We have experimentally studied the influence of the focused ion beam (FIB) microfabrication on the superconducting properties of exfoliated thin films of layered superconductor NbSe2 through transport measurement. We observed significant decrease of the residual-resistance ratio (RRR), indicating the formation of defects by the FIB. Although clear superconducting transition was seen before the FIB microfabrication, after FIB it was blurred, and one sample exhibited insulating behavior. The possible origins of the changes in the superconducting properties are discussed.
We have experimentally studied response of a superconductor NbSe2 flake to perpendicular magnetic fields using small tunnel junctions. The NbSe2 film (lateral size ∼ several μm, thickness ∼ 50 nm) was obtained using the mechanical exfoliation of a bulk crystal and was transfered on top of predefined Au electrodes, forming an Au/NbSe2/Au double SIN tunnel junction system. At 4.2 K, between the lower and upper critical fields (H
C1 and H
C2), the voltage of the Au/NbSe2/Au structure under constant current of 1 μA exhibited random-telegraph-noise-like fluctuations as a function of the magnetic field which was applied perpendicular to the NbSe2 flake. The origin of the voltage fluctuations is discussed.
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