  An environmentally stable mesoscopic thin film of Au of certain thickness has
been deposited thermally on top of a Ag+ implanted oxide substrate to develop a
close to room temperature superconductor. This thin film has been deposited in
two different stages. Initially, a sol-gel derived ion conducting metal oxide
(ICMO) thin film has been deposited by spin coating. Afterward, Ag+ has been
introduced inside ICMO thin film by a chemical method. Following this, a thin
layer of Au has been deposited on top of that Ag ion-implanted oxide via
thermal evaporation. The temperature dependent resistivity (R-T) has been
studied by four probe method. During high-to-low temperature sweep, around 240
K this thin film sample shows a sudden drop of resistance from 0.7 Ohm to 0.1
micro-Ohm. This 6-7 orders drop of resistance has been observed instantly
within <0.1 K temperature variation of the sample. This transition temperature
(TC) has been shifted toward the higher temperature by 5-6 degrees when
temperature has been increased from low to the higher side. During 2nd and 3rd
temperature cycling, both these transitions have been shifted by ~10 K towards
room temperature w.r.t the earlier. However, after three successive temperature
cycles, TC becomes stable and transitions occur close to 0 oC repeatedly. At
the low resistance phase, current level has been varied from +100 mA to -100 mA
which shows a random fluctuation of voltage drop within 10 nV range, indicating
resistance under such circumstance is too low to measure by Delta mode
electrical measurement (0.1 micro-Ohm). Besides, transition temperature reduces
to lower temperature by 4 K, after applying 1 tesla magnetic field
perpendicular to the thin film. Few YouTube video links of temperature
dependent electrical characterization of such a thin film is given next to the
acknowledgement section.
