Cathodoluminescence degradation study of the green luminescence of ZnO nanorods

Abstract

Bright green luminescence at 500 nm was obtained from chemical bath deposited ZnO nanorods after annealing in a reducing atmosphere (H2/Ar) at 700 °C for 30 min. Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and secondary electron microscopy (SEM) were used to study the effect of electron beam irradiation on the cathodoluminescence (CL) and the surface state of the sample. The CL intensity was monitored concurrently with the Auger peak-to-peak heights (APPHs) using the same electron beam for both techniques. CL intensity degradation was studied in vacuum and in an oxygen ambient. According to the AES spectra, all the principal elements (zinc and oxygen) were detected as well as carbon, which was removed at the initial stage of electron beam irradiation. No chemical change was observed during electron beam irradiation. In vacuum, the CL intensity decreased to almost half of its initial intensity after 100 C/cm2 electron dose and then stabilized. In the oxygen atmosphere, the CL intensity also decreased initially up to a dose of ~10 C/cm2 and thereafter recovered to about 90% of its original intensity and stabilized after a dose of ~100 C/cm2. No difference in the chemical state of Zn was observed with XPS for the original sample and the degraded ones. Only a small change in the defect contribution part of the O peak was observed. SEM images for the original and degraded samples showed that the electron beam irradiation induced surface changes in the morphology of the ZnO nanorods. Generally, the CL intensity was very stable under electron beam irradiation, suggesting that the material may be suitable for application in optoelectronics devices.