Diffuse neutron reflectivity and AFM study of interface morphology of an electro-deposited Ni/Cu film

TL;DR

This study compares the interface morphology of electro-deposited Ni/Cu bilayer films using neutron reflectivity and AFM, revealing distinct surface structures and providing microscopic quantification of differences between electro-deposition and sputtering techniques.

Contribution

First to microscopically quantify and compare the interface morphologies of Ni/Cu films deposited by electro-deposition and sputtering using neutron reflectivity and AFM.

Findings

Electro-deposited surface shows a quasi-two-level roughness.

Buried interface morphology can be characterized by off-specular neutron reflectivity.

Distinct differences in surface morphology between electro-deposited and sputtered films.

Abstract

We present a detailed study of the interface morphology of an electro-deposited (ED) Ni/Cu bilayer film by using off-specular (diffuse) neutron reflectivity technique and Atomic Force Microscopy (AFM). The Ni/Cu bilayer has been electro-deposited on seed layers of Ti/Cu. These two seed layers were deposited by magnetron sputtering. The depth profile of density in the sample has been obtained from specular neutron reflectivity data. AFM image of the air-film interface shows that the surface is covered by globular islands of different sizes. The AFM height distribution of the surface clearly shows two peaks [Fig. 3] and the relief structure (islands) on the surface in the film can be treated as a quasi-two-level random rough surface structure. We have demonstrated that the detailed morphology of air-film interfaces, the quasi-two level surface structure as well as morphology of the buried interfaces can be obtained from off-specular neutron reflectivity data. We have shown from AFM and off-specular neutron reflectivity data that the morphologies of electro-deposited surface is distinctly different from that of sputter-deposited interface in this sample. To the best of our knowledge this is the first attempt to microscopically quantify the differences in morphologies of metallic interfaces deposited by two different techniques viz. electro-deposition and sputtering.