Germanene is a material made up of a single layer of

germanium Germanium is a chemical element; it has Symbol (chemistry), symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid or a nonmetal in the carbon group that is chemically ...

atoms. The material is created in a process similar to that of silicene and

graphene Graphene () is a carbon allotrope consisting of a Single-layer materials, single layer of atoms arranged in a hexagonal lattice, honeycomb planar nanostructure. The name "graphene" is derived from "graphite" and the suffix -ene, indicating ...

, in which high vacuum and high temperature are used to deposit a layer of germanium atoms on a substrate. High-quality thin films of germanene have revealed unusual two-dimensional structures with novel electronic properties suitable for semiconductor device applications and materials science research.

Preparation and structure

In September 2014, G. Le Lay and others reported the deposition of a single atom thickness, ordered and two-dimensional multi-phase film by

molecular beam epitaxy Molecular-beam epitaxy (MBE) is an epitaxy method for thin-film deposition of single crystals. MBE is widely used in the manufacture of semiconductor devices, including transistors. MBE is used to make diodes and MOSFETs (MOS field-effect transis ...

upon a

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

surface in a

crystal lattice In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystal, crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that ...

with

Miller indices Miller indices form a notation system in crystallography for lattice planes in crystal (Bravais) lattices. In particular, a family of lattice planes of a given (direct) Bravais lattice is determined by three integers ''h'', ''k'', and ''� ...

(111). The structure was confirmed with

scanning tunneling microscopy A scanning tunneling microscope (STM) is a type of scanning probe 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 ...

(STM) revealing a nearly flat honeycomb structure. Additional confirmation was obtained by spectroscopic measurement and

density functional theory Density functional theory (DFT) is a computational quantum mechanical modelling method used in physics, chemistry and materials science to investigate the electronic structure (or nuclear structure) (principally the ground state) of many-body ...

calculations. The development of high quality and nearly flat single atom films created speculation that germanene may replace

if not merely add an alternative to the novel properties of related nanomaterials. Bampoulis and others have reported the formation of germanene on the outermost layer of Ge₂Pt nanocrystals. Atomically resolved STM images of germanene on Ge₂Pt nanocrystals reveal a buckled honeycomb structure. This honeycomb lattice is composed of two hexagonal sublattices displaced by 0.2 Å in the vertical direction with respect to each other. The nearest-neighbor distance was found to be 2.5±0.1 Å, in close agreement with the Ge-Ge distance in germanene. Based on STM observations and density functional theory calculations, formation of an apparently more distorted form of germanene has been reported on

platinum Platinum is a chemical element; it has Symbol (chemistry), symbol Pt and atomic number 78. It is a density, dense, malleable, ductility, ductile, highly unreactive, precious metal, precious, silverish-white transition metal. Its name origina ...

. Epitaxial growth of germanene crystals on

GaAs Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a zinc blende crystal structure. Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated circui ...

(0001) has also been demonstrated, and calculations suggest that the minimal interactions should allow germanene to be readily removed from this substrate. Germanene's structure is described as "a group-IV graphene-like two-dimensional buckled nanosheet". Adsorption of additional germanium onto the graphene-like sheet leads to formation of "

dumbbell The dumbbell, a type of free weight, is a piece of equipment used in weight training. It is usually used individually and/or in pairs, with one in each hand. History The forerunner of the dumbbell, halteres, were used in ancient Greece as li ...

" units, each with two out-of-plane atoms of germanium, one on either side of the plane. Dumbbells attract each other. Periodically repeating arrangements of dumbbell structures may lead to additional stable phases of germanene, with altered electronic and magnetic properties. In October 2018, Junji Yuhara and others reported that germanene is easily prepared by a segregation method, using a bare Ag thin film on a Ge substrate and achieved in situ its epitaxial growth. The growth of germanene, akin to graphene and silicene, by a segregation method, is considered to be technically very important for the easy synthesis and transfer of this highly promising 2D electronic material.

Properties

Germanene's electronic and optical properties have been determined from ''

ab initio ( ) is a Latin term meaning "from the beginning" and is derived from the Latin ("from") + , ablative singular of ("beginning"). Etymology , from Latin, literally "from the beginning", from ablative case of "entrance", "beginning", related t ...

'' calculations, and structural and electronic properties from first principles. These properties make the material suitable for use in the channel of a high-performance

field-effect transistor The field-effect transistor (FET) is a type of transistor that uses an electric field to control the current through a semiconductor. It comes in two types: junction FET (JFET) and metal-oxide-semiconductor FET (MOSFET). FETs have three termi ...

and have generated discussion regarding the use of elemental monolayers in other electronic devices. The electronic properties of germanene are unusual, and provide a rare opportunity to test the properties of

Dirac fermion In physics, a Dirac fermion is a spin-½ particle (a fermion) which is different from its antiparticle. A vast majority of fermions fall under this category. Description In particle physics, all fermions in the standard model have distinct antipar ...

s. Germanene has no

band gap In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to t ...

, but attaching a hydrogen atom to each germanium atom creates one. These unusual properties are generally shared by

, silicene, germanene, stanene, and plumbene.

References

External links

Meet Graphene's Sexy New Cousin Germanene
* ttp://www.newsledge.com/graphene-exciting-germanene-makes-appearance-9428 Graphene Family Tree? Germanene Makes Its Appearance* *{{Cite journal, title = Low-energy effective Hamiltonian involving spin-orbit coupling in silicene and two-dimensional germanium and tin, journal = Physical Review B, date = 1 January 2011, volume = 84, issue = 19, pages = 195430, doi = 10.1103/PhysRevB.84.195430, first = Cheng-Cheng, last = Liu, bibcode = 2011PhRvB..84s5430L, arxiv = 1108.2933, s2cid = 44216872
CNRS Website (2015)CNRS Website (2017)
Germanium Allotropes Group IV semiconductors Two-dimensional nanomaterials 2014 in science Substances discovered in the 2010s