Berreman effect in infrared absorption spectroscopy of ionic oxide coatings formed by atomic layer deposition on three-dimensional structures

Abstract

We show through modeling and experimentation that the Berreman effect, physically manifested and investigated on planar surfaces for more than four decades, can be readily realized and studied in three-dimensional nonplanar structures. The Berreman effect is also used as a nonlocal probe to evaluate topography and homogeneity of insulating ionic oxide layers in nonplanar geometries. During infrared transmission studies the macroscopic angular dependence of the longitudinal optical mode absorbance deviates from that observed in the planar case, and the angular dependence is shown to be physically linked to geometry and homogeneity of the ionic oxide layer. Spectroscopic modeling confirms the observations on the angular dependence of longitudinal optical mode absorbance on various nonplanar systems. A linear combination of [sin(θ)]4 with appropriate coefficients is found to describe the trend of longitudinal optical mode absorbance in nonplanar structures.