María C. Asensio
Institute of Materials Science of Madrid (ICMM), CSIC, Cantoblanco, 28049 Madrid, Spain
MATINÉE: CSIC Associated Unit between ICMM and the Materials Science Institute (ICMUV), Valencia University, Valencia, Spain

We have witnessed exponential advances in new nanotechnologies based on low-dimensional materials in recent decades. These nanomaterials had shown remarkable properties; however, they would have remained unexploited if, at the same time, we had not developed new tools capable of viewing and scrutinizing objects on a wide range of scales, from a few microns to a few tens of nanometers. Recently, significant progress has been made due to the rapid expansion in the range of modern microscopies, which have successfully achieved nanometer spatial resolution. Nevertheless, the challenge remains to provide powerful high-energy-resolution spectroscopic tools at the nanoscale. To accomplish this goal, the electronic structure must be measured not only regarding the detection of core levels. The electronic structure of delocalized valence bands must also be recorded because these electronic states are directly responsible for chemical bonds, electrical transport, and thermal and mechanical properties.

Traditionally, angle-resolved photoemission spectroscopy (ARPES) is the only technique capable of making sufficiently precise measurements of the dispersion of the band structure of materials in the reciprocal space. We have developed an electronic nano-scope based on the ARPES principles, which can perform spatially resolved ARPES experiments on the nanometer scale. In this presentation, we will review several results of our group using the Nano-ARPES [1] technique. This sophisticated instrument can have a high spatial resolution in several tens of nanometers of real space. That allows the direct imaging of core levels and their chemical shifts, band electronic structures in reciprocal space. Low-dimensional materials of a few atomic layers have been investigated in silicene, graphene multilayers with different stacking, Moiré structures, topological surfaces, and many others [2].

References:
[1] Nano-ARPES, Wikipedia
[2] Z. Gao, et al., Large-area epitaxial growth of curvature-stabilized ABC trilayer graphene, Nat Commun 11, 546 (2020)