Title

Defects in Zinc Oxide Nanocrystals Studied by Photoluminescence and Raman Spectroscopy

Document Type

Student Presentation

Presentation Date

4-16-2018

College

College of Arts and Sciences

Department

Physics

Faculty Sponsor

Dmitri Tenne

Abstract

Zinc oxide (ZnO) is a direct, wide bandgap semiconductor material with many promising properties for blue/ultraviolet optoelectronics, transparent electronics, spintronic devices, sensor applications and various biomedical applications. ZnO nanocrystals of varied sizes were studied for this project using cold temperature photoluminescence (PL) and Raman spectroscopy. The ZnO nanocrystal samples were synthesized using the forced hydrolysis of zinc acetate dihydrate, where various amounts of nanopure water were added to control the size of the nanoparticles. Portions of each sample were annealed in air or nitrogen atmosphere at various temperatures from 350-550°C. The samples were then characterized by x-ray diffraction, transmission electron microscopy, confocal optical microscopy, and x-ray photoelectron spectroscopy. Ultraviolet light of a helium-cadmium laser (325 nm) was used for excitation of Raman and PL spectra measured at 10 K. The spectra of samples subject to variable synthesis parameters (nanocrystal size, annealing temperature and atmosphere, surfractant/surface capping agent) showed that defects leading to the appearance of visible PL bands can be introduced in the nanocrystals in a controllable way. Raman spectra show the appearance of a defect-related band which correlates with the corresponding PL spectra. The appearance of visible light emission from the ZnO nanocrystals has potential for biomedical and optoelectronic applications.

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