Scientists have proposed a new method for the synthesis of two-dimensional polymers based on istriangular. It turned out that the new material is similar to graphene, the structure of the kagome and the same Dirac cones — unusual energy dependence of the electronic States of the output. However, unlike graphene, two-dimensional polymer has semiconductor properties. The material will find application in nanoelectronic devices. Article published in the journal Nature Materials.
Similar to some graphene materials one can observe an interesting feature of the Dirac cones. This feature of the electronic structure is named for the kind of dependence of the energy States of electrons on their momentum. If we plot this dependence for graphene can be observed, as the valence zone and conduction diverge from the Fermi level in the form of conical surfaces. For most materials on this chart instead of cones, you notice duopolistic hyperboloid. This seemingly minor change based on influences of material properties and can generate, for example, anomalous Hall effect, surface superconductivity and even superfluidity.
Previously, scientists predicted the existence of Dirac cones in a promising class of materials two-dimensional — 2D-π-conjugated polymers (2DCP). However, due to the small size of the domains 2DCP and a large number of defects to observed these features experimentally so far failed. Previously, the synthesis of these two-dimensional polymers, the researchers conducted on the surface of the liquid, but obtained by this method materials lacked long-range order in the arrangement of atoms and the size of the domains does not exceed 20× 20 nanometers.
Physics under the guidance of Giorgio Contini (Contini Giorgio) from the University of Rome tor Vergata came to obtaining two-dimensional conjugated polymers on the other hand. They took as the basis of the reaction of Ullmann. During her two aromatic compounds containing halogen atoms, are combined into one structure under the action of a catalyst. As raw material, the researchers used two similar compounds — tribromoimidazole (TBTANG) and tribromoresorcinol (TBTANGO). The molecules of these substances have a triangular shape with the nitrogen atom in the center and three aromatic rings on the sides. Have TBTANG rings connected by oxygen atoms, and TBTANGO — carbon atoms associated with oxygen. Before the synthesis of scientists have predicted using the density functional method that two-dimensional materials of these molecules are semiconductors with a band gap of respectively 1.8 and 2.4 electron volts.