A microprocessor-aided platform enabling surface differential reflectivity and reflectance anisotropy spectroscopy

Abstract

Surface differential reflectivity (SDR) and reflectance anisotropy spectroscopy (RAS) [sometimes known as reflectance difference spectroscopy] are two well-known optical spectroscopies used in the investigation of surfaces and interfaces. Their adaptability on different experimental conditions (vacuum, controlled atmosphere and liquid environment) allows for the investigation not only of surface states and/or ultra-thin films but also of more complex interfaces. In these circumstances, the analysis of the sample with both techniques is decisive in view of obtaining a correct picture of the sample optical properties. In this work, we show a microelectronic hardware solution useful to control both a SDR and a RAS apparatus. We describe an electronic architecture that can be easily replicated, and we applied it to a representative sample where the interpretation of the optical properties requires an analysis by both SDR and RAS. Graphic abstract

Porphycene Films Grown on Highly Oriented Pyrolytic Graphite: Unveiling Structure–Property Relationship through Combined Reflectance Anisotropy Spectroscopy and Atomic Force Microscopy Investigations

“…A homemade RAS setup was used for the experiments. Details of our system were reported in the literature [18]. Our optical setup works in the visible spectral range.…”

Optical Anisotropy of Porphyrin Nanocrystals Modified by the Electrochemical Dissolution

“…The RAS signal is defined as the difference in the reflectivity between α and β direc tions (𝑅 , 𝑅 ) normalized by the total reflectivity (𝑅 ): A high-sensitivity homemade RAS apparatus [5] with a light spot diameter of about 5 mm was used to collect the spectra. The light coming from a Xe arc lamp was linearly polarized (α-direction) by a Glan-Thompson optical system and passed through a Photo-Elastic Modulator (PEM), which rotates the light polarization along two mutually orthogonal directions (α and β) at a double frequency with respect to the resonance frequency of 50 kHz.…”

“…Reflectance anisotropy spectroscopy (RAS) has been widely exploited in the past in order to investigate the physical-chemical properties of organic systems featuring different solid phase aggregates and prepared using different growth techniques (Langmuir-Blodgett and Langmuir-Schaefer methods [1,2], physical vapor deposition [3,4], etc.). More specifically, RAS offers the possibility of studying systems that exhibit anisotropies (down to a signal intensity of 10 −6 [5]) related to the electronic or morphological characteristics of the organic layer, even if it is grown onto an isotropic substrate such as graphite [6]. For instance, this optical spectroscopy has been successfully used to characterize complex 3D nanoarchitectures based on porphyrins layers in order to understand the mechanisms governing their interaction with the environment (i.e., vacuum or vapors), in view of their implementation in organic-based devices and sensors [7][8][9].…”