The effect of biaxial strain on the band structure of two-dimensional silicon nanosheets (Si NSs) with (111), (110), and (001) exposed surfaces was investigated by means of density functional theory calculations. For all the considered Si NSs, an indirect-to-direct band gap transition occurs as the lateral dimensions of Si NSs increase; that is, increasing lateral biaxial strain from compressive to tensile always enhances the direct band gap characteristics. Further analysis revealed the mechanism of the transition which is caused by preferential shifts of the conduction band edge at a specific k-point because of their bond characteristics. Our results explain a photoluminescence result of the (111) Si NSs [U. Kim et al., ACS Nano 2011, 5, 2176-2181] in terms of the plausible tensile strain imposed in the unoxidized inner layer by surface oxidation.
Bibliographical noteFunding Information:
B.-H.K., M.P., G.K. and K.-R.L. acknowledge funding from the Nano Materials Development Program (2016M3A7B4025402). Grants from the National Research Foundation of Korea (NRF, Grant No. 2017K2A9A2A12000322) and the Swedish Foundation for International Cooperation in Research and Higher Education (STINT, Grant No. KO2016-6901) within their joint Korea-Sweden Research Cooperation program are gratefully acknowledged by B.-H.K. and K.-R.L. on the Korean side, and K.H. and P.B. on the Swedish side. This research was also funded by the Research and Development Program of Korea Institute of Energy Research (KIER) (B8-2453). The calculations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at UPPMAX and NSC.
© Copyright 2018 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films