One imaginative and prescient that’s presently driving materials scientists is to mix natural molecules (and their numerous functionalities) with the technological prospects provided by extraordinarily subtle semiconductor electronics. Thanks to trendy strategies of micro- and nanotechnology, the latter designs ever extra environment friendly digital elements for all kinds of purposes. However, it’s also more and more reaching its bodily limits: Ever smaller buildings for functionalizing semiconductor supplies resembling silicon can’t be produced utilizing the approaches of classical expertise. Scientists have now offered a brand new method within the journal Nature Chemistry: They present that steady and but very well-ordered molecular single layers could be produced on silicon surfaces — by self-assembly. To do that, they use N-heterocyclic carbenes. These are small reactive natural ring molecules whose construction and properties fluctuate in some ways and could be tailor-made by completely different “practical” teams.
Researchers led by Prof. Dr. Mario Dähne (TU Berlin, Germany), Prof. Dr. Norbert Esser (TU Berlin and Leibniz Institute for Analytical Sciences, Germany), Prof. Dr. Frank Glorius (University of Münster, Germany), Dr. Conor Hogan (Institute of Structure of Matter, National Research Council of Italy, Rome, Italy) and Prof. Dr. Wolf Gero Schmidt (University of Paderborn, Germany) had been concerned within the examine.
Technological miniaturization reaches its limits
“Instead of making an attempt to artificially produce smaller and smaller buildings with rising effort, it’s apparent to be taught from molecular buildings and processes in nature and to merge their performance with semiconductor expertise,” says chemist Frank Glorius. “This would make an interface, so to talk, between molecular operate and the digital consumer interface for technical purposes.” The prerequisite is that the ultra-small molecules with variable construction and performance must be bodily included with the semiconductor gadgets, they usually must be reproducible, steady and so simple as doable.
Harnessing the self-organization of molecules
The self-organization of molecules on a floor, as an interface to the machine, can carry out this activity very properly. Molecules with an outlined construction could be adsorbed on surfaces in massive numbers and organize themselves right into a desired construction that’s predetermined by the molecular properties. “This works fairly properly on surfaces of metals, for instance, however sadly under no circumstances satisfactorily for semiconductor supplies to date,” explains physicist Norbert Esser. This is as a result of so as to have the ability to organize themselves, the molecules should be cellular (diffuse) on the floor. But molecules on semiconductor surfaces don’t try this. Rather, they’re so strongly sure to the floor that they stick wherever they hit the floor.
N-Heterocyclic carbenes as an answer
Being concurrently cellular and but stably bonded to the floor is the essential drawback and on the identical time the important thing to potential purposes. And it’s exactly right here that the researchers now have a doable answer at hand: N-heterocyclic carbenes. Their use for floor functionalization has attracted a number of curiosity over the previous decade. On surfaces of metals resembling gold, silver and copper, for instance, they’ve confirmed to be very efficient floor ligands, usually outperforming different molecules. However, their interplay with semiconductor surfaces has remained just about unexplored.
Formation of a daily molecular construction
Certain properties of the carbenes are decisive for the truth that it has now been doable for the primary time to supply molecular single layers on silicon surfaces: N-heterocyclic carbenes, like different molecules, type very sturdy covalent bonds with silicon and are thus stably sure. However, aspect teams of the molecule concurrently preserve them “at a distance” from the floor. Thus, they will nonetheless transfer about on the floor. Although they don’t journey very far — just a few atomic distances — that is ample to type an nearly equally common molecular construction on the floor of the frequently structured silicon crystal.
Using a complementary multi-method method of natural chemical synthesis, scanning probe microscopy, photoelectron spectroscopy and complete materials simulations, the researchers clarified the precept of this novel chemical interplay of their interdisciplinary collaboration. They additionally demonstrated the formation of standard molecular buildings in a number of examples. “This opens a brand new chapter for the functionalization of semiconductor supplies, resembling silicon on this case,” emphasizes physicist Dr. Martin Franz, first creator of the examine.