Ordering self-assembled nanostructures

Many innovative applications of nanosciences, such as semiconductor lasers, quantum computing, information storage, quantum cryptography, and semiconductor transistors largely rely on the ability to fabricate long-range ordered nanostructures. However, conventional top-down techniques have mostly reached a bottleneck that thwarts the progress toward future miniaturization needed for the next generation of nanodevices. This constraint imposes the need to develop new manufacturing methods to engineering nanodevices on the single-digit-nanometer scale. Self-assembly, the spontaneous formation of regular arrays, is emerging as one of the most promising avenues for both miniaturization and fabrication.While self-assembly can bring us the direct large scale fabrication of nanostructures, the stochastic nature stemming from symmetry breaking bifurcation inhibits the full realization of ordered nano-arrays. Since the quality of electronic, optical, magnetic and photonic properties of nanodevices depends substantially on the uniformity of their arrangement, avoiding imperfections in self-assembly is important thus forms the central subject of this dissertation.We propose a method for ordering self-assembled nanostructures by imposing control on the deposition using an opaque mask placed a finite distance above the substrate. This choice is motivated by studies of symmetry breaking, which suggest that boundary conditions provide a means to select among all possible broken symmetry states. We have conducted both linear and nonlinear stability analyses to derive optimal control parameters that support specific pattern formation. Numerical integrations of two morphological self-assembly models (2D biphasic surface islands in a monolayer and 3D epitaxial quantum dot growth in Stranski-Krastanow mode) show that the proposed method can indeed give large scale, well organized nanostructures.