Deposition position tunability of size in CdS nanobelts and their photoluminescence

Abstract

Cadmium sulfide (CdS) nanobelts with different sizes were synthesized through one-step high-temperature solid-vapor and condensation process. The structural and optical properties of these CdS nanobelts were investigated. X-ray diffraction (XRD) patterns indicate that both samples have a hexagonal wurtzite structure. The Raman spectra clearly show the first and second order longitudinal optical phonon modes of CdS. Photoluminescence properties of both samples were characterized using a fluorescence spectrometer at room temperature. The results show that CdS nanobelts with the smaller size have two emission bands: a weak emission at 507 nm and an asymmetric, broad emission in the region at 600–830 nm. Further, the asymmetric, broad emission can be fitted to five emission peaks at 657 nm, 681 nm, 699 nm, 756 nm and 812 nm, respectively. In addition, the CdS nanobelts with the larger size have an asymmetric, broad emission band between 500 nm and 700 nm, which can be fitted to six emission peaks at 508 nm, 582 nm, 611 nm, 642 nm, 679 nm and 753 nm, respectively. The green emission peaks (507 nm and 508 nm) can be attributed to near band-edge emission of CdS, and the mechanism of other defect emissions is discussed.