Fabrication of Superconducting Devices on Diamond

Recent advancements in Chemical Vapour Deposition (CVD) based synthetic diamond growth have opened new avenues for the development of electronic devices capitalising on diamond's exceptional properties, including its high critical field (<i>H_C</i>) and transition temperature (<i>T_C</i>). Achieving superconductivity in lab-grown diamond with high boron concentrations is well-documented in bulk diamond, but limited research focuses on superconducting devices in diamond. The focus of this study was on developing innovative methodologies to engineer micro and nano-scale superconducting diamond devices using thin films of boron-doped nanocrystalline diamond (BNCD) and single crystalline diamond (BSCD). We employ electron beam lithography (EBL) and reactive ion etching (RIE) to engineer highly overdamped and non-hysteretic sub-micron bridges with varying dimensions on superconducting diamond films and low temperature magnetotransport measurements were conducted. A novel fabrication methodology involving neon-ion milling was developed to further define Dayem bridge junctions that demonstrated Josephson effects. The first NCD diamond nano-SQUID was created using these nanobridges as weak links, with a 50 nm loop size.<br/><br/>The nano-SQUID showed a very low flux noise Φ_<i>noise</i> = 0.14 µΦ₀/√Hz at 1 kHz, and concurrent spin sensitivity of 11 spins/√Hz, comparable to that of the lowest noise nano-SQUIDs reported so far in established materials such as niobium. The successful fabrication methodologies on BNCD films were further translated to locally grown BSCD films and superconducting bridges were demonstrated for the first time. In this presentation, we will discuss our results on BNCD nano-SQUIDs and outline our current efforts in developing devices on BSCD films and their corresponding transport measurement results.