Growth and Transport Properties of Tunneling Barriers in HTS devices


Gerritsma, G.J. and Verhoeven, M.A.J. and Moerman, R. and Blank, D.H.A. and Rogalla, H. (1996) Growth and Transport Properties of Tunneling Barriers in HTS devices. In: Symposium on Epitaxial Oxide Thin Films II, November 26-30, 1995, Boston, MA, USA (pp. pp. 287-296).

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Abstract:In this contribution we will discuss the charge transport of ramp-type HTS Josephson junctions with a Ga-doped PBCO barrier layer. It will be demonstrated that in these junctions charge transport takes place via tunneling processes. The Cooper pairs tunnel directly, at least for T ≤ Tc/2, whereas the quasiparticles tunnel indirectly via localized states. By substituting Cu-chain atoms with Ga-atoms the density of localized states appear to be reduced, resulting in an increase in IcRn-product. Another way to increase this product is a reduction in barrier thickness. Growth studies by AFM of PBCO barriers on ramps indicate that below about 10 nm barriers become increasingly less homogeneous, and below about 6 nm pin holes are very likely to occur. This sets a lower limit on the useful barrier thickness. Presently critical-current densities up to 104 A/cm2 at 40 K, and IlR,-products up to 10 mV at 4.2 K are easily obtained.
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Copyright:© 1996 MRS
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