Pulsed laser deposition of patterned multilayers for HTS device fabrication

Pulsed laser deposition (PLD) has been used to deposit high quality multilayer thin films of Permalloy/Au/YBCO onto (100) oriented substrates of MgO and SrTiO/sub 3/. These multilayer structures are currently being used to investigate the effect of the injection of polarized electrons on the order parameter of high temperature superconducting (HTS) thin films. To observe this effect, thin films with sharp interfaces (to minimize spin scattering) and low contact resistance will be required. The morphology and structure of the deposited films has been investigated using scanning electron microscopy and X-ray diffraction, respectively. The electrical properties (T/sub c/ and J/sub c/ (77 K, B=0)) were measured for both unpatterned and patterned films. Films were patterned using both wet chemical and ion beam (Ar/sup +/, 1 KeV) techniques. Unpatterned films were characterized inductively as having T/sub c/'s>88 K and J/sub c/'s>1 MA/cm/sup 2/. Wet chemical etching resulted in films with slightly reduced T/sub c/'s and J/sub c/'s/spl sim/10/sup 3/-10/sup 4/ A/cm/sup 2/ however, no reduction in T/sub c/ or J/sub c/ was observed for dry etching. A lift off procedure using PMMA/Cu has been explored to define smaller (/spl sim/400 /spl mu/m) features. Extremely low contact resistance's (<10/sup 7/ /spl Omega/ cm/sup 2/) have been measured for Au films deposited by PLD onto YBCO. The low contact resistance is attributed to the high kinetic of the Au particles. These device structures can be used to develop simple HTS based transistors.