| Popis: |
There is increasing interest in discovering novel superconducting materials for use in photodetection. Superconductivity has for a long time been known to exist in layered materials but with recent advances in two dimensional (2D) materials processing, it is now possible to cleave these materials down to single and few layer thicknesses. For the first time we are now in a position to fabricate superconducting strips that are only a single molecular layer thick. Such an ultimately thin material offers exciting possibilities in both photodetection and materials science research. Presented here, is an original work investigating the photoresponse of few-layered niobium diselenide (NbSe2), a superconducting transition metal dichalcogenide. Current biased NbSe2 samples were tested optically at 1550 nm at cryogenic temperatures down to 350 mK. They show bolometric behaviour where the output signal amplitude increases with absorbed laser energy. At high currents, samples were observed to latch to intermediate resistances and become less sensitive to further laser excitations. A model has been developed which describes the observations as the result of a thermally stable hotspot due to the balance of Joule heating and in-plane heat conduction. These measurements mark the first successful demonstration of a photo-response in an exfoliated superconducting sample and will hopefully pave the way for future integration of 2D materials in complex optical systems. |
