Preference for a propellane motif in pure silicon nanosheets

Abstract

Free standing silicene nanosheets remain elusive presumably due to the instability associated with sp² hybridized silicon atoms. Here we show that silicon prefers nanosheets based on the non-classical Si₅ unit with a [1.1.1]-propellane motif that has two inverted tetrahedral atoms bridged by three tetrahedral atoms. DFT calculations show that nanosheets constructed exclusively from propellane building blocks are consistently more stable than those with sp² silicon atoms or their hybrids. These nanosheets also exhibit a narrow but definite band gap, unlike those reported earlier.