Zinc oxide (ZnO) is a II–VI compound semiconductor with a wide direct band-gap of
3.3 eV and a hexagonal structure. ZnO is often used in the paint, paper, rubber, food
and drug industries. It is also a promising material in nanotechnology applications, for
example in nano-electronics and nano-robotic technology. With its wide band-gap, high
exciton binding energy and high breakdown strength, ZnO can be utilized for electronic
and photonic devices, as well as for high-frequency applications. To produce such
optoelectronic devices, control of electronic properties, such as the nature of conduction
and carrier density, is required. However, such control has proved difficult for ZnO.
Much research has been done to pursue p type ZnO using different processing
techniques, however, there are few reports addressing the relationships of
microstructure on optical and electrical properties, ion implantation doping of ZnO and
nano-ZnO polymer composites.
The objectives of this project are to study the processing, composition, microstructure,
electronic, optical, UV and electromagnetic shielding properties of ZnO thin films and
composites; to explore ion implantation as a method to dope Al, Ag, Sb, Sn and TiN
into ZnO thin films or single crystals; to develop conducting, transparent oxide films
and/or p-type semiconductor for potential device applications; and to study the
relationships of doping, microstructure and electro-optical properties of ZnO thin films
and nano-ZnO polymer composites.
The experimental work included annealing, characterizing and implantation of
magnetron sputtering ZnO thins films and ZnO single crystals. Ion implantation was
employed to dope ZnO thin films or single crystals with Ti, N, Sb, Al, Sn and Ag. The
diffusion behaviour of implanted and annealed ZnO and the ellipsometry of implanted
ZnO thin films were investigated. The relationship of microstructure and properties of
as-deposited, annealed and implanted ZnO was studied. The results show that compared
to direct current (d.c.) sputtering, the films produced using radio frequency (r.f.) have
significantly lower resistivity, porosity and stress. The residual stress can change the
band gap of ZnO thin films. Conductivity experiments suggest that the conduction
mechanism of sputtered ZnO thin films involves charge transport in the conduction
band and electronic hopping between the nearest neighbour donor levels. Furthermore,
the optical transmission of ZnO thin films is high in the visible, with excellent UV
absorption properties. It is also found that annealing alters the grain size and
composition, and reduces the stress of ZnO thin films. Moreover, ion implantation
causes partial amorphousness of ZnO films in the implantation zone and introduces
stress and interstitial dopants. Transport of Ions in Matter (TRIM) modelling and
Secondary Ion Mass Spectrometer (SIMS) analysis confirm that lighter elements
implant deeper than heavy elements. The implanted ZnO shows some p type tendency
and evidence of photoluminescence. Lastly, the nano-ZnO and polymer composites
show excellent mechanical, good UV barrier properties.
| Identifer | oai:union.ndltd.org:AUCKLAND/oai:researchspace.auckland.ac.nz:2292/2136 |
| Date | January 2006 |
| Creators | Lee, Jim, 1963- |
| Contributors | Professor Debes Bhattacharyya, Professor Jim Metson |
| Publisher | ResearchSpace@Auckland |
| Source Sets | University of Auckland |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Scanned from print thesis |
| Rights | Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated., https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm, Copyright: The author |
| Relation | PhD Thesis - University of Auckland, UoA1698376 |
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