Thermomechanical Nanomolding of Electronic Materials
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The need for extremely small yet highly efficient semiconductor devices has dramatically increased in recent years, driven in part by widespread use of computationally intensive processes such as artificial intelligence. At present, many components in electronics, including transistors and interconnects, have reached nanoscale dimensions. For continued improvement of device design and performance, it is necessary to fabricate and exploit nanomaterials with useful electronic properties. Synthesis of high-quality nanomaterials is often complex and time consuming, however, posing a significant obstacle in screening materials for next-generation electronic devices. This dissertation explores the recently developed nanofabrication technique of thermomechanical nanomolding to produce and characterize nanomaterials with promising electronic properties. Nanomolding involves pressing bulk crystals of materials into nanoporous molds at elevated temperature to obtain nanostructured materials. Unlike other conventional synthesis methods, nanomolding requires simple parameter optimization and has been applied to many different classes of materials, making it a potentially high-throughput technique. The use of nanomolding as a general strategy to fabricate nanowires of layered van der Waals materials is demonstrated for the first time. A detailed mechanistic study is presented, showing that the van der Waals layers orient parallel to the nanowire growth axis in order to minimize surface energy. Nanomolding of a covalently bonded and metastable material, Mo4P3, is also demonstrated for the first time, further expanding the materials scope and capabilities of the technique. Finally, we use nanomolding to screen a potential candidate for replacing copper in interconnects, CuAl2. CuAl2-x nanowires are fabricated to exhibit much higher resistivities than copper and bulk CuAl2, likely due to the off-stoichiometry which increases electron scattering. Finally, nanomolding of CoSn, a topological Kagome metal with highly anisotropic Fermi velocity, is proposed as a future project.