Optical absorption, Raman spectra, and electrical properties of Mn-doped Cu2SnSe3 semiconductor compound

Here we report a study of the absorption spectrum of Mn-doped bulk crystal samples of Cu2SnSe3 which are also characterized by X-ray diffraction (XRD), electrical properties, and Raman spectroscopy. From the electrical data it is found that above 145 K the electrical conduction is mainly due to activation in the valence band and below this temperature due to variable-range-hopping of Efros–Shklovskii type in the impurity band. Our XRD and Raman data show the presence of SnSe and SnSe2 binary secondary phases in this compound. From the absorption coefficient data at room temperature the fundamental absorption edge is determined to be direct with a band gap energy of EG = (0.41 ± 0.01) eV. An additional indirect band-to-band transition above 0.9 eV, probably related to the band gap of SnSe, is observed.