TDDFT studies on sheet size-dependency of optoelectronic properties of 2D silicon doped with alkali metals

Silicene, a two-dimensional (2D) silicon nanosheet, has gained immense interest due to potential applications, better compatibility, and expected integration with current silicon (Si) technology. This work explores the effects of silicene sheet size on its optoelectronic properties using Time-Dependent Density Functional Theory (TDDFT). Four structures of hydrogen-terminated silicene, Si13H22, Si19H30, Si54H74, and Si104H134 are investigated. It is observed that the structures have size tunable spectral response in the UV spectrum. The optimized sheets show a relatively smaller physical deformation compared to equivalent sized 2D Germanium sheets. IR spectra calculation of various bond vibrations show a good match with reported experimental results. The results show the potential for these 2D sheets to be effective optoelectronic materials in the visible spectrum, unlike bulk Si and Si nanowires. Furthermore, the effect of doping alkali metals (Li, Na and K) removing the H atoms in the silicene sheets were also investigated and their dipole moment and bond lengths are reported