Crystal analysis of grain boundaries in boron-doped diamond superconducting quantum interference devices operating above liquid helium temperature

Diamond—the ultimate material for exploring physics of spin-defects for quantum technologies and diamondtronics

“…Kageura et al have used regrowth-induced step edge structure [164] in-situ on single crystalline BDD films, while Mandal et al have fabricated on nano-crystalline BDD films with a fabricated weak-link [162]. Recently, Morishita et al reported SQUID which can be operated above liquid helium temperature (4.2 K) with high reproducibility [165].…”

“…The BDD SQUIDs which have been discussed so far are operational below liquid helium temperature. Recently, Morishita et al have reported BDD SQUID which can be operated above liquid helium temperature (4.2 K) with high reproducibility [165]. These SQUIDs are made based on the step-and trench-type structures.…”

“…It is reported that shear strain, rotation of low-angle grain boundaries and compressive strain in both the structures are one of the reasons for local weakened superconductivity and SQUID performance. For details refer to the following [165].…”

“…All these works [162,164,165] have suggested that BDD SQUIDs can be a good candidate compared to other available SQUID devices. Other Josephson junction constituent materials are typically sensitive to oxidation.…”

“…This may affect the performance of the device. More sophistication is needed to use diamond-based Josephson junctions or SQUIDs, such as in qubits, as it will require miniaturization of the diamond structures [165]. Though theoretical calculation suggests that highly boron-doped diamond can show superconductivity transition temperature as high as 55 K much higher than most conventional superconductors, experimentally it is not achievable till yet.…”