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
Highlights
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
We describe an electronic architecture that can be replicated, and we applied it to a representative sample where the interpretation of the optical properties requires an analysis by both SDR and RAS
With the aim of offering the possibility to build up versatile SDR and RAS systems to researchers involved in the investigation of the optical properties of stratified films, buried and solid–liquid interfaces, we show and discuss an electronic architecture that can be replicated and used in laboratory
Summary
RAS was successfully applied on similar systems explored by SDR but, with respect to the latter, on more complex organic films [33, 34], solid–liquid interfaces [35, 36] or for volatile compounds detection [37] Both SDR and RAS spectra can be interpreted within the three-layer model, which considers the surface, or a film grown onto a substrate, as an absorbing layer with its own dielectric constant [38]. To prove the opportunity of comparing SDR and RAS spectra, we present an analysis of the optical properties of an emblematic system: meso-tetraphenyl porphyrin (H2TPP) thin film grown on highly oriented pyrolytic graphite (HOPG) In this system, RAS reveals an apparently anomalous redshift of the main porphyrin optical transition. Page 3 of 13 421 be explained and rationalized in terms of a proper combination of unpolarized and polarized SDR measurements
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