Fabrication and Evaluation of YBa2Cu3O7-δ Probe for Scanning Probe Microscopy

We proposed, fabricated, and evaluated a high-temperature superconducting probe made of YBa
₂
Cu
₃
O
_7-δ
(YBCO) for scanning probe microscopy. A c-axis-oriented bulk was cut into a rectangular solid rod (0.5 × 0.5 × 10 mm
³
) using a fine cutter machine. The transition temperature of the rod was approximately 90 K, which was almost the same as that of the original bulk, indicating no critical damage to the superconductivity owing to the cutting process. One end of the rod was polished to a pyramid shape with <100-μm radius of curvature, and the apex was further sharpened to ∼1 μm using a focused Ga ion beam. The penetration depth of Ga ions from the YBCO surface was much less than 1 μm at an acceleration voltage of 40 kV, suggesting that the chemical composition was conserved inside the rod. An YBCO probe was installed in an atomic force microscope (AFM), where the probe temperature was set at 300 K at the time. Depending on the tip radius, a clear AFM image was obtained by gluing the probe to a quartz-tuning fork.