Additions to "Atomistic Understanding of the Formation, Structure, and Decomposition of an Fe₄C Iron Carbide Phase on a Copper Substrate"

Having an atomistic understanding of the formation andstructuralcharacteristics of bulk and surface iron carbide phases plays a crucialrole in comprehending the mechanisms of phase transformation, microstructureformation, and surface reconstructions in the development of advancedmaterials with improved magnetic, mechanical, and catalytic properties.This study uses synchrotron (SR) and angle-resolved (AR) XPS, STM,LEED, and theoretical calculations (DFT) with the aim to provide adetailed experimental and theoretical discussion on the formation,stabilization, structure, and decomposition of Fe4C ironcarbide. FCC(100) Fe4C iron carbide multilayer films wereprepared on Cu(100) by evaporating iron in the presence of an ethyleneatmosphere. Angle-resolved XPS measurements reveal that surface andinterior carbon can be distinguished due to their appearance at differentbinding energies and reveal that the surface consists of Fe2C while the bulk has Fe4C stoichiometry. LEED and STMmeasurements show that the surface exhibits the p4g(2 x 2) clockreconstruction. Theory simulations show that the bulk Fe4C iron carbide has a constrained crystal lattice with alternatingFe and Fe4C2 layers, which grow in a pseudomorphicway on the copper. The carbide phase is stable up to 700 K. Abovethis temperature, iron diffuses into the copper while carbon remainson the surface, where it forms graphite.