In BioGraphING, the researcher realized the first mechanically controlled break junctions (MCBJs) based on graphene electrodes to study the charge transport across the nanoscopic junctions.
The major advances that were made throughout the MC project are:
• Mechanical and electrical robustness and stability of the device compared to its bulk metal counterpart (i.e. Au break junctions used in the host group).
• Reliability and reproducibility of the fabrication using standard cleanroom processing.
• Statistical significance of the results (> 10,000 cycles at room temperature in air).
• Sub-nanometer tuning of the electrode spacing using a simple mechanical tuning knob to control the inter-electrode distance.
Furthermore, the new platform allowed the discovery of new fundamental quantum physical process, including quantum interference phenomena, that had only been reported from a theoretical standpoint but not achieved in practice:
• Observation of rare room temperature quantum interference effects during sliding of two graphene sheets across each other
• Low temperature (4 K) measurements of mechanically-tunable Coulomb blockade in a single graphene quantum dot inside the junction
The first paper published during the project (Nature Nanotechnology, 13, 1126–1131(2018)) demonstrates the first room-temperature, periodic conductance oscillations as a function of atomic-scale displacements in quantum coherent graphene nanoconstrictions. Our approach, based on monitoring the electrical conductance of graphene during uniaxial deformation, is entirely novel and overcomes a longstanding challenge for controllably tuning quantum interference effects in graphene by using a mechanical tuning knob with subnanometer resolution.
Given that the graphene MCBJ device demonstrates excellent electronic and mechanical properties, as well as a host of intriguing fundamental physical effects, the focus of the project shifted towards understanding the origin of the latter phenomena.
During the MC fellowship, massively parallel fabrication of crack-defined gold break junctions featuring sub-3 nm gaps was demonstrated, in a collaborative project with KTH University. The current-voltage characteristics were studied in detail and proved that single molecules can be individually trapped and measured at room temperature and at liquid nitrogen temperature. The results were published in Nature Communications (2018).
During the two-year period, the researcher disseminated the results of the project at the following international conferences as contributed speaker:
- From Solid state to Biophysics- From Basic to Life Sciences, Cavtat, Croatia, 2018
- Graphene Week 2018 - San Sebastian, Spain, 2018
- International Conference on Materials for Advanced Technologies - Singapore, 2019
- NT19: International Conference on the Science and Application of Nanotubes and Low-Dimensional Materials - Würzburg, Germany, 2019
The researcher was also an invited speaker at the 1st Kavli NanoLab Cleanroom User Meeting 2018.
