Abstract
The interest in the research of the structural and electronic properties between graphene and lithium has bloomed since it has been proven that the use of graphene as an anode material in lithium-ion batteries ameliorates their performance and stability. Here, we investigate an alternative route to intercalate lithium underneath epitaxially grown graphene on iridium by means of photon irradiation. We grow thin films of LiCl on top of graphene on Ir(111) and irradiate the system with soft X-ray photons, which leads to a cascade of physicochemical reactions. Upon LiCl photodissociation, we find fast chlorine desorption and a complex sequence of lithium intercalation processes. First, it intercalates, forming a disordered structure between graphene and iridium. On increasing the irradiation time, an ordered Li(1 × 1) surface structure forms, which evolves upon extensive photon irradiation. For sufficiently long exposure times, lithium diffusion within the metal substrate is observed. Thermal annealing allows for efficient lithium desorption and full recovery of the pristine G/Ir(111) system. We follow in detail the photochemical processes using a multitechnique approach, which allows us to correlate the structural, chemical, and electronic properties for every step of the intercalation process of lithium underneath graphene.
Highlights
Graphene (Gr) has been extensively studied over the past decade,[1] and there is a significant amount of works regarding the intercalation of small molecules or atoms in graphitic-like nanostructures.[2−4] In particular, the intercalation of alkali metals under epitaxial graphene has been widely studied[5−7] since it is a possible route to tailor the graphene band structure and doping level
A combined characterization with Low Energy Electron Microscopy (LEEM), X-ray photoemission spectroscopy (XPS), and μ-ARPES allows us to follow every step of the intercalation process in real time
We show that upon photon exposure, LiCl dissociates, chlorine atoms desorb, and lithium intercalates graphene
Summary
Graphene (Gr) has been extensively studied over the past decade,[1] and there is a significant amount of works regarding the intercalation of small molecules or atoms in graphitic-like nanostructures.[2−4] In particular, the intercalation of alkali metals under epitaxial graphene has been widely studied[5−7] since it is a possible route to tailor the graphene band structure and doping level. Alternative routes allowing the intercalation of lithium underneath graphene as well as a detailed description at the atomic level of the structures formed during the intercalation processes may be of interest in the field. The combined use of diffracted low-energy electrons and photoelectrons allows us to follow in real time the chemical, structural, and electronic processes occurring during lithium intercalation through graphene.
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