Development of superconducting single-photon detectors based on NbTiN and graphene

Superconducting Nanowire Single-Photon Detectors (SNSPDs) offer several advantages over traditional photodetectors. However, they have limitations related to their latching dead time and dark count rate. This research explores the integration of graphene as an on-chip thermal and electrical shunt in NbTiN superconducting detectors, marking the first application of a 2D material in this capacity. We investigate the impact of graphene on the performance of NbTiN detectors within the multiphoton regime. The NbTiN nanowires are produced via DC reactive magnetron sputtering with a thickness of 25 nm and optical or electron beam lithography onto SiOx/Si substrate. The monolayer graphene is grown by Chemical Vapor Deposition (CVD) and transferred on top of the nanowires. The characterization of the samples has been performed in a close-circuit cryostat setup (3.8 K). The experimental of nominally identical devices with and without graphene, reveal a shift in critical temperature (Tc), a broader superconducting transition, and a significantly reduced electrical hysteresis in the hybrid system. Preliminary results show a non-latching behavior of NbTiN meanders with graphene under pulsed laser illumination of 640 nm photons with a repetition rate up to 1 MHz, emphasizing its efficacy as a shunt resistor speeding up the detector and increasing the detection efficiency. The increased FWHM also highlights the role of graphene in the electrothermal feedback and dissipation. In conclusion, this pioneering work contributes valuable insights into the intricate interplay between 2D materials and superconducting detectors, paving the way for future advancements in this field.