Fabrication of Super Invar Micro- and Nano- Structures by Electrodeposition for Low Thermal Expansion Applications

5 wt % Co, are of both theoretical research and practical interest due to the anomalous codeposition behavior, the preferential deposition of less noble metal, and to the material's low coefficient of thermal expansion, CTE. A better understanding of anomalous codeposition allows for controlling the deposition rates of individual Fe, Ni, and Co metal during codeposition and hence the composition. In addition, electrodeposited Super Invar alloys are of practical interests due to their potential applications in industry, particularly in micro-electro-mechanical systems (MEMS) due to the material's near zero CTE at room temperature in bulk materials. In practice, however, it is difficult to predict the alloy composition and control the composition gradient along the direction of growth, due to the anomalous codeposition behavior. Super Invar has not been widely studied; most studies of the ternary FeNiCo have been focused on Co-rich alloys due to their magnetic property over the last twenty years. In addition, there is an absence of understanding the CTE in electrodeposited Super Invar structures and how it is influenced by the electrodeposition parameters. The objective of this research is to study the electrodeposition of Super Invar alloy thin films and micro-posts, and nanowires. First, thin film deposition of FeNiCo alloys is investigated in order to determine the most appropriate applied current density into desired recessed features. Based on the conditions of thin films, different pulse plating parameters are applied and the deposit composition distribution along the length of the microstructures was examined. Pulse plating is critical in achieving a uniform composition distribution in 100 µm deep features. Using a pulse scheme with a low, non-zero current step introduces more cracks into the deposit, characterized by SEM. The coefficient of thermal expansion (CTE) of the micro-post arrays is also determined and exhibits negative values in the axial direction, i.e., the micro-posts shrink with