We have designed a new Scanning Tunneling Microscope (STM) setup with a custom designed state-of-the-art optical access to enable the location of nanoscale structures, as well as the atomic scale imaging and tunneling spectroscopy of graphene and other 2D materials and their nanostructures with the capability of spin-polarized measurements.
We have developed a novel device concept based on zigzag graphene nanoribbons with spin-polarized edges that enables the control of both charge and spin signals using a single back-gate electrode in the simplest three-terminal field effect transistor configuration.
Besides graphene, we also have demonstrated that the atomic level modification of 2D MoS2 crystals through the substitution of single S atoms by oxygen can give rise to novel material properties. We have shown that such a peculiar oxygen substitution reaction can spontaneously occur under ambient conditions, and the resulting oxygen substitution sites act as single atomic catalytic centers substantially improving the catalytic activity of MoS2 single layers for the hydrogen evolution reaction.
We have demonstrated the efficient strain engineering of the bandgap of 2D MoS2 single layers by investigating nanometer scale MoS2 bubbles. We could provide unambiguous evidence for the occurrence of the direct to indirect bandgap transition in MoS2 single layers upon 2% biaxial tensile strain, by measuring a smaller electronic bandgap (tunneling spectroscopy) than the optical gap (photoluminescence).
We have developed a novel Atomic Force Microscope based nanofabrication technique that enables patterning graphene nanostructures on insulating substrates, enabling the AFM based fabrication of graphene nanostructures with lateral size below 10 nm, and high edge quality. This has been achieved by the direct mechanical cutting of graphene by the AFM tip along its high symmetry crystallographic directions.
We have integrated the graphene nanoscale constrictions fabricated by our AFM lithography technique into nanoelectronics devices revealing an unprecedentedly robust quantum point contact operation achieved with graphene, displaying well-defined quantized conductance plateaus down to small quantum numbers, in the absence of a magnetic field, even on standard SiO2/Si substrates , and up to 40K temperatures.
We have synthesized 2D MoSe2 crystals with a high density of Mo vacancies identified by tunneling microscopy and spectroscopy measurements. Theoretical calculations in excellent agreement with the experimental data predict that such defects possess a magnetic moment that can be tuned between 0 and 5 Bohr magnetrons by tuning the Fermi level of the MoSe2 sheet. This way a fully electrical control of the resulting magnetic moment can be achieved.
We have developed a novel nanoengineering technique of graphene, based on inducing nanoscale corrugations of high aspect ratio, allowing the edge-free confinement of its charge carriers. This has enabled the confinement of graphene plasmons into sub-5nm areas, tuning up their resonance frequency into the commercially relevant visible range.
We have provided experimental evidence that the ground state of relatively thick (> 8 layers) ABC graphite samples consists of competing antiferromagnetic and correlated paramagnetic states
