules formed at the surface, while (In,Ga)–Se stayed in the bottom. At 380 °C, a double layer structure was observed in the film. The top part was typical CuInSe₂ polycrystalline, while the bottom part contained complicated components, like CuInSe₂, Cu(In,Ga)₃Se₅, (In,Ga)Se. At 600 °C, a single layer was formed, which was composed of Cu(In,Ga)Se₂ phase. However, a higher Ga/(In+Ga) ratio was obtained towards the back contact. In addition, XPS indicated that the Mo/Cu(In,Ga)Se₂ interface was rich in Ga and Se.