Ever since the initial synthesis of graphene kicked off the search, people have been aware of the potential advantages of finding new 2-D materials. Graphene is a layer of carbon atoms, bound together in a simple hexagonal structure. Carbon was already well-known for forming a fascinating array of chemical bonds; allotropes and fullerenes including C-60 – ‘Bucky-balls’ – having already been synthesised. But it was soon realised that 2-D allotropes of other elements could be formed, like silicene and stanene for silicon and tin respectively. The different properties of these atoms resulted in differing properties for their 2-D analogues.
Germanium was first discovered in 1886: although originally it didn’t see many applications industrially, as it was considered to be a poor electrical conductor, by the 1940s and 1950s, its useful optical and electronic properties as a semiconductor were recognised. Early transistors were often made of germanium – and many still are, although once it became easier to synthesise silicon with the appropriate levels of purity, the allure of germanium fell.
In 2014, a decade after graphene was first isolated at the University of Manchester, two different research teams were able to create germanene. This material is essentially the cousin of graphene; it consists of a single layer of germanium atoms in the characteristic hexagonal structure associated with 2-D materials. Graphene had originally been studied on metal plates in the 1960s before it was rediscovered, isolated, and characterised in 2004; this germanene was created by a European team through molecular beam epitaxy onto a gold substrate, while a Chinese team used platinum. In this process, individual atoms are deposited onto the substrate at very low pressures and high temperatures.
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SOURCE: AZO Materials