Structural and magnetic properties of hybrid ferromagnetic metal/semiconductor (ZnTe)/Co core-shell nanowires

We report on the study of two-step grown crystalline II-VI semiconductor nanowires (NWs) covered with ferromagnetic metal. In the first step ZnTe nanowires were grown by a vapor-liquid-solid mechanism (VLS) on GaAs (1 1 1)B substrates covered with Au thin film. Solid source molecular beam epitaxy and Au-based nanocatalysts were used for these purposes. The nanowires were smooth, slightly tapered and mostly oriented along the axis perpendicular to the substrate. The diameters of the obtained nanowires were from 30 to 70 nm and their length was around 1 µm. In the second step the nanowires were covered with Co shell of different thicknesses. As a result magnetic nanotubes were formed. Structural characterization of the nanowires was performed using scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy techniques. Initial roughness of the nanowires influences the growth of Co shell with the increment of deposition thickness. Deposited Co formed nanograins having hexagonal closed packed structure, however face cubic centered grains were also observed. Magnetic force microscopy experiments on an individual Co nanotube revealed magnetic anisotropy of the investigated structures.