Critical-point model dielectric function analysis of WO$_3$ thin films deposited by atomic layer deposition techniques

TL;DR

This study analyzes the dielectric function of WO3 thin films grown by atomic layer deposition using spectroscopic ellipsometry and critical-point modeling, comparing experimental data with theoretical band structure calculations.

Contribution

It introduces a detailed critical-point model dielectric function analysis for WO3 thin films and correlates experimental optical data with density functional theory calculations.

Findings

Determined the complex dielectric function of WO3 across 0.72-8.5 eV.

Identified critical-point contributions matching band structure features.

Compared surface roughness effects from AFM and ellipsometry.

Abstract

WO3 thin films were grown by atomic layer deposition and spectroscopic ellipsometry data gathered in the photon energy range of 0.72-8.5 eV and from multiple samples was utilized to determine the frequency dependent complex-valued isotropic dielectric function for WO3. We employ a critical-point model dielectric function analysis and determine a parameterized set of oscillators and compare the observed critical-point contributions with the vertical transition energy distribution found within the band structure of WO3 calculated by density functional theory. We investigate surface roughness with atomic force microscopy and compare to ellipsometric determined effective roughness layer thickness.