Natural Graphene vs. Artificial Graphene
The fixed hexagonal structure of graphene exhibits a fixed atomic arrangement. Within this structure exists the Diract point, which occurs as a result of the energy to movement relation in graphene existing in a linear fashion near the six individual corners of the hexagonal structure. As a result of the zero density that exists at each Dirac point, electric conductivity is typically low, however, doping of graphene to adjust the Fermi level can enhance the electronic conductivity of this material that allows it to be so well known for today.
While this structure has been a highly desirable platform for various electronic applications, it can also limit its versatility, as researchers must often adapt other aspects of their experiments to ensure that graphene will work successfully. As a new and expanding field of research, the development of an artificial graphene (AG) material has already successfully been engineered according to varying spacing and configuration requirements. Natural graphene material is also extremely limited in its ability to produced on a large-scale, therefore the creation of an AG material would also allow researchers to have more control over the manufacturing process and develop ways in which this material can be mass-produced.
The Artificial Graphene Design
To create the AG lattices, the researchers utilized nanolithography and etching tools to pattern gallium arsenide, a standard semiconductor material. Once this was completed and hexagonal patterning confined the electrons in a lateral direction, the researchers then superimposed the fabricated AG lattices to create two-dimensional (2D) sheet.
The evaluation of the electronic states of the fabricated material was performed by resonant inelastic light scattering (RILS), a technique that scatters high-energy x-ray photons onto a material to evaluate its electronic structure at the molecular level. RILS data showed that as electron energy transitioned from one state to another, they loss a significant amount of energy that approached zero in a linear fashion. This specific pattern of electrical energy, also known as the Dirac point, has also been found in natural graphene and accounts for some of its magnificent conductive properties. To fully elucidate the Dirac Point property found within the AG structure, the researchers measured inter-AG-band transitions by tuning the depth of etching during their original fabrication methods. These band transitions are found when the Fermi level is situated below the energy at both the K and K’ points.
By discovering the Dirac point in their artificial graphene material, the researchers are able to design variations into the honeycomb structure to accommodate a wide realm of semiconductor applications that are particularly advantageous for device stability and integration. Additionally, the discoveries made in this study allow for a growth in the research areas of fractal quantum physics, understanding mechanisms of controlling spin-orbit coupling and simulating the opening of an energy gap by breaking inversion symmetry. Researchers are also hopeful that the tunneling effects of MDFs confirmed in this paper will further research efforts in this direction, thereby allowing for the creation of defects to allow quantum dots to fit within the lattice of graphene and similar materials.
The prospect of creating an artificial graphene material could be advantageous to a number of industries that have looked at this material to enhance their current and future electronic products. Improving the ease of production of a superconductive material that exhibits every unique property of graphene could show a promising future for industrial applications, as current production techniques of graphene lack the technical ability to adapt to larger scale requirements.
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- “Observation of Dirac bands in artificial graphene in small-period nanopatterned GaAs quantum wells” S. Weng, D. Scarabelli, et al. Nature. (2017). DOI: 10.1038/s41565-017-0006-x.