Nucleation Behavior of SnS2 on Thiol Functionalized SAMs During Solution-Based Atomic Layer Deposition

Abstract

Solution-based atomic layer deposition (sALD) is an emerging technique that transfers the principle of traditional atomic layer deposition (ALD) from the gas phase into a wet chemical environment. This new preparation technique has new and unique properties and requirements. A large number of new surfaces and reactants are available to produce active 2D materials.

In this work a reproducible procedure to coat silicon wafers with a densely packed monolayer of (3-Mercaptopropyl)trimethoxysilane (MPTMS) molecules is presented. These highly functionalized surfaces can be used to seed the nucleation of SnS₂ in a solution-based ALD procedure. A coating routine for the production of SnS₂ is adapted from ALD to sALD and insight into the nucleation behavior of the reactands is given. X-ray reflectometry (XRR) is used to resolve the nucleation process of SnS₂ on an MPTMS self assembled monolayer (SAM) during the first three cycles of an sALD procedure. The comparison of ex situ XRR, in situ XRR, grazing incidence wide-angle X-ray scattering (GIWAXS), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX) measurements, and density functional theory (DFT) calculations find that SnS₂ first forms a closed layer and then continues to grow in islands on thiol functionalized silane SAMs. Subsequent coating cycles will continue the growth of the islands laterally and in height.