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Winarski Final 05172019.pdf (12.59 MB)
ETD Abstract Container
Abstract Header
Development of zinc oxide based flexible electronics
Author Info
Winarski, David J
Permalink:
http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1558088851479794
Abstract Details
Year and Degree
2019, Doctor of Philosophy (Ph.D.), Bowling Green State University, Photochemical Sciences.
Abstract
This dissertation work is focused on development of zinc oxide (ZnO) thin films by atomic layer deposition (ALD) and sol-gel processes and investigating its optoelectronic properties and potential applications in flexible electronics. Through ALD efforts, a unique doping method was developed to incorporate In
3+
and Ga
3+
donors in ZnO at 250°C. The ALD process allowed us to deposit individual layers of In and Ga precursors, sandwiched between many layers of ZnO. The result is a 160-nm indiumgallium- doped ZnO (IGZO) transparent conductive oxide (TCO), with a sheet resistance of 60.9 Ω·sq
-1
and percent transmittance > 93.8% at 550 nm, and figure of merit
Φ
= 8.66 × 10
-3
Ω
-1
. IGZO is shown to be amorphous or polycrystalline in nature, depending on the substrate, but all IGZO thin films exhibit a low resistivity
ρ
(≤1.10 × 10
-3
Ω·cm), high carrier concentration
η
(≥2.30 × 10
20
cm
-3
), and high mobility
μ
(≥15.3 cm²/V·s). IGZO was found to be a fully degenerate semiconductor. Compared to gallium-doped ZnO (GZO), it appears that In
3+
is responsible for the improved polycrystalline growth and increased grain size. Based on these results IGZO is a promising replacement for the industry-standard indium tin oxide (ITO) for TCO applications. A sol-gel approach was used to deposit ZnO and IGZO layers onto a variety of flexible and transparent substrates using spin coating, inkjet printing (IJP), and aerosol jet printing (AJP) tools. In and Ga were introduced as co-dopants in solution and improved conductivity and polycrystalline growth. The polycrystallinity of ZnO improves with temperature from 200– 400°C and is dependent on the substrate. Both ZnO and IGZO thin films exhibit a decrease in resistivity upon UV exposure (10
3
–10
6
Ω·cm). Increasing the light intensity further shows a nonlinear behavior. This effect is attributed to UV light adsorption and oxygen desorption. Upon bending the substrate at a 4 mm radius of curvature, the photoconductive response is decreased by 10
4
Ω·cm and cannot be restored. A spin coating method was used to study the effects of In and Ga as individual dopants and co-dopants (0–3% in solution). Ga-doping gradually decreases the crystallite size
D
and polycrystallinity at doping levels up to 2%, due to Ga
3+
having a smaller ionic radius than Zn
2+
, which causes in the lattice. A further increase up to 3% shows a slight increase in
D
, but a less polycrystalline structure, suggesting that Ga interstitials are forming. In-doping is shown to increase
D
and polycrystallinity at a doping levels of 1%, while doping further to 3% hinders crystallinity. The increase in
D
is due to In
3+
having a larger ionic radius than Zn
2+
and the eventual loss in polycrystallinity is due to the stress induced by In. Sol-gel ZnO was used in prototyping of UV photodetectors and thin-film transistors (TFTs) with silver inks. AJP was used to deposit sol-gel ZnO and silver inks with a minimum line width of ~136 μm and ~109 μm, respectively. A minimum gap of ~65 μm was achieved between silver source and drain contacts. The photoconductive nature of ZnO is shown through time-resolved photocurrent measurements, while there were no TFT I-V characteristic observed.
Committee
Farida Selim, Ph. D. (Advisor)
Brent Archer, Ph. D. (Other)
Malcolm Forbes, Ph. D. (Committee Member)
Emily Heckman, Ph. D. (Committee Member)
Alexey Zayak, Ph. D. (Committee Member)
Pages
124 p.
Subject Headings
Physics
Keywords
zinc oxide
;
IGZO
;
degenerate semiconductor
;
flexible electronics
;
additive manufacturing
;
aerosol jet printing
;
inkjet printing
;
photoconductivity
Recommended Citations
Refworks
EndNote
RIS
Mendeley
Citations
Winarski, D. J. (2019).
Development of zinc oxide based flexible electronics
[Doctoral dissertation, Bowling Green State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1558088851479794
APA Style (7th edition)
Winarski, David.
Development of zinc oxide based flexible electronics.
2019. Bowling Green State University, Doctoral dissertation.
OhioLINK Electronic Theses and Dissertations Center
, http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1558088851479794.
MLA Style (8th edition)
Winarski, David. "Development of zinc oxide based flexible electronics." Doctoral dissertation, Bowling Green State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1558088851479794
Chicago Manual of Style (17th edition)
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Document number:
bgsu1558088851479794
Download Count:
512
Copyright Info
© 2019, all rights reserved.
This open access ETD is published by Bowling Green State University and OhioLINK.