Ion Beam Thinning and Polishing of YBa sub 2 Cu sub 3 O sub 7 Films.

Successive ion beam milling at grazing angles of a 2400 angstrom - thick c-axis oriented YBa sub 2 Cu sub 3O sub 7 film is shown to give smooth films which superconduct at thicknesses on the order of tens of angstroms. The thinning and polishing process is characterized at successive milling stages using resistance transitions, X-ray analysis, scanning electron microscopy, and Rutherford backscattering and channeling analysis of composition and surface quality. As thinning proceeds, SEM and diffraction features associated with a-axis texture are removed and crystalline quality, as measured by X-rays and channeling, markedly improves. PACS numbers: 74.75+t, 74.70. Vy, 81.40.RS.