Structure and stability of 2.4 nm period amorphous Ni–Nb/C multilayers

Amorphous Ni–Nb/C multilayers with a period of 2.4 nm were prepared by pulsed laser ablation deposition. The as-deposited multilayers were found to have an interdiffused Ni1/3Nb1/3C1/3 layer present at the two interfaces; Ni1/2Nb1/2/C and C/N1/2Nb1/2. The specular reflectivity and diffuse scattering studies show that the interface roughness is chemical and not morphological in origin. The structural studies performed using X-ray scattering techniques after a period of 2.5 years from deposition show that the behaviour does not change with time. These results indicate that the multilayered structure is temporally stable in spite of the strong composition dependent driving force for chemical homogenization. The structural stability against homogenization is due to the presence of an amorphous Ni1/3Nb1/3C1/3 layer present at the interfaces which acts as a diffusion barrier.