Study on spin dependent tunneling and Coulomb blockade in granular systems with 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 thin insulating Co–Al–O granular film is filled, and discuss the observed Coulomb blockade with a clear threshold voltage (Vth) and the enhanced tunnel magnetoresistance of about 30% at a voltage slightly above Vth. Recent results of our scanning tunneling microscopy studies to clarify the topographic features and single electron tunneling phenomena on the surface of Co–Al–O granular films are also presented.