Hidden gapless states on the path to semiconductor nanocrystals

phys.org | 10/12/2018 | Staff
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When chemists from the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw were starting work on a new material designed for the efficient production of nanocrystalline zinc oxide, they didn't expect any surprises. They were thus greatly astonished when the electrical properties of the changing material turned out to be extremely exotic.

The single source precursor (SSP) approach is widely regarded as a promising strategy for the preparation of semiconductor nanocrystalline materials. However, one obstacle to the rational design of SSPs and their controlled transformation to the desired nanomaterials with highly controlled physicochemical properties is the scarcity of mechanistic insights during the transformation process. Scientists from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) and the Faculty of Chemistry of Warsaw University of Technology (WUT) now report that in the thermal decomposition process of a pre-organized zinc alkoxide precursor, the nucleation and growth of the semiconducting zinc oxide (ZnO) phase is preceded by cascade transformations involving the formation of previously unreported intermediate radical zinc oxo-alkoxide clusters with gapless electronic states. Up to now, these types of clusters have not been considered either as intermediate structures on the path to the semiconductor ZnO phase or as a potential species accounting for the various defect states of ZnO nanocrystals.

Groups - ZnO - Precursors - Decades - Zinc

"We discovered that one of the groups of ZnO precursors that have been studied for decades, zinc alkoxide compounds, undergo previously unobserved physicochemical transformations upon thermal decomposition. Originally, the starting compound is an insulator. When heated, it rapidly transforms into a material with conductor-like properties, and a further increase in temperature equally rapidly leads to its conversion into a semiconductor," says Dr. Kamil Sokołowski (IPC PAS).

The design and preparation of well-defined nanomaterials in a controlled manner remains a tremendous challenge, and is acknowledged to be the...
(Excerpt) Read more at: phys.org
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