E-ALD: Tailoring the Optoeletronic Properties of Metal Chalcogenides on Ag Single Crystals

Abstract

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.

Successes and Issues in the Growth of Moad and MoSe2 on Ag(111) by the E-ALD Method

“…To this aim, a potential of −1.6 V was applied to the working electrode for 1 minute, then, after the injection of a fresh buffer solution in the cell, a potential of −0.1 V was applied for 1 minute. Both the distribution valve and the cell were designed and realized in the workshop of the Applied Electrochemistry Lab of the University of Florence [10]. The potentials reported in this paper are referred to the Ag/AgCl (saturated KCl) reference electrode.…”

“…for 1 minute. Both the distribution valve and the cell were designed and realized in the workshop of the Applied Electrochemistry Lab of the University of Florence [10]. The potentials reported in this paper are referred to the Ag/AgCl (saturated KCl) reference electrode.…”

“…One of the most common SLR in electrochemistry is the under potential deposition (UPD) [7,8]. When the E-ALD outcome is a strictly epitaxial film, the technique is named electrochemical atomic layer epitaxy (ECALE) [9,10]. Indeed, the E-ALD method enables the growth of monolayers of different elements, one above the other through, the alternate deposition of an atomic layer under the surface limited constraints ensured by the exploitation of the SLRs.…”