A step-by-step workflow to account for linear polarization artifacts in circular dichroism of thin films

Abstract

Circular Dichroism (CD) spectroscopy has evolved from a purely solution based method towards an important tool in the analysis of chiral thin films. Although a straightforward technique, the true CD signal is often accompanied by artifacts arising from optical anisotropy and instrumental imperfections. Here, we present a two-step workflow that separates the orientation invariant CD response for anisotropic thin films by combining az-imuthal sample rotation with sample flipping. For this purpose, a home-built sample stage was developed, which enables systematic suppression of many anisotropy-induced artifacts in commercial CD spectrophotometers. Both a detailed description of the setup itself as well as the required python script are provided. The reliability of the workflow is demonstrated on two selected samples from different research fields: chiral molecules attached to metallic surfaces as well as low-dimensional metal halide perovskites incorporating chiral spacer molecules.