I-V characteristics of single and clustered ligand stabilized cobalt nanoparticles on highly oriented pyrolytic graphite obtained with conducting atomic force microscopy under ambient conditions

Fetting J, Mill N, Hütten A, Reiss G, Peter MK-H, Mattay J. I-V characteristics of single and clustered ligand stabilized cobalt nanoparticles on highly oriented pyrolytic graphite obtained with conducting atomic force microscopy under ambient conditions. Journal Of Applied Physics. 2012;112(10): 104327.Cobalt nanoparticles are of large interest for applications in magnetic devices and in healthcare. We studied their properties by conducting atomic force microscopy on clusters of particles and single particles deposited on highly oriented pyrolytic graphite. Topography and conductance maps have been taken simultaneously and I-V curves were measured at predefined locations on nanoparticle clusters and single nanoparticles. The I-V curves on clusters corresponded to an energy band gap in the density of states of 3.7 eV which matches the band gap of CoO nanostructures while a single particle showed only a gap of 1.3 eV in the I-V curves which is similar to the indirect band gap of Co3O4. Moreover, we found a resistive switching, i.e., a change of the clusters' resistance during sweeping the voltage. As a reason, we suggest a transition from CoO to Co3O4 due to heating effects. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4766754