The Fuhrer Group’s research focuses on atomically thin materials, also known as two-dimensional (2D) materials. The prototypical atomically thin material is graphene, a single atom-thick plane of carbon, the basic constituent of graphite. Other classes of materials studied in the Fuhrer Group include the atomically thin semiconducting transition metal dichalcogenides (TMDs) such as MoS2 and WS2, topological insulators such as Bi2Se3. and topological Dirac semimetals such as Na3Bi.
Novel Electronic Properties
Many atomically thin materials show novel electronic properties. In graphene, electrons behave as if they have no mass, moving at a constant velocity regardless of their energy (much like photons, particles of light). Topological insulators such as Bi2Se3 are three-dimensional materials whose two-dimensional surfaces are conducting. The conducting 2D surface shares the massless property of electrons with graphene, and a new property that the quantum mechanical “spin” of the electrons is coupled to the direction of their momentum, creating new interplays between charge and spin polarizations and currents. The layered transition metal dichalcogenides include new 2D semiconductors such as MoS2 and WS2, in which the electrons have a “valley” degree of freedom which is coupled to spin, and can be controlled electrically and optically.
All the 2D materials share in common that their interesting electronic states lie at the surface of the material, and are therefore sensitive to the condition of that surface. Control of the surface through ultra-high vacuum surface science techniques leads to new ways to control the properties of the materials, for instance changing the dielectric environment (by deposition of dielectric material), charge (by deposition of ionized impurities), point defects (thorugh removal of atoms by sputtering), magneitsm and spin orbit coupling (through heavy-metal adatoms), etc.
The Fuhrer Group has developed unique techniques to study the electronic transport properties of 2D materials in situ in ultra-high vacuum, at cryogenic temperature. At Monash, the Fuhrer Group is combining these techniques with atomic-resolution scanning probe microscopy in order to image the atomic structure of modified surfaces and simultaneously measure the electronic transport properties of the material.
The Fuhrer Group makes use of the Australian Synchrotron to do x-ray photoelectron spectroscopy (XPS) in support of the themes of investigation outlined above.
The Fuhrer Group’s research has led to new concepts for infrared and THz detection using graphene devices (see here and here), and new conducting transparent electrodes based on lithium-intercalated few-layer graphene.