Multifunctional Co-C nanocomposite thin films

Nanocomposite cobalt-carbon (Co-C) thin films with a Co concentration ranging from 26 to 63 at.% were synthesized using a dual electron beam evaporation system. Transmission electron microscopy observations showed that the as-deposited films were nanocomposites consisting of nanocrystalline Co particles encapsulated in an amorphous C matrix. The spherical Co nanoparticles had a grain size between 2 and 5 nm depending on Co concentration. Magnetic properties were measured using a superconducting quantum interference devices magnetometer, which inferred that the Co-C films with a high Co content had a high saturation magnetization and low coercivity. Co-C films with a low Co content exhibited coercivity only at low temperature (10 K). The (magneto) transport properties of the Co-C films were also investigated. Additionally, nanomechanical and tribological. properties were evaluated by nanoindentation and pin-on-disc experiments, respectively. Addition of C into the films was found to significantly improve the mechanical and tribological properties. Nanocomposite Co-C films can meet several requirements (electromagnetic, mechanical, tribological, etc.) and thus are multifunctional and have potential for demanding technological applications (such as microdevices and sensors). (C) 2002 Elsevier Science B.V. All rights reserved.