Localized suppression of longitudinal-optical-phonon–exciton coupling in bent ZnO nanowires

Abstract

Using confocal micro-Raman and photoluminescence spectroscopy, we studied bending effects on optical properties of individual ZnO nanowires. Raman spectroscopy shows that local tensile strain can be introduced by bending the nanowire. The strain is expected to reduce the band gap on the bent part and modify the local phonon-exciton interaction. The corresponding micro-photoluminescence spectra indicate local suppression of the longitudinal-optical (LO) phonon-exciton interaction, which is determined by the intensity ratio of the second-order LO-phonon replica of the free exciton (FX-2LO) to the first-order process (FX-1LO). Our results may provide insight into the modulation of local electrical and optical properties by deforming the nanostructures.

SiO2 substrate and Mo,In codoping effect on crystalline and vibrational characteristics of ZnO sprayed thin films

“…5a are in agreement with several previous reports on the sensitivity of the LO phonon mode at defects [40,41], at residual stresses induced in the thin film/substrate interface [40,41], and at the surface states of thin films (roughness, grain characteristics and surface defects) [42,40,43]. The irregularity observed at In = 2% could be attributed to the experimental conditions of deposition in ambient atmosphere, which were difficult to respect for all samples, and to the SiO 2 substrate surface state (roughness, corrugation), which might have varied from sample to sample [34,44,45].…”

In-situ optical transmission electron microscope study of exciton phonon replicas in ZnO nanowires by cathodoluminescence

“…9 For those optical applications, the coupling between exciton and longitudinal optical phonon (LO) is an important issue. [10][11][12][13][14] The coupling is related to the crystal structure and defect concentration, and is affected by strain. [15][16][17][18][19] Here, we study the coupling effect by room temperature in-situ Transmission Electron Microscope (TEM) cathodoluminescence (CL).…”

Resonant exciton-phonon coupling in ZnO nanorods at room temperature

“…Strain in the bent NWs, as shown quite unconvincingly in a single NW while the phenomenon is in the larger scale, are made responsible for the observed coupling. 12 Similar argument of coupling of piezoelectric and semiconducting properties is also put forward in observing enhanced exciton-phonon coupling at low temperature for bent ZnO NWs. It has been known that point contact spectroscopy is a powerful method to obtain valuable information about the interactions of electrons with elementary excitations in various solids, such as phonons and magnons.…”

“…9,10 The observation of phonon-exciton interaction was mostly restricted to low temperature <150K for quantum dot structures. There are few reports 11,12 covering excitonic features in ZnO nanowires (NWs) at RT. These studies, however do not elaborate on the possible physical origin.…”