Multi-photon Raman scattering and yellow–green-light emission from feather-like Cd_1–xZn_xS nanostructures

Abstract

Cd_1–xZn_xS (x ~ 0.5) alloy was synthesized on a silicon substrate by chemical vapor deposition in a horizontal tube furnace. Traditional analytical techniques such as scanning electron microscopy (SEM), transmission electron microscope, and Raman and photoluminescence (PL) spectroscopy were employed to characterize the samples. SEM analysis indicates that the branched nanorods are neatly perpendicular to the trunk and constitute a feather-like structure. Raman spectroscopy shows that the LO phonon modes of the feather-like Cd_0.5Zn_0.5S structures are blue-shifted about 3 cm⁻¹ with respect to pure CdS. PL properties of the samples show that the feather-like Cd_0.5Zn_0.5S structures have an asymmetric broad emission peak at 490–570 nm. However, the pure CdS has only one narrow emission peak at 510 nm. The Gauss fitting curves show that the broad emission peak at 490–570 nm can be fitted to four peaks at 465, 519, and 543 nm, respectively. The blue-light emission peak at 465 nm is considered to be the near-band-edge emission of feather-like Cd_0.5Zn_0.5S structures. Furthermore, the luminescence mechanisms of peaks 519 and 543 nm are discussed, respectively.