Cathodoluminescence study of e‐irradiated and plastically deformed ZnO crystals

Abstract

Intrinsic defects are generated by e‐irrradiation, and plastic deformation in ZnO crystals. Spectrally resolved cathodoluminescence (CL) experiments permit the analysis of the optical signature of those defects. We present herein a CL analysis of ZnO crystals irradiated with high energy electrons, and plastically deformed by Vickers indentation. Spectral changes around 3.3 eV and in the deep level emission are observed in the irradiated samples. These changes are compared to those observed around the extended defects introduced by Vickers indentation, which present a similar signature to the e‐irradiated samples, suggesting relation between the defects generated by plastic deformation and e‐irradiation. Zn vacancies seem to be the dominant defects generated in both processes (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Characterization of polishing induced defects and hydrofluoric acid passivation effect in ZnO

“…1(a) demonstrates that mechanical polishing creates high concentrations of V Zn -related defects within the outer $500 nm. This is consistent with recent PL 15 and PAS 19 measurements of mechanically polished ZnO, which showed the formation of vacancy type defects in the near surface region including V Zn . Previous CL and PL of ZnO showed that mechanical polishing leads to subsurface damage with NBE intensity decreases, 10,14,15 which our results confirm.…”

“…This is consistent with recent PL 15 and PAS 19 measurements of mechanically polished ZnO, which showed the formation of vacancy type defects in the near surface region including V Zn . Previous CL and PL of ZnO showed that mechanical polishing leads to subsurface damage with NBE intensity decreases, 10,14,15 which our results confirm. The $2.05 eV emissions apparent for maximum range depths of $500 nm are also consistent with the depletion region measured by C-V previously of nearly 600 nm and with the acceptor nature of V Zn -related defects, which compensate the n-type doping.…”

“…20 Both CL and PL research on ZnO demonstrated that mechanical polishing leads to surface and near surface damage, which decreases near band edge (NBE) luminescence efficiency, and forms non-radiative recombination centers (NRRCs) and intrinsic defects such as zinc vacancy (V Zn ) and zinc interstitial (Zn i ). [10][11][12][13][14][15][16][17] PAS studies also show creation of dislocations and vacancy defects in the near and sub-surface region after polishing. 19 Recent DLTS measurements show that mechanical polishing introduced two defect levels at 1.0 and 1.2 eV below the conduction band edge E C whose densities subsequent hydrofluoric acid (HF) etching reduced substantially while restoring bulk carrier densities.…”

“…Previous research also showed the soft nature of ZnO, [8][9][10] which significantly affects the wafer handling, processing, and manufacture of ZnO-based devices. Polishing induced damage has been investigated by cathodoluminescence (CL), [9][10][11][12][13][14][15] photoluminescence (PL), 16,17 ion channeling, 18 positron annihilation spectroscopy (PAS), 19 and deep level transient spectroscopy (DLTS). 20 Both CL and PL research on ZnO demonstrated that mechanical polishing leads to surface and near surface damage, which decreases near band edge (NBE) luminescence efficiency, and forms non-radiative recombination centers (NRRCs) and intrinsic defects such as zinc vacancy (V Zn ) and zinc interstitial (Zn i ).…”

Effect of laser polarization and crystalline orientation on ZnO surface nanostructuring in the regime of high-density electronic excitation

“…The accumulation of space charges might also be favorable in these directions. A relation between defects generated by electron irradiation and plastic deformation in ZnO crystals has been suggested [18]. Since localized charges in solids are closely related to excitons, cathodoluminescence microscopy of the nanostructured ZnO crystals could verify this hypothesis.…”