The optical properties of zinc oxide crystals and thin films prepared by different
methods are investigated.
Single crystal zinc oxide samples prepared by melt and hydrothermal growth
techniques were obtained. The influence of polarity and growth method on the
optical properties were studied and correlated with their electronic properties.
Thin films prepared by molecular beam epitaxy (MBE) and sputtering were
studied and the influence of growth conditions and post growth treatment on the
optical properties of the films was investigated.
The photo-luminescence (PL) of bulk zinc oxide was examined at high
resolution. Line widths of less than 0.1 meV were observed. More than a dozen
different transitions in the near band edge region (NBE 360-380 nm) were
noted, several of which displayed a separation of <0.5 meV which goes some
way to illustrating the complexity of the system. Attempts were made, with
some success, to reconcile the two main competing identification systems of the
NBE transitions and explanations for some of the discrepancies are provided.
The controversial deep level transitions in the visible part of the spectrum are fit
with 3 Gaussians and their identities discussed with relation to the available
literature. The presence of copper impurities was detected in annealed films and
a model to explain their behaviour under annealing conditions is hypothesised.
Films grown by MBE here at the University of Canterbury are shown to have
PL line widths of as little as 2.2 meV, the ratio of active oxygen species in the
growth chamber during deposition is shown to effect the optical quality of the
films. It is shown that annealing can improve the optical quality of the films and
various other methods of influencing the films properties are discussed.
Reactive, magnetron, direct current sputtering is shown to be the optimal
method of growth for maximising both optical and piezo-electric properties. Optimum annealing temperatures were found at 900 and 1100 ℃ with a local
minimum at 1000 ℃. X-ray diffraction, atomic force and scanning electron
microscopy measurements in addition to optical PL measurements show the
influence of annealing on the polycrystalline sputtered ZnO films. Films grown
on glass, silicon, sapphire and quartz were shown to display similar behaviour
under annealing conditions. It was found that zinc oxide based devices were
liable to be chemically unstable at temperatures above 1100 ℃.
The piezo electric properties of the films were examined and attempts were
made to prepare a zinc oxide film optimised for both optical quality and piezoelectric
properties for possible future applications of a hybrid opto-mechanical
coupled devices.
| Identifer | oai:union.ndltd.org:canterbury.ac.nz/oai:ir.canterbury.ac.nz:10092/3618 |
| Date | January 2008 |
| Creators | Miller, Paul |
| Publisher | University of Canterbury. Physics and Astronomy |
| Source Sets | University of Canterbury |
| Language | English |
| Detected Language | English |
| Type | Electronic thesis or dissertation, Text |
| Rights | Copyright Paul Miller, http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml |
| Relation | NZCU |
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