Directed self-assembly by photostimulation of an amorphous semiconductor surface

A method for nanoscale directed self-assembly is demonstrated that employs an amorphous semiconductor containing subcritical nuclei for crystallization. This strategy combines attractive features of top-down and bottom-up approaches by exploiting the self-organization capabilities latent in amorphous materials, but in a way that can be controlled by optical or electron beam exposure tools. The method was demonstrated with amorphous TiO₂ deposited on silicon, heated to 270°C, and exposed to low-level ultraviolet light.