Design and Fabrication of Nanoscale Bismuth Hall Probes

Scanning Hall probe microscopy is a quantitative magnetic imaging technique with high magnetic flux sensitivity and high spatial resolution. Hall sensors have untapped potential to match the sensitivity of superconducting quantum interference devices (SQUIDs), which are well-known in magnetic microscopy for their flux sensitivity. Furthermore, Hall probes can do so with better spatial resolution. My thesis supports this conclusion with a theoretical calculation while comparing the Hall probe technique to other kinds of magnetic imaging. I have explored further improvements in the overall design and materials of Hall probes. I have obtained and analyzed magnetotransport data for various concentrations of lead in bismuth films and Hall probes. Bismuth, a compensated metal, is a good alternative to semiconductor Hall probes. The presence of electron and hole carriers, though, reduces the Hall effect, and bismuth would be even better for Hall sensors if one kind of carrier were compensated. A doping between 0 and 0.1% lead in bismuth appears to be best for lead-doped bismuth Hall probe operation. I have also made significant progress in the design and fabrication of a more durable Hall probe shape, inspired by hard drive read heads. The novel design should enable operation closer to the sample surface, improving spatial resolution and making it easier to detect flux.