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Atomic structure characteristics of graphene

wallpapers News 2021-08-12
Graphene is a crystalline allotrope of carbon with two-dimensional properties. Its carbon atoms are densely arranged into regular atomic-scale barbed wire (hexagons).
Each atom has four bonds, a σ bond has one of its three neighboring atoms, and a π bond lies outside the plane. The distance between atoms is about 1.42Å.
Structure and nature relationship
The hexagonal lattice of graphene can be seen as two interlaced triangular lattices. This idea was successfully used to calculate the band structure of a single graphite layer.
The stability of graphene is due to its close-packed carbon atoms and sp2 orbital hybridization-s orbitals, px and py form σ bonds. The last pz electron forms a π bond. The π bonds hybridize together to form π bands and π∗ bands. These bands are responsible for most of the remarkable electronic properties of graphene, as they allow the free movement of electrons in half-filled bands.
Graphene sheets in the solid form usually show evidence of diffraction of graphite stacking in the (002) direction. The same is true for some single-walled nanostructures. However, unexfoliated graphene with only (hk0) rings was found in the core of the graphite onion before the sun. Transmission electron microscopies studies show that there are defects on the flat graphene sheet and suggest the role of two-dimensional crystallization of the melt. When graphene is exposed to carbon-containing molecules (such as hydrocarbons), it can self-repair holes in the sheet. Bombarded by pure carbon atoms, the atoms are perfectly arranged into a hexagon, filling the hole.
The atomic structure of single-layer graphene was studied by transmission electron microscopy (TEM). The electron diffraction pattern shows the expected honeycomb lattice. The suspended graphene also showed flat "ripples" with amplitude of about 1 nanometer. Due to the instability of two-dimensional crystals, these ripples may be inherent to the material or may originate from the ubiquitous dirt seen in all graphene TEM images. The atomic resolution real space image of isolated single-layer graphene can be obtained by scanning a tunneling microscope on a SiO2 substrate. Photoresist residue (which must be removed to obtain an atomic resolution image), maybe the "adsorbed matter" observed in the transmission electron microscope image and may explain the observed wrinkles. The wrinkles on the SiO2 are caused by the conformation of the graphene and the underlying SiO2 and are not inherent.


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