Date of Award

2016

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

Sub-Department

College of Arts and Sciences

First Advisor

Andrew B Greytak

Abstract

Semiconductor nanowires have been widely studied due to their unique properties such as width comparable to critical length-scales, high aspect ratio, and high carrier mobility. These unique properties make them a suitable candidate for various optical and electronic devices like photovoltaics, photodetectors, and field effect transistors. The nanowire surface plays an important role in the performance of these devices because of their high surface to volume ratio. The larger surface area of nanowires may provide better charge separation than planar heterostructures in photovoltaics by providing shorter distance to move for carrier before separation, however, presence of surface states may lead to the recombination of photo-generated carriers, limiting the amount of charge separation. In order to remove these surface states, ligands can be attached to the surface of nanowires.

In this work CdS and CdSe nanowires are grown through the high temperature Vapor-Liquid-Solid (VLS) process. VLS process yields single crystalline, low defect nanowires with controllable length and diameter. In order to show ligand binding on nanowire surface, CdS nanowires were treated with a dye-labeled polymer. Fluorescence microscopy and spectroscopy were used to confirm ligand binding. Fluorescence microscopy can also be used to show the kinetics of ligand binding on nanowire surfaces. In order to control the electronic properties of the nanowire surfaces, nanowires were treated with solution phase and vapor phase reagents.

Photoluminescence measurements and transport measurements were performed before and after the chemical treatment to see the consequences of ligand binding on the optical and electronic properties of nanowires.

Rights

© 2016, Pravin Paudel

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