Scanning force microscopy was used to study localized charge deposition and subsequent transport in Co nanoclusters embedded in SiO 2 deposited on an n-type Si substrate. Co nanoclusters were charged by applying a bias voltage pulse between tip and sample, and electrostatic force microscopy was used to image charged areas, to determine quantitatively the amount of stored charge, and to characterize the discharging process. Charge was deposited controllably and reproducibly within areas ϳ20-50 nm in radius, and an exponential decay in the peak charge density was observed. Longer decay times were measured for positive than for negative charge; this is interpreted as a consequence of the Coulomb-blockade energy associated with single-electron charging of the Co nanoclusters.

No abstract

No abstract

No abstract

We have investigated the structural, magnetic, and transport properties of discontinuous CoFe/HfO2 multilayers consisting of layers of ferromagnetic particles dispersed in an insulating matrix. Negative magnetoresistance due to spin-polarized tunneling has been observed with the current both in the plane and perpendicular to the plane of the film. The properties of these films are intermediate between tunnel junctions and cermet films. They exhibit high magnetoresistance sensitivity at low fields, are easy to prepare, are very robust due to the protective oxide matrix, and are resistant to electrical breakdown. These properties can be optimized with annealing.