LAUSR

Abstract The present study reports the phonon modes in the pentanery compound semiconductor (AgxCu1-x)2ZnSnS4 (ACZTS) (0 ≤ x ≤ 1) as identified using Raman Spectroscopy. When traversing from Cu2ZnSnS4 (x = 0) to Ag2ZnSnS4 (x = 1), the Raman shifts corresponding to B(TO), B(LO) and E(TO) modes that occur at 254, 285 and 307 cm−1, respectively, decreased to 223, 269 and 295 cm−1. Such a gradual change in the Raman shift corresponding to Cu2ZnSnS4 (CZTS) upon Ag-alloying is a characteristic of one-mode behavior. On the other hand, there was no change in the Raman shifts corresponding to the modes A1, E(LO), B2(TO) and B2(LO), that remained at 332, 348, 360 and 371 cm−1, respectively; this observation along with the fact that Raman shift for the A-mode started appearing both at 336 and 345 cm−1 with Ag-alloying, suggest that the Raman scattering in the ACZTS compounds most likely demonstrate the two-mode behavior. Further, with increased Ag-alloying the ratios I285/I302 and I336/(I364 + I371) derived from the Raman spectra increased from 1.44 and 1.96, to 2.49 and 2.43, respectively, which indicates that the extent of disorder decreased in CZTS with Ag-alloying; this was further supported by the dramatic changes observed in the hole-type carrier density which is strongly affected by the disorder.