Role of fluorine in two-dimensional dichalcogenide of SnSe2

Authors report an effect of F substitution on layered SnSe2 through the successful synthesis of polycrystalline SnSe2−δFx (0.000 ≤ x ≤ 0.010) by solid-state reaction. Accompanied with density functional theory calculations, the blue shift of A1g peak in Raman spectra reveal that F− ions are substituted at Se vacancy sites as decreasing the reduced mass of vibrational mode associated with Sn–Se bonding. From the measurements of electrical parameters, conductivity as well as carrier concentration are governed by thermally activated behavior, while such behavior is suppressed in Hall mobility, which occurs as F ratio increases. Based on Arrhenius relation, it is found that the potential barrier height at the grain boundary is suppressed with increasing F amount, suggesting that the F− ion is a promising candidate for the grain boundary passivation in the two-dimensional dichalcogenide system.