Effect of intercalated lithium on the electronic band structure of indium selenide

The effect of intercalated lithium on the electronic band structure of the β and γ polytypes of InSe has been investigated using a tight-binding method. The energy bands of the pure polytypes were calculated and the results compared with previous work. The tight-binding parameters associated with intercalated lithium atoms were obtained using tabulated atomic functions. The modifications of the energy bands produced by the introduction of one lithium atom per formula unit ${\mathrm{In}}_2$ ${\mathrm{Se}}_2$ were calculated for the lowest potential-energy position of the lithium atom in the van der Waals gap between layers. The intercalation-induced changes in the smallest and next-to-smallest direct band gaps were determined and compared with experimental data. An interpretation of a photoluminescence peak produced by lithium intercalation is given.