Research Projects

Spin coating is a widely utilized method used for making ultra thin films of not only polymers but also any solution process able materials such as sol-gel mediated inorganic materials, liquid crystals, colloids and so on. While spin coated films find application in various types of functional coatings exhibiting optical, bio-medical, anti-microbial and self-cleaning properties, the deposition of the photoresist layer in photolithography is undoubtedly the most significant industrial application of spin coating.It is well known to experimentalists that a continuous film is sometimes not obtained in spin coating, particularly when the concentration of the casting solution (Cn) is extremely low. Traditionally, failure to obtain a continuous film is attributed to pre-existing surface defects like scratches or dust particles, which leads to haphazard and patchy deposits. However, it has been recently realized that under certain conditions, particularly when Cn is extremely low, a collection of nearly equal sized droplets spanning over the entire substrate results during spin coating Formation of such isotropic features in a repeatable manner cannot be defect mediated and is attributed to dewetting of the solution layer during spin coating itself. This phenomenon has been termed as Spin Dewetting and prevents creating very thin films by spin coating. In this proposal, we propose to explore possibilities to suppress spin dewetting, by adding nano particles in trace quantities to the casting solution. Preliminary experiments performed in our group show that addition of nano particles indeed is successful in partially or completely suppressing spin dewetting. As there is absolutely no literature on this topic, it is worth systematically investigate the research problem, which may provide clue for casting even thinner films (than what is achievable in the present day) by spin coating, by suitably suppressing spin dewetting. As spin coating is widely utilized in many areas, including several industrial contexts, therefore the problem proposed here is an unresolved unexplored fundamental problem with extreme practical consequence.