Detection of nano scale thin films with polarized neutron reflectometry at the presence of smooth and rough interfaces

TL;DR

This paper investigates how interface smoothness and roughness affect the accuracy of thin film characterization using polarized neutron reflectometry, focusing on phase determination and SLD retrieval.

Contribution

It introduces a detailed analysis of interface smoothness and roughness effects on neutron reflectometry measurements, enhancing the understanding of phase and SLD determination in realistic samples.

Findings

Smooth interfaces influence phase and SLD retrieval accuracy.

Roughness causes variations in reflection coefficients.

The study provides methods to account for interface imperfections.

Abstract

By knowing the phase and modules of the reflection coefficient in neutron reflectometry problems, a unique result for the scattering length density (SLD) of a thin film can be determined which will lead to the exact determination of type and thickness of the film. In the past decade, several methods have been worked out to resolve the phase problem such as dwell time method, reference layer method and variation of surroundings, among which the reference method and variation of surroundings by using a magnetic substrate and polarized neutrons is of the most applicability. All of these methods are based on the solution of Schrodinger equation for a discontinuous and step-like potential at each interface. As in real sample there are some smearing and roughness at boundaries, consideration of smoothness and roughness of interfaces would affect the final output result. In this paper, we have investigated the effects of smoothness of interfaces on determination of the phase of reflection as well as the retrieval process of the SLD, by using a smooth varying function (Eckart potential). The effects of roughness of interfaces on the same parameters, have also been investigated by random variation of the interface around it mean position.