Title :
Relationship between electrical properties and crystallinity of YBa/sub 2/Cu/sub 3/O/sub 7-x/ ultrathin films
Author :
Drozdov, Y.N. ; Nozdrin, Y.N. ; Parafin, A.E. ; Pavlov, S.A. ; Talanov, V.V. ; Varganov, A.V. ; Vopilkin, E.A.
Author_Institution :
Inst. for Phys. of Microstructures, Acad. of Sci., Nizhny Novgorod, Russia
fDate :
6/1/1997 12:00:00 AM
Abstract :
The X-ray data, DC and microwave properties as functions of the YBaCuO epitaxial films thickness in the range from 5 to 300 nm are investigated. The films were deposited by laser ablation on LaAlO/sub 3/ substrates. Films over 9 nm thickness have T/sub c0/=89 K, J/sub c/(77 K)>3 MA/cm/sup 2/ and the thickness dependence of their effective microwave surface resistance R/sub eff/ at 77 K, 10 GHz is in good agreement with the local electrodynamic theory for the thickness-independent intrinsic surface resistance R/sub s/=0.25 m/spl Omega/ and penetration depth /spl lambda/=250 nm. Decreasing a film thickness to less than a few tens nanometers provides a decrease of orthorhombicity parameter of YBCO cell, and to less than 9 nm - a reduction of transition temperature. The ultrathin films showed no degradation during thermocycling without a protection layer.
Keywords :
X-ray diffraction; barium compounds; high-temperature superconductors; penetration depth (superconductivity); pulsed laser deposition; superconducting epitaxial layers; superconducting thin films; superconducting transition temperature; surface conductivity; yttrium compounds; 10 GHz; 77 K; 89 K; 9 nm; LaAlO/sub 3/; X-ray diffraction; YBa/sub 2/Cu/sub 3/O/sub 7-x/ ultrathin films; YBa/sub 2/Cu/sub 3/O/sub 7/; crystallinity; effective microwave surface resistance; electrical properties; epitaxial films thickness; high temperature superconductor; laser ablation; local electrodynamic theory; microwave properties; orthorhombicity parameter; thermocycling; thickness-independent intrinsic surface resistance; transition temperature; Crystallization; Electrodynamics; Laser ablation; Masers; Microwave theory and techniques; Substrates; Surface resistance; Temperature; X-ray lasers; Yttrium barium copper oxide;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
