2D Materials

Low-temperature STM allows to resolved the atomic and electronic structure of atomically thin two-dimensional (2D) electronic materials such as graphene and the transition metal dichalcogenides (TMDCs) MoS2, WS2, MoSe2, .. etc. Scanning tunnelling spectroscopy (LT-STS) allows to access some of the materials' electronic properties such as local doping and band structure. A topographic image of a graphene monolayer transferred to a sapphire substrate is shown on the right. The inserts show the surface morphology/roughness arising from the substrates, and the characteristic hexagonal carbon lattice, respectively

Topological Materials

LT-STM/STS has direct access to materials' electronic structure both in real-space and in reciprocal space. In particular, this allows to study band structure and quasiparticle scattering in novel topological materials. Quasiparticle interference (QPI) spectroscopy at low temperature for example allows to map out the material's band structure and infer information about topological protection of electronic states. The image on the right shows the cleaved surface of the topological line-nodal Dirac semimetal zirconium silicon sulfide (ZrSiS), including a number of atomic lattice defects. The top inset shows local charge density oscillations around one of these defects which is situated below the ZrSiS surface. 2D-FFT (bottom image) of such data allows reconstruction the material's Fermi surface at constant energy to infer information such as topological protection of electronic states. Read more here

Atomic Manipulations and Lithography

Interactions of the STM's probe tip and the sample's surface allows for atomic manipulations and lithography. Ultimately, this can allow for the construction of atomic-scale electronic devices and device architectures which can be studied, not only by STM but also in electron transport. The image on right shows a few-atom double quantum dot (DQD) device with source (S) and drain (D) leads, lithographically defined by STM lithography on the hydrogen terminated surface of a silicon substrate. Read more here