Crystal growth and characterization of the cubic semiconductor Cu_(2)SnSe_(4)

摘要

X-ray powder diffraction study of the p-type semiconductor Cu_(2)SnSe_(4) shows that this material crystallizes in the cubic structure, space group F43m, with unit cell parameter a=5.6846(3) A. The temperature variation of the hole concentration between 120 and 300 K, obtained from the Hall effect and electrical resistivity measurements, is due to the thermal activation of an acceptor level with ionization energy of about 0.02 eV. The temperature variation of the hole mobility is explained by considering the scattering of charge carriers by ionized impurities and acoustic phonons. From this analysis, the density-of-states effective mass of the holes is estimated to be about 0.8 m_(e), m_(e) being the free electron effective mass. From the optical absorption spectra, the fundamental absorption edge is found to be direct. The value of the lowest energy gap and the spin-orbit splitting were estimated to be about 0.35 and 0.20 eV, respectively. The temperature dependence of the magnetization measurements shows that Cu_(2)SnSe_(4) is paramagnetic, indicating that most of the copper atoms have the divalent charge state.