研究目的
To report on the fabrication of micron-sized constrictions in YBCO thin films using the femtosecond laser technique and to determine the critical current IC of the constrictions at 77 K.
研究成果
A femtosecond laser-based technique for the fabrication of micron-sized constrictions on YBCO thin films was developed. Three micron-sized superconductive constrictions of width 2.88, 1.72, and 1.69 μm were fabricated. The size of the superconductive phase of the material that remains unchanged determines the magnitude of the critical current produced by the sample. Due to inhomogeneities created by the laser, Abrikosov vortices do not form, the AC Josephson-like effect is not observed, and current flows by one-dimensional depairing technique.
研究不足
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 rather than by the coherent motion of Abrikosov vortices.
1：Experimental Design and Method Selection:
The femtosecond laser technique was used to fabricate micron-sized constrictions in YBCO thin films. The constrictions were designed in the shape of the letter 'S' to regulate both the length and the width of the constriction.
2：Sample Selection and Data Sources:
Commercially available YBCO thin films from ceraco ceramic coating company GmBH were used.
3：List of Experimental Equipment and Materials:
A femtosecond laser with a wavelength of 795 nm, power ranges from 0 to 1000 mW, and pulse repetition rate or frequency ranges from 1 to 2 kHz was used. The YBCO thin films had dimensions of 9 × 9 mm, single sided 200 nm with a grain orientation of (001), on 10 × 10 ×
4：5 mm substrate. Experimental Procedures and Operational Workflow:
The laser was set to an optimized power of 2 mW and the pulse repetition rate at 1 kHz, and the laser feed rate was set to 333 μms-
5：A program was written in G-code to control the movement of the translation stage while cutting with the laser. Data Analysis Methods:
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.
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