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Early Stage Researcher 10, CTH, SWEDEN


Project title and work package:

Quantum transport in graphene edges and grain boundaries, work packages 2D-materials growth and nanostructuring and Electron transport in reduced dimensionality.



Performance of graphene-based electronic devices is limited by defects including edges and grain boundaries. Your project aims at clarification and characterisation of the effect of these defects in graphene-based devices, both in epitaxial and CVD graphene. Grain boundaries in the CVD-grown graphene from GRA SEMI will be located and marked using TEM, and electronic devices containing grain boundaries will be fabricated. Charge transport will be studied in these devices, in particular in the quantum Hall regime, where the grain boundary may serve as a metallic short between the edge states, preventing complete vanishing of the longitudinal resistance and exact resistance quantisation.

In collaboration with Early Stage Researcher 15 (GRA SEMI, Spain), you will produce Graphene nanoribbons by annealing a silicon carbide substrate in an argon atmosphere at temperatures of 2000 °C. The obtained few nanometre high steps serve as a seed for graphene growth. During the growth, the edges of the nanoribbons are self-organised. Your objective is to study the effect of this self-organisation on charge transport and explore new possibilities for the charge- and spin-based electronics opened in these self-organised nanostructures. The nanoribbons contacted by standard EBL will be measured in magneto-transport at various temperatures in order to determine the mean free path and phase coherence length of the charge carriers.

The edge disorder often governs electronic properties, leading to Coulomb blockade and masking quantum confinement. By looking at the Coulomb blockade effects, you will evaluate and characterise the degree of the edge irregularity achievable and aim at the observation of quantum confinement effects in the ribbons. Local spectroscopy experiments will be pursued using a cryogenic STM at CNRS, France in collaboration with Early Stage Researcher 2.


Expected Results:

- Charge transport in graphene nanodevices measured.

- Growth conditions of self-organised graphene nanoribbons clarified & their electronic properties evaluated experimentally.

- The edge quality of self-organised graphene nanoribbons on SiC steps evaluated by cryogenic AFM-STM.



Planned secondments:

at GRA SEMI, Spain (2 months, Year 1) to get samples of CVD graphene and locate grain boundaries using TEM. At CNRS, France (1 month, Year 2) to determine the structure of the nanoribbons edges and achieve scanning tunnelling spectroscopy on them. At RAITH, Germany (1 month, Year 2) for training on resistless nanofabrication based on focussed ion or EBID.



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