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 degrees C, and exposed to low-level ultraviolet light. (C) 2010 American Institute of Chemical Engineers AIChE J, 56: 3206-3211, 2010