Periodic and non-periodic nanostructured chromogenic thin films and devices

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The principal objective of the current research proposal is to undertake an in-depth study of the chromogenic properties of transition metal oxides (TMO) in their nanostructured form and to use this knowledge to design thin film smart systems with enhanced performance. Chromogenics is the field of study of materials in which a reversible optical property change can be induced by applying various external forces such as an electric field (Electrochromics), heat (Themrochromics), light (Photochromics) and more. Amongst the inorganic materials, the TMOs such as, Tungsten trioxide (WO3), Vanadium dioxide (VO2), Molybdenum trioxide (MoO3) and others, are known to exhibit a very efficient form of chromogenic (switching) properties and have become the object of intense basic and applied research in recent years. The interactive nature of devices based on these materials are making way to their application as smart systems in various fields. Research carried out in my laboratory (Thin Films and Photonics Research Group) at Université de Moncton over the last few years has amply demonstrated the significance of working with the nanostructured form of the various TMOs. The nanostrucuring of the above said TMO thin films has been achieved by using certain innovative and advanced methods. It is found that this approach to TMO fabrication not only leads to better performing TMO based thin film devices but also to the possibility of inducing new properties into them. Hence, an important part of the proposed work on the basic research side will be dedicated to the in-depth understanding of the correlation between the induced nanostructure and the chromogenic properties of the TMO thin films. The aim is to understand the fundamental physics and chemistry related to the properties of the nanostructured TMO thin films and their switching properties. The reduction of the dimensions of these materials to nanometric level is expected to bring about numerous changes due to the a) enormous grain boundaries affecting the electron transport, b) change in the optical constants (n,k) and porosity affecting the light propagation in these materials, c) chemical behaviour due to the enormous internal surface created around the grains and more. Also, these changes are complex and even more interesting from their fundamental study point of view due to the reversible dynamic (switching) behaviour of the nanostructured TMO thin films. The periodic nanostructuring of these TMOs are expected to lead to very interesting and tunable photonic properties. Further in-depth work based on my 2010 patent on chromogenically tunable photonic properties will be undertaken. On the applied research side, the aim is to use this in-depth knowledge gained on these periodically and non-periodically nanostructured TMO thin films to fabricate better performing thin film switchable smart systems for application in various sectors such as energy management, display devices and more.