Vortex behavior in the finite-sized square network of Pb

Vortex behavior of superconducting finite-sized networks with 2 × 2 and 10 × 10 hole arrays has been investigated in a weak magnetic field. Photoresist films spin-coated on silicon substrates were first processed to draw network patterns by using the electron beam lithography. Then, the Pb networks have been made up by a lift-off technique after depositing Pb film on the resist patterns. The thickness of deposited Pb films is 200-250 nm. Photoresist film was coated to protect Pb networks fabricated on silicon substrates (4 × 4 mm). We carried out magnetization measurements of the Pb networks by a SQUID magnetometer as well as vortex image observations by a SQUID microscope. Matching peaks appeared in magnetization curve when a magnetic field was scanned from −4.7 G to +4.7 G. The magnetic field in SQUID microscope measurements was chosen as the integral multiples of the matching field Hϕ, where the scanning area typically covers 128 × 128 μm with 1- or 2-μm step.