Investigation of thermally evaporated nanocrystalline thin cobalt films

Abstract

structures are of large importance. From the practical point of view, they are very significant for tailoring of the specimens with the required properties. In particular, they allow to develop high-density magnetic and magneto-optic recording media, modern recording heads, high-performance permanent magnets, magnetic sensors, and transformer steel sheets [1,2]. The knowledge of the magnetic domain behavior in relation to the morphological structure of the specimens is also important for theoretical modeling of magnetic properties [1,2].Thin magnetic films attract large attention from the fundamental as well as technological point of view. On the fundamental side, they exhibit different magnetic properties, such as magnetic anisotropy [3], magnetic microstructure [4], coercivity [5], and magnetoresistance [6], depending on their thickness, composition, crystalline structure, and preparation conditions. From the technological point of view, thin magnetic films have a number of applications; for example, they are used in magnetic information storage media, magneto-optic recording media, magnetic devices, and sensors [1,2].In particular, cobalt thin films have been the subject of wide and intense study in recent years. They can be prepared by various techniques, for example by sputtering, thermal evaporation, electron beam evaporation, molecular beam epitaxy, pulsed laser deposition, electrodeposition, and chemical vapor deposition [7][8][9]. The obtained films are usually nanocrystalline in nature and possess specific, improved mechanical, physical, magnetic, and chemical properties in comparison with conventional microcrystalline counterparts. Depending on the film thickness as well as the preparation method and conditions used, cobalt thin films exhibit a wide range of morphological and magnetic properties, and especially various magnetic domain structures with inplane and outofplane magnetization [10][11][12][13]. AbstractIn this paper, a study has been made of nanocrystalline thin cobalt films with thicknesses in the range from 10 to 60 nm. The films were thermally evaporated at incidence angle of 0° in a vacuum of about 10 − 5 mbar. The morphological structure of the films consists of nanocrystalline grains regular in shape and densely packed. As the film thickness is increased from 10 to 60 nm, the average grain size increases from 22.0 to 28.9 nm. The films crystallize mainly in the hexagonal close-packed phase of cobalt. The magnetic structure is composed of domains. In films with thicknesses in the range from 10 to 40 nm, the domains are magnetized in the plane of the film, while films with thicknesses of 50 and 60 nm possess both inplane and perpendicular magnetization components. The domains with inplane magnetization are irregular in shape and typically from a few to 10 mm in size, whereas the domains with perpendicular magnetization form a fine maze stripe pattern of the order of 100 nm in width.

Cobalt-Activated Transfer-Free Synthesis of the Graphene on Si(100) by Anode Layer Ion Source

“…Several factors were taken into account choosing the temperature during a hydrocarbon ion beam irradiation. In the case of the graphene synthesis by annealing the amorphous carbon and catalytic metal bilayer, a higher carbon film deposition temperature is benefi- Roughness and grain size increase with Co film [48]. For metal-induced crystallization of the silicon, the smaller metal grains result in a faster layer exchange process [49].…”