Nanophotonics Laboratory, Department of Physics, National Institute of Technology, Tiruchirappalli-620 015, India.
Nanoscale. 2019 Mar 14;11(11):4948-4958. doi: 10.1039/c8nr07988a.
In the present study, different morphologies of ZnS nanostructures have been synthesized through a hydrothermal method and their Raman spectral modes are investigated. Raman scattering from surface optical (SO) modes has been seen and identified as a strange shoulder band of LO at 340 cm-1 in nanowires (NWs) with a hexagonal wurtzite structure of ZnS in air medium. X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques have been used to confirm the hexagonal phase and the modulation in the surface during the growth process, which causes the translational symmetry breaking to activate the SO mode. The appearance of a strong SO mode in NWs has been obviously confirmed by the frequency downshift of the SO mode in different dielectric media with dielectric constants ranging from 1 to 2.56. The SO phonon mode shift due to the roughness in the NW faces has been estimated from the wave-vector that activates the SO mode and an approximate dielectric continuum (DC) model has been used to understand the SO modes in NWs. The surface perturbation responsible for the activation of the SO mode has been estimated and is compared with the surface modulation along the growth axis of the NW from the TEM images.
在本研究中，通过水热法合成了不同形态的 ZnS 纳米结构，并研究了它们的拉曼光谱模式。在空气中具有六方纤锌矿结构的 ZnS 纳米线 (NWs) 中，观察到并识别出表面光学 (SO) 模式的拉曼散射，其表现为 LO 在 340 cm-1 处的奇异肩带。X 射线衍射 (XRD) 和透射电子显微镜 (TEM) 技术用于确认六方相和生长过程中表面的调制，这导致平移对称性被打破，从而激活 SO 模式。在不同介电常数为 1 到 2.56 的介电介质中，SO 模式的频率下移明显证实了 NWs 中存在强 SO 模式。由于 NW 表面的粗糙度引起的 SO 声子模式位移，已经从激活 SO 模式的波矢进行了估计，并且已经使用近似的连续介电 (DC) 模型来理解 NWs 中的 SO 模式。已经估计了对 SO 模式激活负责的表面微扰，并与 TEM 图像中 NW 生长轴上的表面调制进行了比较。
