Physical vapour deposition at oblique angles produces coatings that have oriented internal structure, a consequence of self-shadowing and limited diffusion. Structured media have a number of useful properties, including form birefringence which affects the polarization of light. Whilst oblique deposition technology is mature, there is room for further exploration to open up new applications and provide further insight. One door only recently opened is lithographic patterning, and this thesis seeks to map out part of that frontier. Lithography allows rapid replication of a pattern, and is being extended to the nano-scale, via two routes identified as "top-down" and "bottom-up". In this thesis bottom-up processing is pursued as a secondary theme, developing computer programs for investigation of the effect of substrate patterning on growth and subsequent birefringence. The primary focus is the application of top-down patterning to obliquely-deposited polarizing elements, for the production of pixellated polarizing arrays.
The growth of obliquely deposited coatings is well understood, and the process has been developed using dynamic substrate rotation to produce several interesting morphologies. Standard results of computer simulations are replicated for illustration. The relationship between morphology and optical properties has been extensively studied from an empirical standpoint, resulting in production of polarizing elements such as retarders, linear- and circular- polarizers. Surprisingly little study has focussed on simulation of the optical anisotropy of arbitrary structures, and here programs are developed for initial prediction of the birefringence of coatings deposited over patterned substrates.
Top-down patterning approaches are directly applied to obliquely-deposited dielectric coatings. Standard reactive ion etching protocols are tested, particularly for silicon films, measuring the effect of deposition parameters on etch-rate. Lift-off patterning at significantly oblique angles requires special attention, and an undercut tri-layer process is developed, resulting in patterning of chiral oxide films. Additionally a novel masking process is developed, that allows the production of pixellated arrays comprised of different polarizers in a single coating operation. One such array is used as the essential component in the production of a space-multiplexed array polarimeter.
| Identifer | oai:union.ndltd.org:ADTP/217374 |
| Date | January 2005 |
| Creators | Arnold, Matthew David, n/a |
| Publisher | University of Otago. Department of Physics |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://policy01.otago.ac.nz/policies/FMPro?-db=policies.fm&-format=viewpolicy.html&-lay=viewpolicy&-sortfield=Title&Type=Academic&-recid=33025&-find), Copyright Matthew David Arnold |
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