Study on spin dependent tunneling and Coulomb blockade in granular systemswith restricted tunneling paths

We describe the microfabrication process of a granular nanobridge structure consisting of electrodes separated by a nanometer-sized gap in which a thi n insulating Co-Al-O granular film is filled, and discuss the observed Coul omb blockade with a clear threshold voltage (V-th) and the enhanced tunnel magnetoresistance of about 30% at a voltage slightly above V-th. Recent res ults of our scanning tunneling microscopy studies to clarify the topographi c features and single electron tunneling phenomena on the surface of Co-Al- O granular films are also presented. (C) 2001 Elsevier Science B.V. All rig hts reserved.