Effect of structure architecture on optical properties of TiTe2/Sb2Te3 multilayer nanofilms

Heterostructural materials have the advantage of extreme low switching energy between states and hence are expected to be applied in photonic devices, whose optical performances are vital to explore in advance. In this paper, crystal structures of TiTe2/Sb2Te3 heterostructural films and their effects on optical properties were clarified from the aspects of in-plane strain, resonant bonding and charge redistribution by experiments and first principle simulations. Larger strain in Sb2Te3 sublayer tended to decrease reflectivity and refractive indexes, while huge resonant bonding effect was beneficial to improve the optical parameter deviations. Charge analyses showed that crystalline optical property variations were actually deriving from the electron redistribution differences especially near the heterostructural Te…Te gap, which also accounted for experimental reflectivity order. Finally, based on the resonant bond effects and surrounding electron density after stimuluses, five optical levels with identifiable optical contrasts (n and ΔR) were achieved in 1/2 model for uses. The present study sheds new light on optical properties of TiTe2/Sb2Te3 and paves the way for potential multi-state applications of heterostructure in photonic and storage devices.