Investigation of chalcopyrite film growth: An evolution of thin film morphology and structure during selenization

In this work, we report a study of the evolution of Cu-In-Ga-Se system during selenization. The metallic precursors were selenized in Se vapour atmosphere at temperature range from 210 to 380 C. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra were used to investigate morphological and structural properties of the films. A great amount of thin platelets appeared in the film surfaces at temperature range from 210 to 270 C. Most platelets had hexagon or polygon structures. The average sizes of these platelets increased with the temperatures. TEM analyses indicated that these platelets had γ-CuSe phases. Beyond 310 C, most of CuSe platelets decomposed under release of selenium and formed Cu_2-xSe. Cu_2-xSe might react with InSe for the formation of tetragonal CuInSe₂. The average grain sizes increased obviously with the increased temperatures. A possible reaction path to obtain a chalcopyrite structural film was discussed in the end. In addition, Ga was detected rich in the bottom of the film by energy dispersive spectroscopy and grazing incidence X-ray diffraction.