Superconducting flux flow transistors with submicrometer structures

A miniaturization of high critical temperature (T/sub c/) superconducting flux flow transistor (SFFT) was studied. The weak link width in the direction of the vortex flow was varied from 5 /spl mu/m to 10 /spl mu/m. The weak link length in the direction of bias current flow was fixed to 5 /spl mu/m. An increase in the gain was observed as the weak link width decreased. A control line was placed close to the weak link at a distance of 0.5 /spl mu/m to compensate for a decrease of magnetic sensitivity due to the miniaturization. We also improved the characteristics of the SFFT by forming a corrugated structure, which is named corrugation flux flow transistor (CFFT). A submicron patterning of YBa/sub 2/Cu/sub 3/O/sub y/ (YBCO) thin film was performed using focused ion beam lithography. Furthermore, we demonstrated a micro flux flow transistor (MFFT) consisting of a single bridge. The MFFT also operated as well as the CFFT.<
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