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Zoldan V.C.,Federal University of Santa Catarina | Cruz J.S.,Federal University of Santa Catarina | Munford M.L.,University Of Viosa | Zangari G.,University of Virginia | And 2 more authors.
Journal of the Electrochemical Society | Year: 2010

We report on the morphology, magnetic properties, and magnetoresistance (MR) of Fe thin films in the as-deposited state and after subsequent oxidation in water vapor or CO/ CO2 atmospheres. The Fe layers were electrodeposited on hydrogen-terminated Si single-crystal substrates from aqueous electrolytes containing iron sulfate at pH 2.3. Granular Fe films with morphological characteristics dependent of the deposition potential showed coercive fields decreasing with increasing thickness. Negative MR was observed in both configurations of current parallel or perpendicular to an in-plane magnetic field. This indicates that the as-deposited granular films already contain an oxide barrier at the grain boundaries leading to an MR that overcomes the anisotropic parts of it. Oxidation in water vapor and CO/ CO2 atmospheres resulted in samples with magnetoresistive effects in the range of 1.0-1.2%, about a factor of 4 higher than the values observed for the as-deposited Fe layers. The negative MR in both directions of the as-deposited and oxidized samples had in common the highest values at the coercive field, characteristic of systems with MR due to the field-induced alignment of adjacent grains. © 2009 The Electrochemical Society.

Garcia N.,Laboratorio Of Fisica Of Sistemas Pequeos Y Nanotecnologia | Garcia N.,University of Leipzig | Yan Z.,Laboratorio Of Fisica Of Sistemas Pequeos Y Nanotecnologia | Ballestar A.,Laboratorio Of Fisica Of Sistemas Pequeos Y Nanotecnologia | And 3 more authors.
Journal of Physics Condensed Matter | Year: 2010

The electrical potential on the surface of ∼300nm thick SiO2 grown on single-crystalline Si substrates has been characterized at ambient conditions using electric field microscopy. Our results show an inhomogeneous potential distribution with fluctuations up to ∼0.4V within regions of 1μm. The potential fluctuations observed at the surface of these usual dielectric holders of graphene sheets should induce strong variations in the graphene charge densities and provide a simple explanation for some of the anomalous behaviors of the transport properties of graphene. © 2010 IOP Publishing Ltd.

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