Colloquium – Surface-sensitive studies of electronic properties in 2D materials

Two-dimensional (2D) materials provide a unique platform in which structural,
electronic, and functional properties are governed almost entirely by surface and interfacial
effects. Thus, understanding and controlling these properties is essential for their integration into
future electronic and energy-efficient technologies. In this presentation, representative results
are obtained by using advanced surface-sensitive experimental approaches that enable the
investigation of 2D materials, such as graphene, germanene, and transition metal
chalcogenides, at the atomic scale. Scanning Tunneling Microscopy (STM) is employed to
probe and locally manipulate structural and electronic properties with atomic precision, while
complementary synchrotron-based techniques offer element-specific and surface-resolved
access to electronic structure, chemical states, and interfacial phenomena. The results
demonstrate how lattice registry, Moiré superstructures, interfacial coupling, and local structural
distortions strongly influence the electronic landscape of 2D systems, leading to spatial
modulations of charge density, work function, and local density of states. Local nano-contacts
created by STM further reveal how mechanical deformation and layer decoupling can be used
to tune charge injection and junction behavior at the nanoscale. By combining photoemission
spectroscopy, polarization-dependent x-ray absorption, electron diffraction, and first-principles
calculations, our studies separate the roles of structural asymmetry and electronic orbital
character in driving anisotropic electronic responses and how intrinsic properties can be
controlled. Overall, these findings highlight the critical role of surfaces, interfaces, and local
structural effects in shaping the electronic behavior of 2D materials, offering new pathways for
their controlled manipulation in future nanoscale and quantum technologies.