Ion-beam engineering of Co/TiO₂ multilayer nanostructures

Abstract

Multilayer structures consisting of Co/TiO₂ bilayers with partial layer thicknesses varied within several nanometers and a total thickness of up to 100 nm were obtained using the ion-beam sputter deposition method and studied using a combination of analytical techniques. It is shown that, in [Co(2 nm)/TiO₂(2 nm)]₁₅, [Co(2 nm)/TiO₂(4 nm)]₁₅, and [Co(4 nm)/TiO₂(4 nm)]₁₂ structures, the mean-square surface roughness does not exceed 0.9 nm, all partial layers are continuous, all interfaces are plane-parallel and sharp, and the characteristics of each layer are close to those of the corresponding bulk material. The [Co(2 nm)/TiO₂(4 nm)]₁₅ structure is characterized by the maximum transparency (exceeding 7% in he visible spectral range. The properties of these multilayer films are promising for applications in magnetooptics and spintronics. The surfaces of [Co(4 nm)/TiO₂(2 nm)]₁₅ and [Co(6 nm)/TiO₂(2 nm)]₁₂ structures have mean-square roughnesses above 1 nm and exhibit percolations with a surface density of up to 5 × 10⁷ cm⁻². A decrease in the partial layer thickness below 2 nm leads to the mixing of layers, while an increase in the thickness of individual TiO₂ layers above 6 nm leads to significant differences of the optical transmission spectrum from that of the anatase form of TiO₂ and to a decrease in the transparency.