Controlled self-assembly in homopolymer and diblock copolymer

This thesis work studies the process, mechanism and control of self-assembly in homopolymers and diblock copolymers. These studies are aimed at finding novel patterning methods that can lead to low cost lithography technologies capable of creating micrometer to nanometer patterns over a large area.; We first present a new phenomenon called Lithographically-Induced Self-Assembly (LISA) that can create ordered arrays of pillars in a homopolymer film with a mask placed close to its surface. We demonstrate that the shape, size and morphology of the ordered pillar arrays can be controlled with a patterned mask. A model is developed based on the instability in a fluidic film induced by the Coulomb force from charge accumulation in the polymer film and the mask. Experimental results are shown to support the model. We also investigate the behavior of defects that destroy the ordering of the LISA array and propose ways to prevent them. This self-assembly phenomenon is used as a patterning technique to define the active area of an organic light emitting diode (OLED). The device shows significantly improved lifetime due to the restriction of defect growth.; Another patterning technology that is closely related to LISA, Lithographically-Induced Self-Construction (LISC), is also introduced. LISC can form mesas of polymer from the initial thin film and they inherit the shape and size of the mask patterns. A model based on the dynamics of LISA pillar formation and mass conservation is presented and provides a guideline for choosing LISC process parameters.; In the final part of the thesis, we study a technique to control the orientation of diblock copolymer phase separation in a thin film by applying a pressure on the film through a flat mask. The result is a well-ordered grating pattern of the phase separation with a period of tens of nanometers. The effect of pressure and film thickness on the final pattern is investigated by experiments. We suggest that the increased ordering is due to the shear stress in the thin film induced by the uneven pressure on the mask.