Date of Award

12-4-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics and Astronomy

First Advisor

Tansel Karabacak

Abstract

Over recent years, great efforts are being dedicated to developing low cost and high-efficiency nanostructured design for optoelectronic applications. Nanostructured semiconductor materials have demonstrated superior performance as compared to bulk materials. Core/shell nanostructured geometries have received a great deal of attention not only in the area of synthesis and characterization but also in their potential applications. These structures have been used in abundance in various areas such as electronics, sensors, catalysis, biomedical, and optical devices. Well-controlled core/shell nanostructured geometries can offer a significant improvement in the devices' performance. Therefore, the fabrication of complex 3D core/shell architectures with controlled morphology, homogeneous and dimensionality has attracted much attention recently. At the same time, the demand for a novel and low-cost approach to fabricate promising core/shell structures increased. This dissertation presents design, fabrication, and test of a low-cost core/shell heterostructures for high efficiency photoconductive devices constructed based on CuO nanoleaves (NLs)-core/Cu-metal shell. In this work, copper (II) oxide (CuO), which is a p-type semiconductor, has been used as an absorber layer. CuO nanoleaf structures with different thickness and roughness were grown by a simple hot water treatment (HWT) technique without using any chemical additives on Cu sheets and ITO-coated glass substrate. Moreover, high-pressure sputtering (HIPS) technique was successfully utilized to form a uniform shell layer around nanoleaf structures. The prepared HWT-CuO/HIPS-metal (core/shell) heterostructures have been used to demonstrate photocurrent response enhancement in the radial interface contact. Also, the influence of the morphology and thickness/roughness of the absorber layer on the light trapping and carrier collection properties are investigated. For this study, the characterization techniques including scanning electron microscopy (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy and photocurrent dynamic response have been used. In addition, conventional CuO thin film (TF) samples were synthesized by thermal oxidation method and tested for comparison. Finally, a simulation study using finite difference time domain (FDTD) shows that introducing a 3D nanostructured geometry results in diffuse scattering of light and leads to high optical absorption.

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