Date of Award
Master of Science
A methodology was developed for isolation and transfer of 1-4 monolayer graphene from both Cu and Ni foil and Ni/SiO2/Si layered substrate types for use as electron transparent windows in environmental electron microscopy and spectroscopy. The graphene membranes were transferred onto disc "frames" made of stainless steel containing 3-10 μm diameter apertures. Such frames "windowed" with the graphene membrane are assembled into the custom designed environmental cell (e-cell) which contain a specimen immersed in the desired liquid or gaseous environment, and are compatible for imaging with a conventional scanning electron microscope (SEM) (in this case, a Hitachi 4500 SEM). Gold nanoparticles (50 nm) colloidal in water served as model specimens and were observed inside the e-cell using both secondary electron and backscattered electron detectors. An imaging induced radiolysis of water was observed at higher electron doses, which manifested itself in the formation of bubbles growing and coalescing under the enclosed graphene surface. Key SEM imaging parameters responsible for driving the radiolysis phenomena were addressed.
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