Formation of Single-crystal CoSi 2 Buffer Layers on Si(100) Substrates by High Dose Co Ion Implantation for the Depositi
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Formation of single-crystal CoSi2 buffer layers on Si(100) substrates by high dose Co ion implantation for the deposition of YBa2 Cu3 O7–x thin films Yijie Li,a) P. Seidel, F. Machalett, S. Linzen, and F. Schmidl Institut f¨ur Festk¨orperphysik, Friedrich-Schiller-Universit¨at Jena, Helmholtzweg 5, D-07743 Jena, Germany (Received 18 January 1995; accepted 21 January 1997)
High quality single-crystal CoSi2 layers have been successfully formed on Si(100) using low energy high dose Co ion implantation followed by subsequent annealing method as a buffer layer for the deposition of YBa2 Cu3 O7–x (YBCO) thin films. Rutherford backscattering spectrometry with channeling (RBS-C) measurements showed that CoSi2 layers after annealing at temperatures between 850 and 950 ±C had a minimum yield xmin of about 3%. X-ray diffraction (XRD) spectra revealed that CoSi2 layers had the same orientation as the Si(100) substrates. Phi scan XRD spectra proved that CoSi2 layers epitaxially grew in the cube-on-cube epitaxial growth mode with respect to the Si(100) substrates. YBCO films and CeO2yYSZ buffer layers were deposited on CoSi2ySi(100) substrates via laser ablation and electron beam evaporation, respectively. u-2u, v, and f scan XRD spectra illustrated that YBCO films and CeO2yYSZ buffer layers had the epitaxial structure both in a-b plane and along the c-axis. YBCO films grown on this multilayered structure demonstrated excellent superconducting properties with the zero resistance transition temperature Tc0 of 87–90 K. The transition width (DTc ) was about 1 K. Orientation and epitaxial crystalline quality of YBCO films and CeO2yYSZ buffer layers were confirmed by XRD and RBS-C characterization. All films consisted of c-axis oriented grains. RBS-C spectra indicated a high degree of crystalline perfection with a channeling minimum yield for Ba as low as 8%, and interdiffusion between the YBCO film and buffer layers or between the YBCO film and the substrate was limited. This multilayer system shows the possibility for the application of YBa2 Cu3 O7–x thin films on technical Si substrates in the field of hybrid superconductor-semiconductor technology.
I. INTRODUCTION
Since the discovery of high temperature superconductors, high quality superconducting YBCO thin films with very high critical current density (.106 Aycm2 ) have been successfully grown on insulating single crystalline substrates, such as SrTiO3 , yttria-stabilized ZrO2 (YSZ), LaAlO3 , MgO, etc. These films can be used to make SQUID’s (Superconducting Quantum Interference Device), flux transformers, and other superconducting devices. But for the purpose of application in the field of hybrid microelectronics and in order to reduce the product costs, it is necessary to deposit high quality YBCO films on technical substrates like Si, GaAs, or sapphire. Unfortunately, directly deposited YBCO thin films on Si substrates generally have a very poor superconductivity due to the interdiffusion and the lattice a)
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