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Title: Reflection anisotropy spectroscopy and scanning probe microscopy studies with applications to liquid crystal alignment layers
Author: Macdonald, Brian Fraser
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2002
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Homogeneous alignment of liquid crystal (LC) molecules is fundamental to the fabrication and optimum operation of LC devices. As a consequence of employing alignment layers with directional properties, the alignment of LC molecules is promoted. The most commonly used technique to fabricate LC alignment layers is by mechanically rubbing polymer films. However, reductions in production costs and further advancements in LC technology are now being hindered by the rubbing technique and so either a new technique or monitoring of the current technique is required. In these studies, a monitor of the rubbing technique and of the potential replacement techniques is demonstrated. By constructing a surface sensitive technique, traditionally used to monitor semiconductor growth, and applying it to alignment layers, the first uses of reflection anisotropy spectroscopy (RAS) to monitor the fabrication of LC alignment layers are presented. This technique, in conjunction with atomic force microscopy (AFM), has been successfully used to study a number of different variables of the rubbing technique and as an in-situ real time monitor of the photoalignment and atomic beam etching techniques. Of these, the etching technique has shown the most potential to replace mechanical rubbing yet it is probably the least understood. An interesting by-product of these alignment layer studies has been the introduction of an extension to the normal RAS technique. By using examples such as doubly rubbed alignment layers, angular dependent RAS (ADRAS) has been shown to be capable of isolating and monitoring optical anisotropy from multiple sources within a single system. To increase understanding of the etching technique, the complex polymer surfaces were replaced by a model system: a Copper single crystal. The complexity of these studies was then increased by the introduction of vicinal surfaces and the adsorption of chiral molecules onto the Cu(110) surface. Both of these changes alter the characteristic spectra but the latter also has potential to allow further uses of ADRAS as the chiral molecule is known to lie at a specific angle to the rows of Copper atoms.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available