Toward Complete Exfoliation of the Chemisorbed Two-Dimensional Iron Silicates on Ru(0001) via Hydrogenation

Two-dimensional (2D) transition-metal silicates are interesting materials because of their potential ferromagnetism together with their inherent piezoelectric response to their structural symmetry. Substrate-assisted bottom-up synthesis of these materials offers flexibility in their chemical composition. However, synthesizing free-standing layers has been challenging because of strong overlayer-substrate interactions which hinder exfoliation of the overlayer. Here, using density functional theory calculations, we systematically investigate the hydrogenation of such overlayers as a way to decrease the substrate-overlayer interactions. Using the Fe2Si2O8·O/Ru(0001) structure as our starting point, we study hydrogenation levels up to Fe2Si2O9H4/Ru(0001). Structural and thermodynamic properties are studied at different hydrogenation levels to describe the conditions under which exfoliation of the Fe silicate is feasible. Simulated binding energies of core electrons show that Fe is primarily in the 3+ state throughout the hydrogenation process. Simulated reflection adsorption infrared spectroscopy (RAIRS) yields distinctive shifts in vibrational peaks with increasing hydrogenation which can guide future experiments.