Resistance and 1/f noise between circular contacts on conductive thin films

Abstract

There is a need to characterize the quality of contacts and the noise properties of new materials deposited or grown as thin films. Poor contacts are interface dominated. Perfect contacts have a negligible interface contribution and there is only a resistance and noise contribution from outside the contact region. The presence of current crowding enhances the resistance and noise contribution. Such contacts are called constriction dominated contacts. The conductive film is characterized by its sheet resistance and normalized conductance fluctuations for a unit surface. The resistance and noise is studied between two circular top electrodes of the same diameter on the conductive. To distinguish between perfect and poor contacts and to characterize the thin film in case of good contacts, we need a set of contacts with different diameters. Models for perfect and poor contacts are investigated. The scaling of resistance and noise with contact radius r is for interface dominated poor contacts: R i 1/ r 2 and S Ri 1/ r 6 . In contrast, perfect contacts with contact diameter (2 r ) much smaller than the distance between the centers (2 b ) show: R c ln( b / r ) and S Rc 1/ r 2 . From the resistance and noise measurements between constriction dominated perfect contacts, the sheet resistance and normalized noise of the thin film are calculated.