Synthesis of an open-framework allotrope of silicon.
Silicon is ubiquitous in contemporary technology. The most stable form of silicon at ambient conditions takes on the structure of diamond (cF8, d-Si) and is an indirect bandgap semiconductor, which prevents it from being considered as a next-generation platform for semiconductor technologies. Here, we report the formation of a new orthorhombic allotrope of silicon, Si24, using a novel two-step synthesis methodology. First, a Na4Si24 precursor was synthesized at high pressure; second, sodium was removed from the precursor by a thermal 'degassing' process. The Cmcm structure of Si24, which has 24 Si atoms per unit cell (oC24), contains open channels along the crystallographic a-axis that are formed from six- and eight-membered sp(3) silicon rings. This new allotrope possesses a quasidirect bandgap near 1.3 eV. Our combined experimental/theoretical study expands the known allotropy for element fourteen and the unique high-pressure precursor synthesis methodology demonstrates the potential for new materials with desirable properties.
Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015, USA.
Duck Young
DY
Kim
Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015, USA.
Stevce
S
Stefanoski
1] Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015, USA [2] IMPMC, UPMC Sorbonne Universités, UMR CNRS 7590, Muséum National d'Histoire Naturelle, IRD UMR 206, 75005 Paris, France.
Oleksandr O
OO
Kurakevych
Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015, USA.
Timothy A
TA
Strobel