  Typically, topological superconductivity is reachable via proximity effect by
a direct deposition of superconductor (S) on top of a topological insulator
(TI) surface. Here we observed and analyzed the double critical current in the
Josephson junctions based on the topological insulator in the fabricated planar
Superconducting Quantum Interference Device. By measuring critical currents as
a function of temperature and magnetic field, we show that the second critical
current stems from the intrinsic superconductivity of the S/TI interface, which
is supported by the modified Resistively Shunted Junction model and
Transmission Electron Microscopy studies. This complex structure of the
interface should be taken into account when technological process involves
Ar-plasma cleaning.
