Micron-Sized Constrictions Fabricated Using the Femtosecond Laser Technique on YBCO Thin Films

Abstract

In this paper, I report on the fabrication of micron-sized constrictions in YBCO thin films using the femtosecond laser technique. The constrictions are S-shaped superconducting weak links fabricated on YBCO thin films. The constrictions show a measurable superconducting current flowing through them. Current-voltage (I–V) characteristics were used to determine the critical current IC of the constrictions at 77 K. The width of the constrictions was determined at the narrowest point using SEM (scanning electron microscope). Three micron-sized constrictions were fabricated with a width of 2.88 μm, 1.72 μm, and 1.69 μm and a length of 5 μm. Based on the width and length of these constrictions in relation to the coherence length (ξ) of the YBCO, these constrictions should conduct supercurrent by Abrikosov vortices. The SEM images show that the femtosecond laser heats the samples beyond the geometric boundary, damaging some of the superconductive phases of the YBCO constrictions. As a result, the constrictions conduct current by one-dimensional depairing.