Trillions of Quantum Dots, Fingerprints, Nanolithography with Diblock Copolymers, and the Formation of Striped Patterns

In order to develop new technologies for lithography on the nanometer scale we have been investigating the use of diblock copolymers, systems which form periodic structures on the 5-50 nm scale. Diblock copolymers consist of A and B monomers which are immiscible and would normally phase separate like oil and water. When they are covalently bound as A-A .-A-A-B-B-. B-B-B-B the best they can do to avoid each other is to put all the A ends together in spheres or cylinders surrounded by the B's. We have used a monolayer mask of the diblock to transfer the periodic patterns to a number of different substrates as holes, posts, and semiconductor and metal quantum dots producing ultradense arrays, e.g. 3 trillion dots on a 3 inch wafer. Along the way we have developed novel methods for three dimensional imaging on the nanometer scale and for tracking the annealing of the two dimensional monolayer patterns. Time lapse atomic force microscopy of the cylindrical phase (which forms fingerprint like patterns in the monolayer) reveals the solution to a common problem in many fields of science, how striped patterns order. Instead of two defects (disclinations) annihilating our movies show quadra-defect annihilation explaining the much slower (fourth root time) behavior seen in many striped systems.