  Stacks of a few intrinsic tunnel junctions were micro-fabricated on the
surface of Bi-2212 single crystals. The number of junctions in a stack was
tailored by progressively increasing the height of the stack by ion-beam
etching, while its tunneling characteristics were measured in-situ in a vacuum
chamber for temperatures down to ~13 K. Using this in-situ etching/measurements
technique in a single piece of crystal, we systematically excluded any spurious
effects arising from variations in the junction parameters and made clear
analysis on the following properties of the surface and inner conducting
planes. First, the tunneling resistance and the current-voltage curves are
scaled by the surface junction resistance. Second, we confirm that the
reduction in both the gap and the superconducting transition temperature of the
surface conducting plane in contact with a normal metal is not caused by the
variation in the doping level, but is caused by the proximity contact. Finally,
the main feature of a junction is not affected by the presence of other
junctions in a stack in a low bias region.
