In this paper, a perspective on the application of Spatially- and Angle-Resolved PhotoEmission Spectroscopy (ARPES) for the study of two-dimensional (2D) materials is presented. ARPES allows the direct measurement of the electronic band structure of materials generating extremely useful insights into their electronic properties. The possibility to apply this technique to 2D materials is of paramount importance because these ultrathin layers are considered fundamental for future electronic, photonic and spintronic devices. In this review an overview of the technical aspects of spatially localized ARPES is given along with a description of the most advanced setups for laboratory and synchrotron-based equipment. This technique is sensitive to the lateral dimensions of the sample. Therefore, a discussion on the preparation methods of 2D material is presented. Some of the most interesting results obtained by ARPES are reported in three sections including: graphene, transition metal dichalcogenides (TMDCs) and 2D heterostructures. Graphene has played a key role in ARPES studies because it inspired the use of this technique with other 2D materials. TMDCs are presented for their peculiar transport, optical and spin properties. Finally, the section featuring heterostructures highlights a future direction for research into 2D material structures.

We have performed ab initio calculations to investigate the adsorption of Li onto the clean and oxygenated diamond C(100) surface. Despite a large amount of interest in alkali-metal absorption on clean and oxidized semiconductor surfaces for both fundamental and technological applications, lithium adsorption on the diamond surface has not been reported. We find that Li adopts structures on the clean C(100) surface similar to those reported for Na, K, and Rb on diamond, though Li exhibits significantly higher binding energies in the range 2.7\char21{}3.1 eV per Li adsorbate. For the oxygenated C(100)-(1\ifmmode\times\else\texttimes\fi{}1):O surface, the lowest energy involving a full Li monolayer structure shows an exceptionally large work-function shift of $-${}4.52$\hskip0.3em${}eV relative to the clean surface, an effect similar to that seen for CsO on diamond, but with a higher binding energy of 4.7 eV per Li atom. We propose that such a system, if verified by experiment, is suitable for the surface coating of diamond-based vacuum electronic devices, as it should exhibit higher thermal stability than the commonly used CsO surface while retaining the advantage of a large lowering of the work function.