Bismuth layer properties in the ultrathin Bi-FeNi multilayer films probed by spectroscopic ellipsometry

TL;DR

This study uses spectroscopic ellipsometry to analyze ultrathin Bi-FeNi multilayer films, revealing that the Bi layer can exhibit surface metallic conductivity influenced by the FeNi layer's morphology and magnetic properties.

Contribution

It introduces a spectroscopic ellipsometry method to characterize Bi layer properties in ultrathin multilayers and links surface conductivity to the FeNi layer's nanoisland structure.

Findings

Bi layer can have surface metallic conductivity

Conductivity is affected by FeNi nanoisland morphology

Ellipsometry enables detailed dielectric function analysis

Abstract

Using wide-band (0.5-6.5 eV) spectroscopic ellipsometry we study ultrathin [Bi(0.6-2.5 nm)-FeNi(0.8,1.2 nm)]N multilayer films grown by rf sputtering deposition, where the FeNi layer has a nanoisland structure and its morphology and magnetic properties change with decreasing the nominal layer thickness. From the multilayer model simulations of the ellipsometric angles, Psi(omega) and Delta(omega), the complex (pseudo)dielectric function spectra of the Bi layer were extracted. The obtained results demonstrate that the Bi layer can possess the surface metallic conductivity, which is strongly affected by the morphology and magnetic properties of the nanoisland FeNi layer in the GMR-type Bi-FeNi multilayer structures.