Optical property modification of ZnO: Effect of 1.2 MeV Ar irradiation

TL;DR

This study investigates how 1.2 MeV Ar ion irradiation affects the structural, optical, and electrical properties of ZnO, revealing defect formation, optical shifts, and resistivity changes with increasing irradiation fluence.

Contribution

It provides a detailed analysis of defect evolution and property modifications in ZnO due to high-energy ion irradiation, which is novel in understanding irradiation-induced defect dynamics.

Findings

ZnO retains its crystal structure up to high fluences.

Photoluminescence is quenched and then recovered with irradiation.

Resistivity decreases significantly at high fluence.

Abstract

We report a systematic study on 1.2 MeV Ar^8+ irradiated ZnO by x-ray diffraction (XRD), room temperature photoluminescence (PL) and ultraviolet-visible (UV-Vis) absorption measurements. ZnO retains its wurtzite crystal structure up to maximum fluence of 5 x 10^16 ions/cm^2. Even, the width of the XRD peaks changes little with irradiation. The UV-Vis absorption spectra of the samples, unirradiated and irradiated with lowest fluence (1 x 10^15 ions/cm^2), are nearly same. However, the PL emission is largely quenched for this irradiated sample. Red shift of the absorption edge has been noticed for higher fluence. It has been found that red shift is due to at least two defect centers. The PL emission is recovered for 5 x 10^15 ions/cm^2 fluence. The sample colour is changed to orange and then to dark brown with increasing irradiation fluence. Huge resistivity decrease is observed for the sample irradiated with 5 x 10^15 ions/cm^2 fluence. Results altogether indicate the evolution of stable oxygen vacancies and zinc interstitials as dominant defects for high fluence irradiation.