Researchers from the Ohio State University (Columbus) have developed a new method for stacking germanium on monoatomic layers with ten times better efficiency compared to silicon, while creating a simpler alternative for the production of next-generation materials, such as graphene.
![Monolayers of Germanan crystals with hydrogen atoms at their ends (right) were synthesized by dissolving the calcium salt of the material germanium (left) in hydrochloric acid. [Source: Ohio University].](https://www.hayadan.org.il/images/content3/2013/04/graphene-vs-gramanan.jpg "Monolayers of Germanan crystals with hydrogen atoms at their ends (right) were synthesized by dissolving the calcium salt of the material germanium (left) in hydrochloric acid. [Source: Ohio University].")
We were able to produce an equivalent of graphene from the material germanium - monolayers at the ends of which there are hydrogen atoms, just like the material graphene, only our method is much simpler," said Professor Joshua Goldberger from Ohio State University (Columbus). "In the process, we were also able to transform the material to include a direct bandgap, which allows it to be suitable for optical applications."
The researcher Goldberger claims that he is the first to have succeeded in synthesizing clean crystalline lattices on a millimeter scale of germanium at the ends of which hydrogen atoms (GeH) are found from the discharge of its sodium salt (CaGe2), to obtain a product corresponding to the graphene material at the ends of which hydrogen atoms (CH) are present. The researcher adds and explains that the new material named "germanane" is equivalent to the single-layer version of graphene, a configuration known as "graphane".
Beyond the fact that the new material is based on germanium atoms instead of carbon atoms, as in the case of graphene, the biggest difference between the two materials is that the germanane will be easier to prepare using production equipment prevalent in the semiconductor industry than graphene.
The researchers predict that the new material will be useful in the production of advanced optoelectronic devices and sensors of the next generation, and this is in light of the fact that calculations predict that the electron mobility within it will be five times better than germanium itself (and ten times higher than in silicon) and that the material will have a band gap of 1.53 electron volts (slightly higher than gallium-arsenide material).
Researchers in the field of graphene have already demonstrated that the electronic properties of monolayers composed of semiconductors are better than those of the original material, a finding that has led to numerous scientific efforts to prepare monolayers from additional crystalline structures. The higher ability to transfer the electric charge is achieved by the very flat topology, but by linking different ligands (chemical groups) to these monolayers it will be possible to use these very thin materials also for more sensitive applications, such as advanced, efficient and faster sensing.
Germanium was the first material used to make transistors back in 1947 when Bell Laboratories invented them. Since that discovery, silicon has become the material of choice in the semiconductor industry, although germanium has enjoyed a resurgence in recent years in a variety of applications, starting with fast-response digital transmitters and ending with analog optical detectors.
Other researchers also tried to produce germanium in the configuration of thin monolayers with a thickness of one atom, but they encountered the same problems that arose in the production of graphene monolayers - that is, the inability to obtain perfect crystal lattices across the entire surface of the substrate. In order to solve this problem, the researcher Goldberg inserted calcium atoms between the separate monolayers of the Germanan, thereby enabling their production on a large scale. In the next step, he moved the calcium atoms out and "closed" the holes that were created in the crystal as a result by introducing hydrogen atoms, and this to prevent the material from oxidizing. Thanks to this process, the researchers were able to "peel" the Germanan monolayers and use them to conduct experiments.
In the next step, the researchers intend to produce tangible devices composed of the new material as well as conduct experiments with other molecules that will be inserted at the ends of the layers and that will be used as insulating materials while characterizing their electronic and optical properties. At the current stage, the material is stable up to a temperature of 75 degrees Celsius, and the researchers also hope to improve this value so that the new material can be used in a variety of applications.
