Three-dimensional control of layer by layer thin films via laser modification

Abstract

A novel modification to the traditional layer by layer process that adds three-dimensional control to the technique is introduced. In this modification to the process, the substrate is irradiated with laser light during the polycation and/or polyanion dipping cycles. An array of PAH/PCBS polymer thin films were fabricated using the laser modified approach with varied bilayer numbers, laser powers, and laser irradiation times. The modification was conducted with a semiconductor laser with powers from 1.1 to 5.5 W at 450 nm. Surface profilometry results show a change in height of more than 500 nm for a 55 bilayer PAH/PCBS thin film. For 25 bilayer films, the addition of laser modification during the PAH cycle leads to a reduction in absorbance of up to 54% compared to the areas not being irradiated. The absorbance at 365 nm associated with PCBS shows a nonlinear relationship with bilayer number, in contrast to the usual linear relationship between absorbance and bilayer without laser irradiation. By adjusting irradiation time, irradiation power, number of bilayers, and the location of irradiation, a variety of structures with controlled thicknesses can be fabricated.