  Direct measurements of the superconducting superfluid on the surface of
vacuum-cleaved Bi2Sr2CaCu2O8(BSCCO) samples are reported. These measurements
are accomplished via Josephson tunneling into the sample using a scanning
tunneling microscope (STM) equipped with a superconducting tip. The spatial
resolution of the STM of lateral distances less than the superconducting
coherence length allows it to reveal local inhomogeneities in the pair
wavefunction of the BSCCO. Instrument performance is demonstrated first with
Josephson measurements of Pb films followed by the layered superconductor
NbSe2. The relevant measurement parameter, the Josephson ICRN product, is
discussed within the context of both BCS superconductors and the high
transition temperature superconductors. The local relationship between the ICRN
product and the quasiparticle density of states (DOS) gap are presented within
the context of phase diagrams for BSCCO. Excessive current densities can be
produced with these measurements and have been found to alter the local DOS in
the BSCCO. Systematic studies of this effect were performed to determine the
practical measurement limits for these experiments. Alternative methods for
preparation of the BSCCO surface are also discussed.
