Development of zinc oxide based flexible electronics

Bibliographic Details
Main Author:	Winarski, David J.
Language:	English
Published:	Bowling Green State University / OhioLINK 2019
Subjects:	Physics zinc oxide IGZO degenerate semiconductor flexible electronics additive manufacturing aerosol jet printing inkjet printing photoconductivity
Online Access:	http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1558088851479794

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spelling	ndltd-OhioLink-oai-etd.ohiolink.edu-bgsu15580888514797942021-08-03T07:11:12Z Development of zinc oxide based flexible electronics Winarski, David J. Physics zinc oxide IGZO degenerate semiconductor flexible electronics additive manufacturing aerosol jet printing inkjet printing photoconductivity This dissertation work is focused on development of zinc oxide (ZnO) thin films byatomic layer deposition (ALD) and sol-gel processes and investigating its optoelectronicproperties and potential applications in flexible electronics.Through ALD efforts, a unique doping method was developed to incorporate In<sup>3+</sup> andGa<sup>3+</sup> donors in ZnO at 250°C. The ALD process allowed us to deposit individual layers of In andGa 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 60.9Ω·sq<sup>-1</sup> and percent transmittance > 93.8% at 550 nm, and figure of merit <I>Φ</I> = 8.66 × 10<sup>-3</sup> Ω<sup>-1</sup>.IGZO is shown to be amorphous or polycrystalline in nature, depending on the substrate, but allIGZO thin films exhibit a low resistivity <I>ρ</I> (≤1.10 × 10<sup>-3</sup> Ω·cm), high carrier concentration <I>η</I>(≥2.30 × 10<sup>20</sup> cm<sup>-3</sup>), and high mobility <I>μ</I> (≥15.3 cm²/V·s). IGZO was found to be a fullydegenerate semiconductor. Compared to gallium-doped ZnO (GZO), it appears that In<sup>3+</sup> isresponsible for the improved polycrystalline growth and increased grain size. Based on theseresults IGZO is a promising replacement for the industry-standard indium tin oxide (ITO) forTCO applications.A sol-gel approach was used to deposit ZnO and IGZO layers onto a variety of flexibleand 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 andpolycrystalline 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 inresistivity upon UV exposure (10<sup>3</sup>–10<sup>6</sup> Ω·cm). Increasing the light intensity further shows anonlinear behavior. This effect is attributed to UV light adsorption and oxygen desorption. Uponbending the substrate at a 4 mm radius of curvature, the photoconductive response is decreasedby 10<sup>4</sup> Ω·cm and cannot be restored.A spin coating method was used to study the effects of In and Ga as individual dopantsand co-dopants (0–3% in solution). Ga-doping gradually decreases the crystallite size <I>D</I> andpolycrystallinity at doping levels up to 2%, due to Ga<sup>3+</sup> having a smaller ionic radius than Zn<sup>2+</sup>,which causes in the lattice. A further increase up to 3% shows a slight increase in <I>D</I>, but a lesspolycrystalline structure, suggesting that Ga interstitials are forming. In-doping is shown toincrease <I>D</I> and polycrystallinity at a doping levels of 1%, while doping further to 3% hinderscrystallinity. The increase in <I>D</I> is due to In<sup>3+</sup> having a larger ionic radius than Zn<sup>2+</sup> and theeventual 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 minimumline width of ~136 μm and ~109 μm, respectively. A minimum gap of ~65 μm was achievedbetween silver source and drain contacts. The photoconductive nature of ZnO is shown throughtime-resolved photocurrent measurements, while there were no TFT I-V characteristic observed. 2019-08-06 English text Bowling Green State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1558088851479794 http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1558088851479794 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection	NDLTD
language	English
sources	NDLTD
topic	Physics zinc oxide IGZO degenerate semiconductor flexible electronics additive manufacturing aerosol jet printing inkjet printing photoconductivity
spellingShingle	Physics zinc oxide IGZO degenerate semiconductor flexible electronics additive manufacturing aerosol jet printing inkjet printing photoconductivity Winarski, David J. Development of zinc oxide based flexible electronics
author	Winarski, David J.
author_facet	Winarski, David J.
author_sort	Winarski, David J.
title	Development of zinc oxide based flexible electronics
title_short	Development of zinc oxide based flexible electronics
title_full	Development of zinc oxide based flexible electronics
title_fullStr	Development of zinc oxide based flexible electronics
title_full_unstemmed	Development of zinc oxide based flexible electronics
title_sort	development of zinc oxide based flexible electronics
publisher	Bowling Green State University / OhioLINK
publishDate	2019
url	http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1558088851479794
work_keys_str_mv	AT winarskidavidj developmentofzincoxidebasedflexibleelectronics
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Development of zinc oxide based flexible electronics

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