Superconducting YBa/sub 2/Cu/sub 3/O/sub 7/ on MgO buffered [100] Si for high frequency applications-buffer layer deposition techniques and processing considerations

The use of MgO as a buffer layer between YBa/sub 2/Cu/sub 3/O/sub 7/ and Si has advantages for microwave applications. MgO has a low dielectric constant, small loss tangent and is relatively stable. Silicon as a substrate material is relatively inexpensive and, more importantly, active semiconductive devices can be imbedded in it. This presents certain challenges from a processing point of view in terms of materials compatibility and growth. We have discovered that maintaining a silicon surface free of any native oxide is critical to obtaining acceptable results. As of this writing we are producing 1.5 cm/spl times/1.5 cm films using both PLD and feedback controlled reactive RF sputtering for the MgO followed by PLD deposited YBa/sub 2/Cu/sub 3/O/sub 7/. The resulting films are c-axis oriented and randomly oriented in-plane according to X-ray diffraction data. T/sub C(R=0)/´s of the films are 70-80 K with transition onsets ranging from 82 to 92 K depending on the method of substrate preparation and the deposition parameters. The most recent processing details, full X-ray characterization of the film structures, and some microwave characteristics will be presented and discussed.