In situ controlled fabrication of stacks of high-Tc intrinsic Josephson junctions

Stacked series arrays of intrinsic Josephson (IJ) tunnel junctions have been fabricated on the surfaces of Bi2Sr2CaCu2O8+δ single crystals using photolithography and Ar-ion milling together with in situ monitoring of the resulting current–voltage (I–V) characteristics. The number of unit-cell-sized junctions in the stack (along the c-axis) may be varied from 1–5 to ∼200 in a controlled way. The c-axis resistivity ρc, estimated from the resistance of an individual tunnel junction is ≈30 Ω cm at 90 K. The temperature dependence ρc(T)∝ exp(Λ/T) with Λ≈43 meV, suggesting thermally activated hopping mechanism of transport in the c-axis direction.