Tuning the physico-chemical properties of SnSe films by pulse electrodeposition

SnSe is semiconductor with various applications in optoelectronic devices, but its synthesis still facing challenges. Here, an original approach to tune the morphology, the optical properties and microstructure of SnSe films is proposed, based on the change of pulse duration during electrodeposition. The syntheses were carried out at a unique applied potential of −0.55 V vs AgCl/Ag with pulse durations (t_ON) ranging from 50 ms to 500 ms. The microstructure was systematically studied with SEM, TEM, XRD and XPS characterizations. First, the formation of SnSe of compact films without pinholes is demonstrated, with no significant change of composition (Se/Sn ratio close to 1:1). All the films are crystalized according to the Pnma orthorhombic phase with a preferential growth direction perpendicular to the (1 1 1) direction. The increase of pulse duration from 50 to 500 ms reduces the crystallinity of film, but less Se and SnO₂ by-products are formed. Finally, the absorption coefficient of the films was extracted from ellipsometric measurements and evaluated in the near-edge region to evaluate the optical bandgaps. The results confirmed a slight change in the optical bandgap, from 1 to 1.1 eV. This work opens new alternative to tune physico-chemical properties of SnSe films.