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Germanene is a material made up of a single layer of germanium atoms. The material is created in a process similar to that of silicene and graphene, 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.
Additional confirmation was obtained by spectroscopic measurement and density functional theory calculations. The development of high quality and nearly flat single atom films created speculation that germanene may replace graphene 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. Epitaxial growth of germanene crystals on Gallium arsenide(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" 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.
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