Spanning from nanoelectronics to new solar energy materials, technological development in the recent years requested highly controlled nanostructured surfaces, ultra-thin films, and 2D structured materials. In general, although very favorable from a full life cycle assessment (FLCA) standpoint, electrodeposition hardly allows to obtain the high order required by recent technologies. In particular cases, the electrodeposition enables the deposition of atomic layers by means of surface limited reactions (SLRs). By exploiting SLRs, it is possible to define layer-by-layer deposition scheme of different atomic layers; we refer to these schemes as electrochemical atomic layer deposition (E-ALD) and when the growth of the film is epitaxial with the substrate, the techniques are called electrochemical atomic layer epitaxy (ECALE). Aiming at characterizing structure and growth of materials grown by means of E-ALD, surface analysis techniques apply better. In particular, surface X-ray diffraction (SXRD) with high brilliance synchrotron sources enables the operando structural analysis in electrochemical environment. In recent years, several works on the operando surface characterization by means of SXRD have been reported. Thanks to novelties in the field of operando SXRD experiments, semiconducting systems were studied, such as single and multilayer of CdS and Cu2S.
Technological development in nanoelectronics and solar energy devices demands nanostructured surfaces with controlled geometries and composition. Electrochemical atomic layer deposition (E-ALD) is recognized as a valid alternative to vacuum and chemical bath depositions in terms of growth control, quality and performance of semiconducting systems, such as single 2D semiconductors and multilayered materials. This chapter is specific to the E-ALD of metal chalcogenides on Ag single crystals and highlights the electrochemistry for the layer-by-layer deposition of thin films through surface limited reactions (SLRs). Also discussed herein is the theoretical framework of the under potential deposition (UPD), whose thermodynamic treatment open questions to the correct interpretation of the experimental data. Careful design of the E-ALD process allows fine control over both thickness and composition of the deposited layers, thus tailoring the optoelectronic properties of semiconductor compounds. Specifically, the possibility to tune the band gap by varying either the number of deposition cycles or the growth sequence of ternary compounds paves the way toward the formation of advanced photovoltaic materials.
Part of the book: Semiconductors