YBa/sub 2/Cu/sub 3/O/sub 7-x/ 45° [001] tilt grain boundaries induced by controlled low-energy sputtering of MgO substrates: transport properties and atomic-scale structure

Grain boundaries can act as weak links in the high Tc materials. If properly controlled, these grain boundaries can be used in various device applications. We have been able to reproducibly form 45° [001] tilt grain boundary junctions in YBa2Cu3O7-x thin films. The films were grown-on MgO substrates using a pre-growth substrate treatment. A low energy broad beam argon ion source was used to irradiate a select region of (100) MgO substrates. The film on the milled portion of the substrate grows predominantly with a grain orientation rotated 45 degrees about the c-axis with respect to the grain on the unmilled portion. Backscattered electron Kikuchi patterns have been used to confirm that the rotation occurs across the entire milled portion of the substrate. Transport properties of these films are discussed and related to high resolution electron microstructural and microchemical analyses of the grain boundaries. This technique has potential use in device applications as a method for controlled grain boundary engineering.