We have measured point contacts with a gold tip on Bi2Sr2CaCu2O8+y thi
n films and Bi2Sr2CaCu2O8+y/SrTiO3 double layers. The results show tun
neling or direct conductivity behaviour depending on the junction para
meters and can be fitted by corresponding theoretical models. From fit
ting procedure of differential characteristics by modified Blonder-Tin
bham-Klapwijk (BTK) theory the Fermi velocity v(F) = 5 x 10(5) m/s, ra
tio 2 Delta(4.2K)/kT(c) = 7.9 and coherence length xi(ab) = 3.5 mm wer
e obtained. The changing of the interface transmission by additional l
ayers of different thickness corresponding to metallic or insulating b
ehaviour is shown. In the frame of the inelastic scattering of quasipa
rticles the linear background of differential conductance is discussed
.