Two-Dimensional Semiconductors Thin Films of MoS2 and MoSe2 on Ag(111)

Abstract

In the recent years, technological development in the fields spanning from nanoelectronics to new solar energy materials, requires highly controlled nanostructured surfaces, ultra-thin films and 2D structured materials. The Electrochemical Atomic Layer Deposition (E-ALD) is one of these techniques that allows us to produce thin films of semiconductor. Exploiting Surface Limited Reactions (SLR), it enables the deposition of highly ordered ultra-thin films from diluted aqueous solutions and at room temperature and pressure. Underpotential deposition (UPD) is a type of electrochemical SLR, where an atomic layer of a first element is deposited on a second, at a potential prior to (under) that needed to deposit the first element on itself, so that the resulting deposit is generally limited to an atomic layer. It occurs when the depositing element is able to somehow interact with the substrate, so that the deposition of the layer in direct contact with the substrate occurs at a potential preceding bulk deposition, that is, the deposition of the element on itself. MoS2 and MoSe2 are important transition metal dichalcogenides (TMDs). E-ALD method was used to obtain semiconductor compounds in the form of thin films. UPD anodic electrodeposition of Na2S and Na2SeO3 on crystalline Ag[111] electrode are well-known. The research move to discover the optimal conditions to deposit Mo on Ag/S and on Ag/Se from a solution of MoO4 2- in alkaline buffer. This study has been carried by means of voltammetric techniques, XPS and AFM characterizations of the deposit.