Periodic Coulomb blockade oscillations observed in single-layered Fe nanodot array

Abstract

Clear Coulomb blockade characteristics of Fe nanodots in a multiple-nanodot array were achieved. The array was fabricated in a self-assembled manner by Fe deposition between the source and drain electrodes on thermally-grown SiO2/Si substrates. Current oscillations as a function of gate voltage were observed in almost all the devices having an average Fe film thickness (1.8–2.8 nm) less than the threshold thickness showing metallic conduction. The oscillations in major cases were complex owing to contributions from many dots; periodic current oscillations, apparently arising from a single dot, were seen with a certain probability (approximately 10%) at the Fe film thickness range from 2.4 to 2.8 nm which was close to the thickness showing metallic conduction. The periodic oscillations were analyzed by considering the Fermi–Dirac distribution function and this simple oscillation appeared from a certain single dot that existed among many other dots contributing to the background current. The phase of the oscillation period occasionally shifted. This phenomenon is explained by a single-electron charging effect from another dot far away from the single dot under consideration.