Spatial distribution analysis of critical temperature in epitaxial Y-Ba-Cu-O film using variable temperature scanning laser microscopy

• Published in: IEEE transactions on applied superconductivity Vol. 13; no. 2; pp. 2894 - 2896
• Main Authors: Kwon, C., Wang, L.B., Seo, S., Park, B.H., Jia, Q.X.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01-06-2003; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Contact resistance; Electronics; Exact sciences and technology; High-tc films; Laser transitions; Lasers; Microelectronic fabrication (materials and surfaces technology); Microscopy; Physics; Resistance heating; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Superconducting epitaxial layers; Superconducting films; Superconducting films and low-dimensional structures; Superconducting transition temperature; Superconductivity; Temperature distribution; Thermal resistance; Yttrium barium copper oxide; films; scanning laser microscope; Contact resistance; Surface temperature; Epitaxial film; nonuniformity; Non uniform distribution; Spatial distribution; Laser beam; Voltage; Critical temperature; Resistive transition; Temperature fluctuation; High temperature superconductor; Superconducting transition
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2003.812038

We have investigated the spatial distribution of superconducting transition in an epitaxial YBa/sub 2/Cu/sub 3/O/sub 7/ film using variable temperature scanning laser microscope (VTSLM). VTSLM creates an image of the ac voltage response, /spl delta/V(x,y), due to an ac modulated laser beam, which is proportional to dRdT(x,y). In the resistive transition region, there is a strong correlation between the VTSLM images and the resistance of the sample. When the sample is making a poor thermal contact to the heat bath, the large /spl delta/V(x,y) region shifts toward the ends of the bridge while the sample resistance decreases. This result is due to the variation of surface temperature along the sample created by the heating at the contact resistance and/or the poor thermal contact between the sample and the heat bath. However, even after improving thermal contact, we still observe the distribution of superconducting transition. Since the local superconducting transition occurs within 1 K, we conclude that any samples with superconducting transition width larger than 1 K have local nonuniformity.