Properties and applications of cobalt-based material produced by electron-beam-induced deposition

Abstract

The deposition of cobalt-containing material from dicobalt octacarbonyl using a focused electron beam is reported. The material contains between 30% and 50% (atomic) cobalt, with the balance being carbon and oxygen, and comprises nanocrystalline metallic grains embedded in a carbonaceous matrix. Arches bridging two electrodes were fabricated to allow current–voltage (I–V) measurements to be conducted. The material resistivity decreases strongly with the deposition beam current, with values as low as 45 μΩ cm being attainable. Material growth by indirect irradiation is found to give rise to material of high resistivity and can result in highly resistive arches. At low temperatures, three distinctive conduction regimes are observed, with the I–V characteristics flattening out at the origin. At 20 K step-like features suggestive of Coulomb- blockade effects were observed. Magnetic force microscope (MFM) images of the material indicates that it is ferromagnetic in nature. The application of the technique and material to fabricate MFM tips is demonstrated. The use of selective material deposits as catalyst sites for the growth of carbon nanotubes is also demonstrated.