Characteristic variation of superconducting thin films modified by an atomic force microscope

Superconducting thin film surfaces were modified in order to test a possibility as a channel of superconducting flux flow transistor (SFFT) by AFM lithography. A conventional lithography method has been employed for superconducting strips which were patterned on LaAlO3 substrates. A region of the strips was selectively oxidized by an AFM probe in the presence of the electric field between the probe and the strip. Then the modified surface was analyzed by AFM, EPMA, and I-V curves. The thickness of the strips increases with the bias voltage as well as the scanning number due to the oxidation. The nonsuperconducting material produced by an AFM lithography process affects the characteristics of SFFT in the flux creep mode of I-V curves. This study represents a dynamic idea to fabricate the superconducting flux flow transistors with nano-channel by the AFM lithography. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)