Synthesis and Characterizations of Cobalt Films Electrochemically Deposited from Aqueous and Non-Aqueous Media

Optically absorbent materials have applications in both high-resolution optical imaging and photonic conversion systems. In optical imaging, these materials can be used to reduce the amount of parasitic light. Reducing the parasitic light present in a system increases the possible resolution, making highly optically absorbent materials important for advancements in imaging devices, such as telescopes and optical microscopes. Cobalt films convert absorbed light to heat and transfer it effectively because of their thermal conductivity. This property combined with the characteristics of novel non-aqueously deposited cobalt films (NADCFs) has applications in thermal photonic conversion systems. The characteristics of novel NADCFs are much different than traditional aqueously deposited films (ADCFs) and have much better optical absorbance that can be attributed to their microstructures porosity.

The two films were characterized using UV-Vis Spectroscopy to determine percent absorbance, energy dispersive x-ray spectroscopy (EDS) to infer density, and scanning electron microscopy (SEM) to determine microstructure and thickness. SEM micrographs of the cobalt micro-particles differed depending on solvent (Figure 1). The SEM images and EDS spectra together show a less dense accumulation of micro-particles in the NADCFs compared to the ADCFs. Greater porosity in the 180µm thick NADCF compared to the 115µm thick ADCF was confirmed by the transmission of the x-ray beam in EDS to the copper substrate, showing copper peaks. Thicknesses were determined using cross-section analysis in SEM. The optical absorbance of both films as produced were measured. NADCFs had  >99% absorbance and the ADCFs had 95% absorbance at 490nm.

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