Raman selection rule for surface optical phonons in ZnS nanobelts

Abstract

We report Raman scattering results for high-quality wurtzite ZnS nanobelts (NBs) grown by chemical vapor deposition. In the Raman spectrum, the ensembles of ZnS NBs exhibit first order phonon modes at 274 cm(-1) and 350 cm(-1), corresponding to A1/E1 transverse optical and A1/E1 longitudinal optical phonons, in addition to a strong surface optical (SO) phonon mode at 329 cm(-1). The existence of the SO band is confirmed by its shift with different surrounding dielectric media. Polarization dependent Raman spectra were recorded on a single ZnS NB and for the first time a SO phonon band has been detected on a single nanobelt. Different selection rules for the SO phonon mode are shown from their corresponding E1/A1 phonon modes, and were attributed to the breaking of anisotropic translational symmetry on the NB surface.

Interface phonon modes in the [AlN/GaN]20 and [Al0.35Ga0.65N/Al0.55Ga0.45N]20 2D multi-quantum well structures

“…[23][24][25] Therefore, the nanomaterials such as 1D nanowires, 2D MQWs and SLs with a large surface area contribute significantly towards the SO or IF phonon signal as compared to that for the bulk crystals. 26 It was well established that the SO phonon mode frequency depends on the dielectric constant of the surrounding medium ( m ), as well as the shape, interfaces, saw tooth edges, periodicity of surface defects, diameter modulation and variation of density of the nanostructures.…”

“…[12][13][14][15][16][17][18][19][20][21][22] The periodic surface modulation and interfaces of the SL structures of 2D MQWs (ESI Figs. S1 and S2) may lead to the relaxation of Raman selection rules because of the breakdown of translational symmetry of the surface potential, 12,26 and it is anticipated that the unidentified Raman modes observed in the recorded spectra from the MQWs belong to the above mentioned IF(A 1 ) and IF(E 1 ) phonon modes, respectively. The surface layers of 9…”

“…and (LO) q=0 Raman modes with increasing  m value because of the change in the surrounding medium can be considered as a further confirmation for the presence of IF mode. [12][13][14][15][16][17][18][19][20][21][22]26 We also studied the temperature dependent evolution of IF phonon modes along with the allowed Raman modes of MQW structures (ESI Fig. S4).…”

“…[23][24][25] Therefore, the nanomaterials such as 1D nanowires, 2D MQWs and SLs with a large surface area contribute significantly towards the SO or IF phonon signal as compared to that for the bulk crystals. 26 It was well established that the SO phonon mode frequency depends on the dielectric constant of the surrounding medium ( m ), as well as the shape, interfaces, saw tooth edges, periodicity of surface defects, diameter modulation and variation of density of the nanostructures. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] In the present study, we investigated the behavior of IF phonon modes in the Raman spectra of were carried out with the help of plasma assisted molecular beam epitaxy (PAMBE).…”

Local structural studies on Co doped ZnS nanowires by synchrotron X-ray atomic pair distribution function and micro-Raman shift

“…Nanostructure materials with a large surface to volume ratio and local surface modulation lead to the observation of an extraordinary phonon mode known as the surface optical (SO) phonon mode, which is not observed for their bulk counterparts. 33 Recently, longitudinal-optical-phonon and plasmon coupling (LOPC) were investigated using Raman scattering to characterize the hole as well as electron concentrations in GaMnAs and Cl-ZnSe, respectively. 34,35 The strong interaction between LO phonons and collective excitation plasmons via their associated macroscopic electric elds has also been extensively studied in other compound semiconductors, such as SiC, GaAs, and GaN.…”