Artificial lattice is a term encompassing every atomic-scale structures designed and controlled to confine electrons onto a chosen lattice. Research has been done on multiple geometries and one of the most notable being what is called molecular graphene (in order to mimic

graphene Graphene () is an allotrope of carbon consisting of a Single-layer materials, single layer of atoms arranged in a hexagonal lattice nanostructure.

structure). Molecular graphene is a part of two-dimensional artificial lattices. Artificial lattices can be studied to test theoretical topology predictions or for their engineered electronic proprieties. Those materials should still be considered at a research stage.

Synthesis

Synthesis of such materials is often achieved using

Atomic manipulation Atomic manipulation is the process of moving single atoms on a substrate using Scanning Tunneling Microscope (STM). The atomic manipulation is a surface science technique usually used to create artificial objects on the substrate made out of atoms ...

scanning tunneling microscope A scanning tunneling microscope (STM) is a type of microscope used for imaging surfaces at the atomic level. Its development in 1981 earned its inventors, Gerd Binnig and Heinrich Rohrer, then at IBM Zürich, the Nobel Prize in Physics in 1986 ...

atomic force microscope Atomic force microscopy (AFM) or scanning force microscopy (SFM) is a very-high-resolution type of scanning probe microscopy (SPM), with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the opt ...

. More and more efforts are being made to achieve a similar atomic precision with focused electron beams. Those methods aren't adapted for a mass production of nanostructures as each molecule has to be moved one by one. To solve this issue, new methods of synthesize those compounds are being researched such as chemical bottom-up synthesis. Currently, multiple methods, often complementary, exist for synthesizing such materials : * Patterning of electron gas extension : this is the method used when the lattice is built from adsorbates over Cu(111) surfaces. * Using localized orbitals from the atomic sites. In the case of molecular graphene,

carbon monoxide Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

molecules on Cu(111) surface can be used. Other materials have been shown to be suitable for making molecular graphene suchlike

Coronene Coronene (also known as superbenzene and cyclobenzene) is a polycyclic aromatic hydrocarbon (PAH) comprising seven peri-fused benzene rings. Its chemical formula is . It is a yellow material that dissolves in common solvents including benzene, tol ...

. Substrates such as Cu(111) are interesting because they have a 2D free-electron-like surface state. If CO molecules are placed onto appropriate positions, as the Cu(111) surface state is scattered from the CO molecules, the surface state electron gas can be confined onto different geometries (e.g. a honeycomb).

Proprieties

The main interest of artificial lattice is that its lattice proprieties (such as the lattice spacing) can be precisely controlled. In the case of molecular graphene, similarities in structure with graphene can provide an indirect to study graphene proprieties. Using a triaxial strain, it is possible to study how graphene react to intense magnetic fields. This strain (creating what is called a pseudo magnetic field) will alter the electronic structure of the molecule in the same fashion a magnetic field would. With this method, we can study how graphene would react to field up to 60 T. Some artificial lattices, such as molecular graphene, also exhibits semi-conductors' behaviors. PNP junctions can be made with the juxtaposition of two artificial graphene lattices with different lattice spacing. Indeed,

Fermi level The Fermi level of a solid-state body is the thermodynamic work required to add one electron to the body. It is a thermodynamic quantity usually denoted by ''µ'' or ''E''F for brevity. The Fermi level does not include the work required to remov ...

of a molecular graphene is directly linked to its lattice spacing. Graphen

Multiple geometries for artificial lattices has been researched and created. Some of those geometries are : * Graphene * Lieb lattices *

Sierpiński triangle The Sierpiński triangle (sometimes spelled ''Sierpinski''), also called the Sierpiński gasket or Sierpiński sieve, is a fractal attractive fixed set with the overall shape of an equilateral triangle, subdivided recursively into smaller equi ...

Penrose tiling A Penrose tiling is an example of an aperiodic tiling. Here, a ''tiling'' is a covering of the plane by non-overlapping polygons or other shapes, and ''aperiodic'' means that shifting any tiling with these shapes by any finite distance, without ...

* Kagome lattice * Kekulé lattice Some of those geometries have a non-integer

Hausdorff dimension In mathematics, Hausdorff dimension is a measure of ''roughness'', or more specifically, fractal dimension, that was first introduced in 1918 by mathematician Felix Hausdorff. For instance, the Hausdorff dimension of a single point is zero, o ...

as they are fractals. Those dimensions can be approximated using box counting methods. This dimension will dictate how electrons of the artificial lattice will behave and move in space.

Notes

:1. Bottom-up synthesis are chemical processes used in nanotechnologies to create nanoparticles. The principle is to start from atoms, then to gather them in clusters of atoms which will be finally merged into nanoparticles. :2. Triaxial strain is obtained in molecular graphene with a modification of the arrangement of molecules.

References

{{Reflist * Condensed matter physics

Synthesis

Proprieties

See also

Notes

References