▎ 摘　　要

The intercalation of different metals underneath the graphene sheet has opened the possibility of preparing new low-dimensional structures that could present quantum-size effects. Knowing the surface crystallograpy of these low-dimensional systems is mandatory for a complete understanding of their physical and chemical properties. In this work, we present a combined low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy, and first-principles calculations study of the structural properties of graphene-protected Fe films on Ni(111). The results indicate that graphene interacts strongly with the topmost Fe atoms, similar to graphene on Ni(111). For one and two Fe monolayer films, the Fe is isostructurally deposited on Ni (fcc on fcc), and graphene is deposited commensurably with the underlying Fe surface atoms. For one Fe monolayer case, the LEED data indicate the coexistence of two types of crystalline domains, named top-fcc and bridge-top structures. Our first-principles calculations show that for the graphene/Fe/Ni system, the total energies of the the top-fcc and bridge-top structures are nearly degenerate, consistent with the observed bistability.