Novel synthesis, structural, linear and nonlinear optical properties of p-type kesterite nanosized Cu2MnGeS4 thin films

Abstract

This study presents the preparation of novel Cu2MnGeS4 thin films deposited on glass substrates, for the first time by an inexpensive spray pyrolysis technique. The crystal structure of the Cu2MnGeS4 samples was checked via the X-ray diffraction technique. The field-emission scanning electron microscope is used to investigate the surface morphology of the present films. Energy-dispersive spectroscopy has been employed to detect the compositional elemental percentage of thin films. Some structural parameters and defects, of the Cu2MnGeS4 samples, like the microstrain, the crystallite size, the dislocation density, and crystallites per unit surface area have been computed, studied and discussed. The experimental transmittance and reflectance spectra of the Cu2MnGeS4 samples have been measured to evaluate the linear and nonlinear optical parameters. The linear optical results indicate that Cu2MnGeS4 samples displayed a directly allowed optical transition and the optical energy gap values were reduced from 1.495 to 1.301 eV by increasing the thickness. Moreover, the dispersion parameters obtained and discussed via the Wemple-DiDomenico model. In addition, the nonlinear optical parameters of the Cu2MnGeS4 samples were computed and analysed. The hot-probe experiment indicates that the Cu2MnGeS4 films exhibited p-type conductivity.