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Development of a Correlative Approach Between Scanning Electrochemical Cell Microscopy and Micro X-Ray Photoelectron Spectroscopy; Case Study of the Electrochemical Activity of an Indium Tin Oxide Surface

par Pasque, Corentin
Président du jury Evano, Gwilherm
Co-Promoteur Reniers, François ;Ustarroz Troyano, Jon
Publication Non publié, 2024-01-22

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Résumé :

Surface chemistry deals with the study of phenomena that occur at the surfaces or interfacesof substances, like adsorption, heterogeneous catalysis, corrosion, crystallization, dissolution,electrochemistry etc. Characterization of the surface is therefore crucial in those field of studyand analytical methods were developed in order to characterize the surface of the substrate,for example X-ray Photoelectron Spectroscopy (XPS) is a method that enable the chemicalsurface composition of a sample assuming that the surface is homogeneous.In the microscale, this assumption lead to errors as a sample that appear homogeneous in themacroscale, will often exhibit localized microscopic heterogeneity. It is therefore importantto develop analytical methods to characterize the surface at a microscopic scale.The multi-microscopy approaches have gained significant attention in recent years due to thewealth of information that can be acquired through their use. Scanning Electrochemical CellMicroscopy (SECCM) has been extensively employed in correlation with other methods aspart of a multi-microscopy approach. Scanning Electron Microscopy (SEM), TransmissionElectron Microscopy (TEM), and Atomic Force Microscopy (AFM) are examples oftechniques that have already been correlated with SECCM. However, as of now, there hasbeen no successful correlation with Microprobe X-ray Photoelectron Spectroscopy (µ-XPS).This study introduces a method for the correlation between SECCM and µ-XPS, which isthen tested using two variations: the plasma treatment method and the Physical VaporDeposition (PVD) of gold method. Both methods are subsequently applied in one-shotexperiments on Indium Tin Oxide (ITO) samples, serving as a proof of concept for eachapproach.The electrochemical system investigated for the plasma treatment method involves theoxidation/reduction of silver nanoparticles on Indium Tin Oxide (ITO) using a silver nitratesolution (electroplating reaction). In contrast, the electrochemical system examined for thePhysical Vapor Deposition (PVD) of gold method pertains to the oxidation/reduction of thegold layer that is deposited onto the ITO substrate.XPS measurements include the study of ITO, ITO modified by plasma, and ITO coated witha nanometric layer of gold, with qualitative and semi-quantitative analysis of the samples.Subsequently, measurements of µ-XPS maps of characteristic signals of the various samplesare performed.The presented plasma treatment method yields inconclusive results, and no correlationbetween SECCM and µ-XPS is achieved. This can be attributed to the complexity of thesystem and the inherent limitations of a one-shot experiment, which allows no room for errorin either the SECCM or µ-XPS measurements.On the other hand, the presented PVD of gold method demonstrates a 1-to-1 correlationbetween SECCM and µ-XPS. This success is explained by the system's simplicity incharacterization for both SECCM and µ-XPS, overcoming the limitations of the one-shotexperiment.