Progress in the physics of block copolymer lithography

The versatility and self-assembling properties of block copolymers have potential applications in nanometer-scale lithography. The feature size and spacing of the structures produced with block copolymer lithography are a few tens of nanometers---a length scale largely inaccessible to currently available lithographic methods. In addition to the immediate possible applications, block copolymers thin films are also a model system for study ordering in two-dimensional systems.; In the first part of this thesis, we use several block copolymer lithographic techniques to fabricate electronic structures. We utilize standard techniques in polymer chemistry and microelectronics lithography; the geometry and characteristic size of the features determine the methods used. Specifically, we fabricate arrays of metallic dots, anti-dots, and wires, which potentially have novel electronic properties.; In the second part, we present a study of shear-induced alignment of thin films of a sphere morphology diblock copolymer which forms hexagonal packed planes. Two-dimensional systems cannot have long range translational order; however, long range order can be produced using an alignment field. In the present case, the dynamic field is the shear stress. We use a stress-controlled rheometer to apply the shear stress through a viscous fluid several orders of magnitude thicker than the polymer thin film. To study the alignment under certain shearing conditions as a function of shear stress, we image ex situ the top layer of the spheres using atomic force microscopy. Below the order-disorder temperature and above the glass-transition temperature, a threshold stress for the alignment exists. Above this threshold, the close-packed direction aligns in the shear direction. Below, the alignment decays continuously to a polygranular morphology (unaligned) at zero stress. We observe alignment only in film thicknesses greater than a monolayer of spheres, which suggests an alignment mechanism similar to that found in uncharged colloids and granular materials. The alignment of our block copolymer thin films using shear stress is a process related to dynamical phase transitions.