Generating MgO single- and bi-crystal templates on hard and soft substrates using ion beam assisted texturing process

Ion beam assisted texturing process (IBAD) has provided a promising approach for development of epitaxial thin film devices on various low-cost nontextured substrates. The interface between the IBAD template and the substrate surface has been found to play the key role in texture quality of the template. In this work, we have investigated texture evolution of IBAD MgO templates on several technological important substrates including cereflex (hard) and polyimide (soft). The former may be an alternative of low AC loss substrates for high-T-c superconductor tapes but has extremely rough surface incompatible to MAD MgO process. By developing a surface smoothening process, high-quality bi-axially textured MgO templates have been achieved on Ceraflex. On the amorphous polyimide films, preferential sputtering of the ion beam prevents texturing of IBAD MgO. With thin buffer layer on top of the polyimide surface, the preferential sputtering of polyimide surface can be minimized and highly textured MgO template with in-plane full-width-at-half-maximum of 9-10 degrees and out-of-plane full-width-at-half-maxiniuni similar to 3.0 degrees have been obtained. This method may provide a practical route for fabricating suspended epitaxial devices on polymer sacrificial layers as demonstrated. In addition, a two-step process was developed to generate textured MgO bicrystal templates on glass and Si substrates. After the first-step IBAD process, a mask was generated on the MgO template and a selected area was removed before a second MgO template was laid at a selected in-plane angle. The flexibility of this technique makes it possible to fabricate various two dimensional novel bicrystal devices of microscopic scales.