Size Effects of Raman and Photoluminescence Spectra of CdS Nanobelts

Abstract

Different sizes of CdS nanobelts were synthesized at 800, 850, and 900 °C by the thermal evaporation of CdS powders on Au-coated silicon substrates and were used to study the size effects of Raman scattering and photoluminescent spectra. The Raman spectra of CdS nanobelts clearly exhibit firstand second-order longitudinal optical (LO) Raman peaks, surface phonon peaks, and multiphonon processes when excited using a wavelength of 532 nm. The mechanism of exciton−phonon coupling was observed to be mainly associated with the Froḧlich interaction, and the coupling strength of the exciton−phonon increases with increasing lateral size. Compared with a larger CdS nanobelt, a narrower nanobelt exhibits a larger tensile strain. Recombination of free excitons (FX), excitons bound to neutral impurities (A 0 X), and donor−acceptor pairs (DAP) were identified from a low-temperature PL spectrum. At temperatures below ∼123 K, a red shift of the FX energy occurs with decreasing lateral size due to a larger uniaxial tensile strain; at temperatures above ∼123 K, a red shift of the FX energy occurs with increasing lateral size because of the reabsorption of the emitted light inside the thicker belt, indicating that the FX energy is affected by both the tensile strain and the surface-depletion-induced quantum confinement (the reabsorption of the emitted light) in the nanobelt.

Vertically aligned TiO2/(CdS, CdTe, CdSTe) core/shell nanowire array for photoelectrochemical hydrogen generation

“…By the way, the TiO 2 /CdTe sample shows the LO and TO Raman peaks at 164 and 138 cm À1 , with a small red shift compared to the reported bulk CdTe (169 and 141 cm À1 of LO and TO for bulk CdTe, respectively). The red shift of the Raman peaks compared with that of bulk CdTe was considered to be due to the effect of phonon confinement [47]. And the peak at 121 cm À1 could be contributed to the tellurium precipitates in CdTe crystals, which is consistent with the previous reports [48,49].…”

Rare earths (Ce, Eu) molar concentration-dependent of the structural and optical properties of CBD-CdS nanofilms

“…In addition, to the 1LO phonon and its phononic replicas for M65 sample, several vibrational bands are resolved at 219, 260 and 352 cm −1 suggesting that the samples have better crystalline quality [25]. The vibrational bands can be assigned to multiphonon scattering, which is consistent with reported works [26,27]. The feature at the high-energy shoulder, which is very weak peak at 352 cm −1 , which is the subject of a recent study by Dzhagan et al [28], who suggest that it results from the participation of acoustic phonons to the scattering process and the mode corresponding to the low-energy shoulder originates from surface optical FIGURE 7.…”

Facile method to prepare CdS nanostructure based on the CdTe films

“…The Raman peak located at 165 cm -1 corresponds to the LO mode of the CdTe film[41], and that located at 124, 103, 140 cm -1 correspond to the A1 (Te), LO-TA (CdTe) mode, E (Te)/TO (CdTe) mode[42], respectively. The Raman peak (300.5, 603.9 cm -1 ) corresponds to the LO, 2LO mode of CdS, and located at ~212.1 cm -1 can be assigned to CdS multi-phonon scatting, which is consistent with other reports[43][44][45]. There are two kinds of component in the film using 633 nm as the excitation wavelength.…”