Exciton-phonon coupling in individual ZnTe nanorods studied by resonant Raman spectroscopy

Abstract

The exciton-phonon coupling in high-quality cubic phase zinc telluride (ZnTe) nanorods (NRs) is investigated by resonant micro-Raman spectroscopy near the direct bandgap of ZnTe. The scattering cross section of longitudinal optical (LO) phonon is enhanced significantly in the resonant process, where the enhancement factor of LO modes is much higher than that of the transverse optical (TO) modes, indicating a dominant Fröhlich electron-phonon interaction mechanism. Up to fifth-order LO phonons are observed by resonant Raman scattering at room temperature. The Huang-Rhys factor of individual NRs-and thus the exciton-LO coupling strengths-is evaluated, showing increasing with the NR diameter. Surface optical (SO) phonon and its high-order overtones are observed between nLO and (n − 1)LO + TO for the first time, whose positions are consistent with a dielectric continuum model. Strong acoustic phonon-exciton coupling induces a high-frequency shoulder above each nLO peaks with two maxima located around 14 cm −1 and 32 cm −1 , which are assigned to transverse acoustic and longitudinal acoustic phonons, respectively. The resonant multiphonon scattering process involving acoustic and LO phonons is discussed based on an exciton-intermediated cascade model, where a scattering sequence of acoustic phonon followed by LO phonons is favorable. These results advance the understanding of electron-phonon coupling and exciton scattering in quasi-one-dimensional systems, especially in the scarcely documented ZnTe compound, facilitating the development and optimization of NR-based optoelectronic devices.

Growth and characterisation of n- and p-type ZnTe thin films for applications in electronic devices

“…Two other peaks at ~120 cm -1 and ~142 cm -1 were also observed below the 1TO Raman phonon peak. These peaks arise as a result of elemental Te or presence of Te-rich phases in the material [29]. Similar peaks at low frequency ~122 cm -1 and ~141 cm -1 have also been seen in other II-VI binary compounds containing Te such as CdTe [32].…”

Raman Spectroscopy of Two-Dimensional Bi2TexSe3 − x Platelets Produced by Solvothermal Method

“…A prominent vibrational mode at 115 cm −1 is also observed in Bi 2 Te 3 , as shown in Figure 6c. According to previous report on bismuth chalcogenide nanoplates [31,32], this new peak of Bi 2 Te 3 are likely originated from Te impurities because laser can cause Te-containing compound to decompose and lead to strong Te Raman features.…”

Guided Growth of Horizontal p-Type ZnTe Nanowires

“…The PL spectra of guided nanowires grown on annealed M-plane is consistent with previous optical characterizations done on ZnTe nanostructures. 41,42 The maximum emission at 547 nm represents a small blue shift of 2 nm with respect to the 549 nm for bulk ZnTe. This slight blue shift may be attributed to compressive strain induced in the nanowires, or to a change in the dielectric constant of the substrate with respect to vacuum.…”