Prediction Of Two-dimensional Silicon Allotropes By First-principles Calculations

Silicene have attracted extensive research interset due to the fantastic physical properties and its integrated into the current Si-based semiconductor industry,which makes silicene a promising candidate for the future electronic devices.However,there are two problems for silicene.Firstly,the activity of silicene has strong and can only be prepared on substrates,and the interactions with the substrates have a distinct influence on the structural and electronic properties of silicene.In addition,the band gap of silicene is too small.It is found that searching for new stable two-dimensional silicon material is an effective way to overcome the difficulties of silicenee and expand the application of 2D silicon-based materials,except for tunning properties of silicene by absorption and edge-cutting.Based on the ab inito calculations,we have predicted two stable 2D silicon allotrops with large band gap.Their structural properties and stability were evaluated by calculations of their formation energy,phonon spectrum and molecular dynamics simulation.It was found that both two-dimensional silicon structures are more stable than silicene.Moreover,by studying their electronic properties,they were found to be wide band gap semiconductor materials.The band gaps of OTDS and(?)×(?)-DA were 1.5 eV and 1.1 eV,respectively.Our study provides useful theoretical basis for finding new silicene materials and expanding the application of silicene.