Probing the exciton-phonon coupling strengths of O-polar and Zn-polar ZnO wafer using hard X-ray excited optical luminescence

Abstract

The temperature-dependent hard X-ray excited optical luminescence (XEOL) spectroscopy was used to study the optical properties of O and Zn polarity of a c-plane single crystal ZnO wafer. By analyzing the XEOL and XRD, we found an unprecedented blue shift of the free exciton transition with increasing the excited carrier density as tuning the X-ray energy across the Zn K-edge, and the O-polar face possesses better crystal structure than the Zn-polar one. This spectral blue shift is attributed to the Coulomb screening of the spontaneous polarization by the excited free carriers that result in decreasing the exciton-phonon Fröhlich interaction to reduce exciton binding energy.

Probing size-dependent defects in zinc oxide using synchrotron techniques: impact on photocatalytic efficiency

“…Later, it resulted in a slight blue shift (∼30 meV) due to weakening of the exciton–phonon interaction. 62 However, no such peak shift was observed in N-ZnO which is possibly due to the small size of the N-ZnO making self-absorption less probable within the sample. 62,63 In addition to this, a drop in the branching ratio was initially observed, followed by leveling at a constant value, as shown in Fig.…”

X-ray Luminescent Properties of Zinc Oxide Films on the Sapphire M and A-Plane

“…Radiation-resistant scintillation materials based on oxides can be used as promising detectors of different radiation types. From the point of view of primary components availability and achievement of high scintillation characteristics of detector the ZnO-based structures are often considered as the most promising [1,2]. ZnO is characterized by the presence of edge (380−400 nm, with a typical deexcitation time of less than 1 ns [3]) and green defect (maximum in the region of 450−650 nm, typical deexcitation time is about 1 µs [4]) components of luminescence.…”

Investigation of Cavity Enhanced XEOL of a Single ZnO Microrod by Using Multifunctional Hard X-ray Nanoprobe

“…However, it is still rare to probe in the hard X-ray energy (multi-keV) range to characterize the optical properties of a single ZnO microrod with high spatial resoliution. Based on the advantage of using synchrotron source with continuous and tunable X-ray energy, we have used unfocused hard X-ray excited optical luminescence (XEOL) with X-ray energy set across the Zn K-edge and observed peculiar near-band-edge (NBE) emission from polar 13 and non-polar 14 ZnO wafers. The XEOL spectroscopy has been reported completely by Sham et al .…”