Nano/femto-second laser based nano structuring of ultra thin films

Nanofabrication, at lateral resolutions beyond the capability of conventional optical lithography techniques, is demonstrated here. Various nanofeatures (nanogrids, nanocraters, nanocurves) were machined, with high spatial resolution (similar to10-12nm), on thin metallic and semiconductor films by utilizing the enhanced field that exists underneath a scanning microscope tip irradiated with a laser beam. For the first time in the published literature, recrystallization results of thin a-Si films, at the nano-scale, are being presented to demonstrate the utility of this machining scheme as an effective 'nano'- laser source. Attempting to understand the modification mechanism and the physics involved, numerical simulation studies were performed to evaluate the field enhancement underneath the tip and the 'femtosecond laser - thin film' interaction dynamics in general. For the former study Finite Difference Time Domain simulation was carried out to evaluate the spatial distribution of the field intensity in the near field of the SPM probe tip. The later study employed finite-difference numerical method to solve the hyperbolic two-temperature scheme used to model the interaction. Possible applications of thin film structuring and its use as a mask may be in the areas of high-resolution nanolithography, nanofluidics, controlled nanodeposition, ultra high-density data storage, nanoelectronics, nanophotonics and various nanobiotechnology related applications.