Synthesis ZnO Transparent Conductive Oxide by Electrospray Deposition
Date
2015-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
New York State College of Ceramics at Alfred University. Kazuo Inamori School of Engineering.
Abstract
The objective of this thesis was to synthesize ZnO-based transparent oxide (TCO) thin
film by using an economically-versatile fabrication technique called electrospray deposition
(ESD). A co-doping approach was employed to enhance optoelectronic properties of undoped
ZnO, which is a non-toxic and abundant material for flat display panels and energy-harvesting
applications.
Firstly, ESD process parameters were investigated in order to optimize the quality of thin
film, namely, deionized water content in precursor, applied voltage, deposition temperature, flow
rate, deposit distance, and deposit time. Regression plots revealed the tendency of individual
process parameter towards % film coverage area. In addition, the factorial design of the
experiment was performed to determine significant process parameters (P-value < 0.05), which
showed a strong influence to film quality at R2 of 87.61%.
Secondly, 0-3%wt of Aluminum (Al) concentration were co-doped with 3%wt of Lithium
(Li). The aim was to synthesize p-type ZnO-based TCO by a co-doping approach. Li (acceptor)
and Al (donor) at different ratios of acceptor-to-donor (A/D) were investigated effects on defect
diffusion mechanism, film’s crystallinity, microstructure, and topography by X-ray diffraction
(XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Hall effect
measurement and UV-Visible spectrometer studies were carried out to evaluate optoelectronic
properties of as-annealed film. The lowest resistivity of 2.51x10-3 Ohm∙cm of p-type ZnO-based
TCO was obtained without optical properties degradation by employing A/D of 2:1 due to the
scattering effect of ionized defect and was minimized by A-D-A defect cluster.
Lastly, 3%wt of gallium (donor) and 3%wt of lithium (acceptor) were co-doped with 0-
3%wt of Aluminum concentration in order to compare effects of co-dopant types on defect
diffusion mechanism. A small variation of lattice distortion as %Al increased, which suggested
that dopant solubility was improved by substitutional mechanism. As a result, the film’s
crystallinity and microstructure were improved due to the minimization of disturbing stress and
enhanced diffusibility. Consequently, UV-Visible spectrometer and 4-point probe measurement
showed that optoelectronic properties of the film improved in co-doped samples.
Description
Advisory committee members: S.K. Sundaram, Nathan Mellot. Dissertation completed in partial fulfillment of the requirements for the degree of Masters of Science in Ceramic Engineering at the Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred University
Type
Thesis