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.

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Typical morphology substrates can improve the efficiency of surface-enhanced Raman scattering; the need for SERS substrates of controlled morphology requires an extensive study. In this paper, one-dimensional ZnS:Al nanostructures with the width of approximately 300 nm and the length of tens um, and micro-scale structures with the width of several um and the length of tens um were synthesized via thermal evaporation on Au-coated silicon substrates and were used to study their size effects on Raman scattering and photoluminescent spectra. The photoluminescence spectra reveal the strongest green emission at a 5 at% Al source, which originates from the Al-dopant emission. The Raman spectra reveal that the size and morphology of the ZnS:Al nanowires greatly influences the Raman scattering, whereas the Al-dopant concentration has a lesser effect on the Raman scattering. The observed Raman scattering intensity of the saw-like ZnS:Al nanowires with the width of tens nm was eight times larger than that of the bulk sample. The enhanced Raman scattering can be regarded as multiple scattering and weak exciton—phonon coupling. The branched one-dimensional nanostructure can be used as an ideal substrate to enhance Raman scattering.

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