Faculty Advisor: Martin GrevenHigh temperature superconductivity is a phenomenon that exhibits considerable promise in the advancement of technology. The alluring premise of zero resistance at manageable temperatures offers unparalleled minimization of power loss, which necessitates extensive research to aid in understanding the operation of HTSCs (High Temperature Superconductors). This study focused on the well-known HTSC HgBa2CuO4+δ (Hg1201). Specifically, the growth procedure was modified using liquid Hg in an attempt to improve crystal quality and size. The frequency of high-quality crystals increased following the change to include liquid mercury in the growth. Additionally, several large crystals were isolated in a higher frequency than with the old growth method. It was also the objective to perform carefully monitored anneals of Hg1201 crystals to modify their oxygen content, with an emphasis on low doping. This was done in order to obtain samples for relevant future experiments. Four anneals were carried out: one highly reduced anneal, two lightly reduced anneals, and one oxidized anneal. These trials yielded inconsistent results.This research was supported by the Undergraduate Research Opportunities Program (UROP)