Optical properties of ZnS nanowires synthesized via simple physical evaporation

Single-crystal ZnS nanowires were successfully synthesized in large quantities via simple thermal physical evaporation without any metallic catalyst. The microstructure and composition of ZnS nanowires were performed by transmission electron microscopy and high-resolution transmission electron microscopy. The Raman spectrum of wurtzite-2 H structure of ZnS nanowires showed the LO and TO mode: E1(LO)=A1(LO)=351cm-1, E1(TO)=A1(TO)=273cm-1. A new line at 338 cm−1 was found. We used the modified Bessel functions to describe the surface phonon mode of wire-structured materials originally. The theoretical result was in good agreement with the experimental data. Therefore the new line could be assigned to surface phonon mode. Furthermore, photoluminescence property of ZnS nanowires was also investigated: the green emission band around 515 nm could be attributed to S vacancies in ZnS.