Two-dimensional silica (2D silica) is a layered

polymorph Polymorphism, polymorphic, polymorph, polymorphous, or polymorphy may refer to: Computing * Polymorphism (computer science), the ability in programming to present the same programming interface for differing underlying forms * Ad hoc polymorphi ...

silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

. Two varieties of 2D silica, both of hexagonal crystal symmetry, have been grown so far on various metal substrates. One is based on SiO₄ tetrahedra, which are

covalently A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atom ...

bonded to the substrate. The second comprises

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

-like fully saturated sheets, which interact with the substrate via weak van der Waals bonds. One sheet of the second 2D silica variety is also called hexagonal bilayer silica (HBS); it can have either ordered or disordered (amorphous) structure. 2D silica has potential applications in electronics as the thinnest gate dielectric. It can also be used for isolation of graphene sheets from the substrate. 2D silica is a wide band gap semiconductor, whose band gap and geometry can be engineered by external electric field. It was shown to be a member of the auxetics materials family with a negative Poisson's ratio.

References

Two-dimensional nanomaterials Silicon dioxide Silica polymorphs {{nano-tech-stub