Reducing the dimensionality of novel materials: one-dimensional silicon nanoribbons

Our group has revealed an unprecedented one-dimensional (1D) Si atomic arrangement solely comprising highly perfect alternating pentagons residing in the missing row troughs of the reconstructed surface Ag(1 1 0). It is the first pure pentagonal phase ever found for silicon low-dimensional structures, initially theoretically supported by density functional theory (DFT) calculations compared to scanning tunneling microscopy observations, further rapidly confirmed by surface X-ray diffraction measurements. In fact, until now such a structure has only been obtained synthetically as 1D nanoribbons (1D-NRs) grown on a silver (1 1 0) substrate. These NRs adopt a highly ordered chiral arrangement in single- and/or double-strands. We thus simultaneously demonstrate the existence of penta-silicene, a recently conjectured novel pentagonal silicon allotrope, which remained unveiled for more than one decade, and which materializes a paradigmatic shift from normal hexagonal silicene. The discovery of 1D-penta-silicene NRs increases the chances of the future isolation of this new low-dimensional Si allotrope, provided these epitaxial NRs can be detached from the silver surface.