Tunable ultraviolet sensing performance of Al-modified ZnO nanoparticles

Abstract

The potential of polycrystalline Al-doped ZnO nanoparticles as an active material for UV photodetectors has been investigated. The Rietveld refinement of powder X-ray diffraction data revealed a single hexagonal phase of the nanoparticles. A slight deviation in the lattice cell constants from pristine ZnO was observed, associated with defect creation and strain generated due to Al3+ substitution. High-resolution transmission electron microscopy image reveals a spherical morphology of both the doped and undoped ZnO nanoparticles. Stacking faults observed in the Al-doped samples is an indication of a proper Al-doping and is a signature of high density of crystal defects. The bandgap was found to reduce due to the delocalization of impurity energy states as a result of Al3+ substitution. Consequently, conductivity was improved in doped samples. Photoluminescence spectroscopy revealed a strong dependence of the emissions from defect sites on dopant content. Further, a correlation of the FWHM of the E2high Raman mode to the Urbach energy was observed. The UV sensing analysis demonstrates the enhancement of the photocurrent and improved sensitivity. Thus, this work provides a simple, cost-effective, and tunable processing strategy for synthesizing and applying ZnO-based nanomaterials for high-performance UV photodetectors.