Methods and mechanisms for the fabrication of highly-ordered colloidal crystal arrays

• Main Author: Thomson, Niall Rae
• Other Authors: McComb, David ; Bower, Chris
• Published: Imperial College London 2008
• Subjects: 548
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484799

Colloidal crystals have been the focus of intense scientific interest owing to the wide range of proposed applications, including photonic crystal devices, sensor arrays and templates for three-dimensionally ordered macro-porous materials (3-DOM). The broad spectrum of interest stems from the exciting structural properties these materials possess, i.e. porosity, interconnectivity and periodicity. The fabrication of colloidal crystals stripes with features at the pitch of 25 - 450 μm is of interest for a number of reasons: First, to permit the integration of colloidal crystal structures into devices; second, to increase understanding of the mechanisms governing colloidal self-assembly; and third, to allow the creation of arrays of heterostructures combining colloidal crystals of two or more sphere sizes. However, it remains a significant challenge to direct the self-assembly of three-dimensionally periodic colloidal crystals reproducibly over large areas, as the patterning techniques are often time consuming and not suitable to scale-up. In this thesis the successful formation of highly-ordered colloidal crystal stripes over large areas is presented using the combination of two easily integrated techniques, micro-contact printing (μ-CP) and evaporative vertical deposition (EVD). The large area over which directed deposition has been achieved and the combination of μ-CP and EVD are novel. The technique has also been demonstrated on functional substrates. This versatility and scalability represents a significant step towards the formation of low-cost devices based on these materials. Characterisation by reflectance spectroscopy, white light interferometry, and optical and scanning electron microscopy establishes the high spatial selectivity of the technique and the three-dimensional periodicity of the striped colloidal crystal arrays formed.