The temperature dependence of electric conductivity and current - voltage characteristics were studied in CuO single crystals with Cu films deposited onto natural faces by thermal evaporation in vacuum or electrolysis. After electric (resistive) or thermal annealing of the samples, the conductivity of Cu films in this system significantly increases (by a factor of tens, hundreds and up to 1.5 * 10⁵ and above) as compared to that of the control Cu films on a glass-ceramic substrate. The effect is attributed to an interfacial layer formed between CuO and Cu, the high conductivity mechanism in which is unclear. The thickness estimation of a layer gives a value about 100 Angstrom. So the ratio may be up 6 x 10⁶ and above at T=293 K. It is suggested that the giant electric conductivity and its HTSC-like temperature dependence as well as nonlinear current - voltage characteristics of the samples can be due to the formation of superconducting regions with the critical temperatures significantly higher than 400 K. For this case the critical current density at the interfase may be as high as 10⁷ - 10⁸ A/cm².

This work is partually supported by the program 40.012.1.1.1153 - 14/02 "Magnetoelectronics" and RFBI (project-2001-Ural N 01-02-96429).

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