Electrochemical formation of nanometric layers of tin selenides on Ti surface

Photoelectrically active tin selenide coatings of nanometric thickness were manufactured by electrodeposition from separate solutions of Sn and Se precursors. Sn was deposited from acidic SnSO4 electrolytes and Se was deposited from H2SeO3 solutions. Fine-grained Sn coatings were deposited at potential φ = −0.3 V with 100% current efficiency. Se coatings were formed at two potentials: φ = −0.5 V, forming Se0, and φ = −0.85 V, forming Se2− ions. After the Sn coating was immersed into H2SeO3 solution, small quantities (∼2 at.%) of SnSe were formed and SeO32− was adsorbed on the surface. A short-time deposition of Se at φ = −0.5 V passivated the surface, so no Sn dissolution is observed upon anodic polarization. XPS and Auger data indicated that under those conditions 20 at.% of Se0 and only 2 at.% of SnSe were formed. Thickening of Sn and Se layers led to formation of larger quantities of Se0 (75 at.%) and SnSe (4–5 at.%) on the surface, whereas deeper layers contained up to 10 times more of SnSe phase. Upon deposition of Se at φ = −0.85 V, new SnSe2 phase was formed and the quantity of SnSe phase is increased and that of Se0 was reduced. All coatings formed exhibited photoelectric properties.