Quantum confinement of Dirac quasiparticles in graphene patterned with subnanometer precision

TL;DR

This paper demonstrates a method using STM to create precisely patterned graphene nanostructures that effectively confine Dirac quasiparticles, enabling tunable electronic properties and opening up possibilities for graphene-based quantum devices.

Contribution

The authors develop a sub-nanometer precision patterning technique on graphene using STM, overcoming previous fabrication challenges and enabling efficient confinement of Dirac quasiparticles.

Findings

Graphene nanostructures confine Dirac quasiparticles effectively.

Energy band gaps up to 0.8 eV are achieved in quantum dots.

Band gap scales inversely with dot size, consistent with Dirac fermion behavior.

Abstract

Quantum confinement of graphene Dirac-like electrons in artificially crafted nanometer structures is a long sought goal that would provide a strategy to selectively tune the electronic properties of graphene, including bandgap opening or quantization of energy levels However, creating confining structures with nanometer precision in shape, size and location, remains as an experimental challenge, both for top-down and bottom-up approaches. Moreover, Klein tunneling, offering an escape route to graphene electrons, limits the efficiency of electrostatic confinement. Here, a scanning tunneling microscope (STM) is used to create graphene nanopatterns, with sub-nanometer precision, by the collective manipulation of a large number of H atoms. Individual graphene nanostructures are built at selected locations, with predetermined orientations and shapes, and with dimensions going all the way from 2 nanometers up to 1 micron. The method permits to erase and rebuild the patterns at will, and it can be implemented on different graphene substrates. STM experiments demonstrate that such graphene nanostructures confine very efficiently graphene Dirac quasiparticles, both in zero and one dimensional structures. In graphene quantum dots, perfectly defined energy band gaps up to 0.8 eV are found, that scale as the inverse of the dots linear dimension, as expected for massless Dirac fermions