Huang, Po-Shun
(2016)
Electrical and Optical Properties of Nanostructured Metal-Embedded ZnO Films for Transparent Conductors.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
The ability to enhance the carrier concentration without compromising the electron mobility is desired for ZnO-based transparent conducing oxide (TCO) materials, since the impurity doping for high carrier concentration increases the carrier scattering centers. Therefore, we demonstrated that ZnO-based films embedded with nanostructured metals can offer TCO composite films to possess a high carrier concentration without severely damaging the carrier mobility. Those unique properties of these nanocomposite films are attributed to the electron donation from nanostructured metal. Temperature-dependent Hall effect measurements reveal that electrons donated from metal nanoparticles could overcome the low Schottky barrier (or ohmic contact) at metal-ZnO interface and further transport in the ZnO matrix. Once electrons are transferred to the ZnO matrix, they can travel with less impurity-scattering. In addition, ZnO films embedded with a mixture of nanoparticles and nanowires have improved conductivity and optical transmission since electrons provided from nanoparticles or nanowires can transport in percolated conducting paths as long as the critical volume ratio of the metal constituent is achieved.
Furthermore, ZnO films embedded with earth-abundant Cu-Ni core-shell NPs exhibited conductivity which is increased by up to two-orders of magnitude than that of unintentionally doped ZnO film. These Cu-Ni core-shell NPs showed much more thermal stability than monometallic Cu NPs. It was reported that the conductivity of ZnO: Cu NP composite films degraded at 300 oC. In contrast, ZnO: Cu-Ni NP films maintained a good conductivity caused by the Cu-Ni core-shell NPs even after the heat treatment. This is due to the fact that the surface of Ni shell was oxidized preferentially and formed a uniform NiOX thin layer passivating Cu cores.
In the future, we expect to fabricate ZnO embedded Cu-Ni nanoparticles and nanowires annealed at a low temperature with a controlled volume ratio. Our goal is not only to improve the conductivity and transparency of such composite films but also provide an affordable choice of electrode materials for the application of solar cells.
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| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
26 January 2016 |
| Date Type: |
Publication |
| Defense Date: |
10 July 2015 |
| Approval Date: |
26 January 2016 |
| Submission Date: |
11 November 2015 |
| Access Restriction: |
2 year -- Restrict access to University of Pittsburgh for a period of 2 years. |
| Number of Pages: |
106 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Materials Science and Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
transparent conducting oxides (TCOs), Zinc Oxide (ZnO), metal nanoparticles, metal nanowires. |
| Date Deposited: |
26 Jan 2016 16:07 |
| Last Modified: |
26 Jan 2018 06:15 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/26321 |
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