HTS Flux-Flow Channels On Silicon Wafers

New process/structure designs for the channel in the vortex flux-flow transistor (VFFT) have been explored utilizing thin YBCO films on silicon wafers. Two designs are reported: first, films on micromachined Sl(100) surfaces, and second, films ex-situ annealed in bromine. Shallow trenches are anisotropically etched into Si(100) wafers forming (111) facets, and films are grown by pulsed laser deposition. Bromination processing of YBCO is preceded by mild deoxidation and followed by a re-oxidation. Broad-area characterizations by R(T), dc magnetometry, and ac susceptibility are given. On Si(100), epitaxial YBCO films have sharp R(T) transitions and high Jc. Films on Si(111) and brominated films have a toe in R(T) at Tco, and lower Jcmore easily reduced by H. YBCO falling across the trenched surfaces or small brominated regions have R(T), I-V, and Ic promising for use as flux-flow channels in VFFT.