Controlling the Composition and Morphology of Si1-xGex Nanowires

Silicon (Si) and germanium (Ge) semiconductor nanowires can be utilized in next generation electronic, photonic, and energy conversion devices. Si, Ge, and Si1-xGex materials are also well studied and currently used in industry. Optoelectronic properties, such as the band gap, can be tuned by modulating the alloy composition, thus allowing for a wider range of uses. The focus of this project was to create arrays of Si1-xGexalloy nanowires with varying, but simultaneously uniform, compositions. This goal has been difficult to achieve to date. Nanowires were grown with the gold catalyzed, bottom-up, vapor-liquid-solid mechanism throughout the compositional range. Using scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), and Raman spectroscopy, we demonstrated control of Si1-xGex alloy composition, but struggled to achieve highly aligned arrays. Nanowires frequently kinked to the <112> directions and underwent conformal deposition, which resulted in tapered structures. Therefore, we employed a sidewall species, methylgermane, in an attempt to overcome this.