Chromogenic properties of nanostructured periodic and non-periodic transition metal oxide thin films for optical and photonic applications

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The objective of the proposed research is to bring together the fields and virtues of 1) Chromogenic properties of transition metal oxide (TMO) thin films and 2) periodic and non-periodic nanostructuring of these thin films to enhance their properties. TMO thin films exhibit various kinds of chromogenic properties due to their multiple oxidation states and their special structure. Their ability to reversibly change their optical properties under the influence of external electric field (electrochromics), heat (thermochromics) and light (photochromics) is termed chromogenics. This chromogenic performance is found to depend very strongly on the film nanostructure which induces favourable traits required for efficient coloration and bleaching. Hence, the main goal of the work proposed is to establish the correlation between the film nanostructure and the chromogenic performance. The experimental work will focus on the thin film preparation methodology to induce the precise nanostructure and to characterize the chromogenic properties under various external influences. In-depth theoretical modelling work will be undertaken to comprehend the underlying physics of the chromogenci phenomena especially as it relates to nanostructured materials. Both periodically and non-periodically nanostructured TMO thin films will be studied. The knowledge gained from this research will be applied towards enhancing the optical and photonic perforamnce of the films. The non-periodic structures are very interesting from the point of view of their enhanced optical performance while the periodic structures are important for their unique ability to selectively manipulate light propagation (through photonic bandgap). The reversible and continuous tuning of the photonic band gap is at the heart of the work to be undertaken. Hence, the ultimate goal in both the cases is to achieve an interactive external control of optical and photonic properties of importance in various applications such as smart windows, sensors and optical circuitry. Evaluation of the application potential of the optical and photonic devices based on these nanostructured TMO thin films will be an important aspect to be addressed in the work.