STRONTIUM CONCENTRATION-DEPENDENCE OF THE INPLANE PENETRATION DEPTH OF SUPERCONDUCTING LA2-XSRXCUO4+ -DELTA VERY THIN-FILMS/

Using a Molecular Beam Epitaxy deposition technique, c-axis oriented L a2-xSrxCuO4+/-delta thin films (50nm thick) were prepared on (001) SrT iO3 substrates. Measurements of the ac sheet impedance Z = R + iwL(k) performed with a two coil mutual inductance technique were used to det ermine the temperature dependent in-place penetration depth lambda(ab) (T) of the layers for various values of their Sr content x. Values of lambda(ab)(0) deduced from the kinetic inductance L(k)(T) and from the vortex pinning activation energy Delta U show an increase of lambda(a b)(0) with growing carrier density n in the overdoped regime in sharp contrast with the simple London's prediction lambda(ab)(-2)(0) similar to n.