Photoluminescence and Raman scattering characterization of Cu2ZnSiQ4 (Q=S, Se) single crystals

► High quality Cu2ZnSiQ4 (Q=S, Se) single crystals were grown. ► PL spectrum of Cu2ZnSiS4 consists of near-band-edge emission lines and broad bands. ► Raman scattering study of the vibrational properties of Cu2ZnSiQ4 crystals. Photoluminescence (PL) and Raman scattering were used to characterize the single crystals of Cu2ZnSiQ4 (Q=S, Se). Thin-blade single crystals of Cu2ZnSiQ4 were grown by chemical vapor transport technique using iodine as a transport agent. PL spectrum of Cu2ZnSiS4 showed several near-band-edge emission lines and two broad bands at lower energy side, while only an asymmetric broad band was detected for Cu2ZnSiSe4. The vibrational properties and the influence of the anion substitution on the phonon spectra were studied by Raman spectroscopy. The substitution of sulfur by selenium leads to a down shift of about 169cm−1 for the most intense A1 mode due to the mass effect and lower force constants for the selenium containing compound.