09. September 2021

Nano-balls and diamond chips made of silicon and germanium Nano-balls and diamond chips made of silicon and germanium

Chemists at Goethe University Frankfurt have developed two new classes of materials in the field of nanomaterials and investigated them together with their cooperation partners at the University of Bonn: For the first time, they have succeeded in producing a nano-ball from silicon atoms and a building block for a diamond-like crystal of the semiconductor elements silicon and germanium. The two new classes of materials have application potential, for example, in the miniaturization of computer chips, in high-resolution screens for smartphones, or in solar cells and light-emitting diodes with maximum efficiency. 

The silicon sphere,
The silicon sphere, - synthesized for the first time by chemists at Goethe University Frankfurt and promising new applications in semiconductor technology. Blue: silicon, green: chloride ion, gray: hydrogen. © Graphic: Goethe University Frankfurt
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The latest generations of computer chips are only a few nanometers in size and are becoming increasingly energy-saving and powerful as a result of ongoing miniaturization. Since the etching processes traditionally used in chip production are increasingly reaching their limits, the development of new, nanostructured semiconductor materials is essential. Such nano-semiconductors also play a central role in the conversion of electricity into light and vice versa.

A team at Goethe University Frankfurt led by Matthias Wagner has now succeeded in synthesizing molecular nanoballs of 20 silicon atoms, so-called silafulleranes. The second new class of materials are crystal building blocks made of ten silicon and germanium atoms that have a diamond-like structure. Decisive insights into the electronic structures of the new compounds were provided by computer-aided theoretical analyses from the Bonn research group of Stefan Grimme. The professor of theoretical chemistry is a member of the Transdisciplinary Research Area "Building Blocks of Matter and Fundamental Interactions" at the University of Bonn.

The 20 silicon atoms of silafullerane form a body composed of regular pentagons, a dodecahedron. It encloses a chloride ion. At each silicon corner of the body, a hydrogen atom protrudes outward. Doctoral student Marcel Bamberg, who synthesized the molecule, explains: "Our silafullerane is the long-sought progenitor of this new class of substances. That's because you can easily replace the hydrogen atoms with functional groups, giving the silafullerane different properties." Bonn quantum chemist Markus Bursch adds, "We support this targeted generation of potentially useful properties with theoretical predictions of the resulting effects."

Carbon, which is chemically very similar to the elements silicon and germanium, occurs in comparable forms to the two new classes of materials: Hollow spheres of carbon atoms ("fullerenes") correspond to silafulleranes, and diamonds composed of carbon are composed of adamantane subunits. Fullerenes, for example, increase the efficiency of organic solar cells, could make electric car batteries safer, and promise advances in high-temperature superconductivity. Nanodiamonds also have a wide variety of applications, ranging from pharmaceuticals to catalysis research. Against this background, the researchers in Frankfurt and Bonn are eager to see in which fields their silafulleranes and silicon-germanium adamantanes will prevail.

Publication: Marcel Bamberg, Markus Bursch, Andreas Hansen, Matthias Brandl, Gabriele Sentis, Lukas Kunze, Michael Bolte, Hans-Wolfram Lerner, Stefan Grimme, Matthias Wagner: [Cl@Si20H20]−: Parent Siladodecahedrane with Endohedral Chloride Ion. J. Am. Chem. Soc., https://doi.org/10.1021/jacs.1c05598

University of Frankfurt press release: https://aktuelles.uni-frankfurt.de/forschung/neue-stoffklassen-fuer-nanomaterialien-nano-baelle-und-diamantsplitter-aus-silizium-und-germanium/

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