Chemomechanical Polishing Effects on the Room Temperature Photoluminescence of Bulk ZnO: Exciton-LO Phonon Interaction

Abstract

A study of the effects of chemomechanical polishing on the room temperature photoluminescence of both polar faces of ZnO single crystals is presented. A distinct peak which we associate with second order exciton-phonon (FX-2LO) emission and which dominates the LO emission for both (0001) and (000 1 1) etched surfaces is observed. Chemomechanical polishing results in reduction of the distinct FX-2LO peak, and an increase in the relative importance of first order exciton-phonon (FX-1LO) emission. We attribute this to disorder introduced by the polishing process.Introduction The recent availability of high crystalline quality bulk ZnO presents new possibilities for short wavelength light emitters. Chemomechanical polishing is typically used in substrate preparation prior to epitaxial growth for creating flat surfaces with minimum roughness and subsurface damage. In this work, we examined the effects of chemomechanical polishing on the room temperature (RT) photoluminescence (PL) of both polar faces of undoped ZnO single crystals.

Structural and optical properties of nanocrystalline ZnO thin films synthesized by the citrate precursor route

“…This asymmetry may be attributed to coupling of free excitons and longitudinal optical (LO) phonon replicas [26,27]. Each PL spectrum was deconvoluted using Gaussian approximations in MATLAB TM by varying the peak position and amplitude.…”

Pressure-dependent photoluminescence study of ZnO nanowires

“…[14][15][16][17][18] These results have led to the general belief that the broadband emission in green spectral region involves defects.…”

Effect of carrier gas species and flow rates on the properties of ZnO thin films prepared by chemical vapor deposition using zinc acetate dihydrate

“…The gas flow rates were both 1.0 L/min. no oxygen in the carrier gas, the NBE emission at 3.241 eV is known due to donor-bound exciton and its longitudinal optical phonon replica (DX-LO) [22]. As oxygen flow rate increases from 0 to 100 sccm, DX-1LO emission at 3.241 decreases, while emission peak centered at 3.137 eV becomes dominant.…”

“…The bandgap of ZnO is 3.37 eV and its exciton binding energy is 60 meV, which allows near-band-edge emission (NBE) emission to be dominated by free exciton and its longitudinal optical (LO) phonon replica at room temperature. Due to defects or impurity, room temperature NBE emission peak position may vary from UV to violet over a range of $100 meV [22,23]. Carbon and hydrogen are common impurities in ZnO prepared by sublimation of zinc acetate due to their presence in the precursor [24].…”