What is it about?
What does a molecule do when it comes in contact with a very hot surface? We found an answer by studying the high-temperature behaviour of a copper complex on a silica substrate. The question is important because the decomposition of molecules on heated surfaces is a technologically strategic process at the basis of many applications. For instance, in Chemical Vapor Deposition (CVD), the source compounds (the "precursors"), are initially brought into the vapour phase; then, they react on a surface heated at a temperature much higher than that of the carrier vapour phase. At these conditions, activation mechanisms strongly different from those typical of gas-phase or solution chemistry are possible, and novel materials may be synthesized.
Why is it important?
We detected a new type of surface motion, defined as fast rolling diffusion on the hot surface (T=750 K). This molecular cart-wheeling motion (see movies) was combined with large oscillations of the metal-ligand bond lenghts: the molecule was therefore activated for the decomposition process. Indeed, this type of diffusion might also promote high-energy collisions between rolling molecules on the growth surface. These events could lead to precursor fragmentation and then formation of the first bonds between the metallic centers and the atoms of the growth surface.
The following have contributed to this page: Gloria Tabacchi
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