Transforming structural and electronic properties of borophene via lithiation

Since its experimental discovery, borophene — a flat, two-dimensional material composed only of boron atoms — has emerged as one of the most intriguing additions to the rapidly expanding family of atomically thin materials. Unlike more established two-dimensional systems, borophene exhibits exceptional electronic properties arising from its unusual atomic structures, metallic character, and structural flexibility. These characteristics make it a promising candidate for future technologies, including next-generation nanoelectronic devices, sensors, and energy-storage systems. However, despite growing interest in borophene, many fundamental questions remain regarding how its properties can be controlled and modified through chemical interactions with other elements. In particular, the behavior of borophene upon interaction with alkali metals, such as lithium, is of great importance. Alkali-metal doping is widely used as a method to tune the electronic properties of two-dimensional materials, while lithium plays a central role in modern energy-storage technologies. Understanding whether lithium atoms remain on the surface, penetrate through the material, or induce structural changes is therefore essential both for fundamental research and for potential applications. 

In a study published in ACS Nano, highlighted as the journal’s front cover feature, a team of researchers from the Institute of Physics in Zagreb, Elettra Sincrotrone Trieste, Shimane University, and the Institute of Science Tokyo investigated the adsorption of lithium on epitaxial borophene grown on an iridium substrate, uncovering new details about the interfacial interactions occurring between the adspecies and the film. By combining high-resolution microscopy and spectroscopy methods available at the Nanospectroscopy beamline of the Elettra synchrotron, with state-of-the-art theoretical modelling, the team obtained a detailed picture of the atomic-scale processes occurring during lithium deposition. The multi-method capability of the Spectroscopic Photoemission and Low Energy electron Microscope (SPELEEM) at the beamline, enabling high-lateral-resolution real-space and diffraction imaging together with spectroscopy, was key for obtaining a complete picture of the investigated system.

The experiments revealed that lithium atoms deposited on borophene remain primarily on the borophene surface and do not intercalate underneath it. At the same time, lithium strongly interacts with the boron layer by transferring a substantial amount of electronic charge to the film. This charge donation significantly modifies the electronic structure of borophene (Fig. 1a and b) and also influences the atomic structure of borophene itself (see Fig. 1c and d), leading to measurable distortions of its lattice. These observations highlight the sensitive interplay between the electronic and structural properties that govern the stability of epitaxial borophene. Upon thermal treatment, a fraction of the lithium atoms leaves the surface, while the remaining lithium species participate in the formation of new boron–lithium–iridium surface phases, revealing additional pathways for chemical modification of borophene. 

Figure 1: (a) Shift of the B 1s core level to higher binding energies and (b) reduction of the sample’s work function arising from the charge transfer from Li to B atoms. (c) Lithium atoms (yellow) deposited on borophene (magenta) induce deformation of borophene’s crystal lattice as a consequence of significant charge redistribution within the system, visualized in (d). Adapted from ACS Nano 20, 20198 (2026). 

Beyond providing new fundamental insights into the chemistry and physics of two-dimensional boron materials, this work establishes an important reference point for future studies aimed at engineering borophene-based systems. The findings contribute to a deeper understanding of how atomic-scale interactions can be used to tailor the electronic properties of emerging materials for applications in nanoelectronics, catalysis, and energy-related technologies.

S. Kamal¹, I. Seo², I. Cojocariu^3,4, M. Jugovac^3,4, A. Locatelli⁴, Y. Gohda⁵, M. Kralj¹, T. O. Menteş^4, M. Petrović^1
1 Centre for Advanced Laser Techniques, Institute of Physics, Zagreb, Croatia
² Graduate School of Natural Science and Technology, Shimane University, Nishi-Kawatsucho, Matsue, Shimane, Japan
³ Physics Department, University of Trieste, Trieste, Italy
⁴ Elettra Sincrotrone Trieste S.C.p.A., Basovizza, Trieste, Italy
⁵ Department of Materials Science and Engineering, Institute of Science Tokyo, Yokohama, Japan

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