Coulomb blockade phenomena and impedance spectroscopy studies in a double-barrier junction

An electrical junction was fabricated in sandwich configuration from a nano- SnO2 film with a grain size of thickness 0.83 mm. The sandwich junction consisted of one monolayer between two copper electrodes. At room temperature, the Cu/nano- SnO2/Cu arrangement shows current steps similar to those of a Coulomb blockade, and a Coulomb staircase I – V characteristic with asymmetric behavior, which makes it a promising candidate for use in future room-temperature single-electron transistors. While the zero-conductance gap is due to the Coulomb blockade, in good agreement with semi-classical theory, the step–plateau behavior with asymmetry in the voltage spacing and current increase can be attributed to an effect from internal energy levels. Single-electron tunneling is assumed to proceed through a double tunnel barrier junction. Impedance spectroscopy was also performed within a wide frequency range from 1 Hz to 1 MHz.