Enhanced conductivity and metal-insulator transition of ultrathin CaRuO₃ in superlattices

Transport characteristics of CaRuO₃(CRO)/SmFeO₃(SFO) superlattices are studied as a function of the thickness ofCRO(0.8 nm≤^tCRO≤3.2 nm). An abrupt enhancement of the conductivity is observed on superlattices, although ultrathinCROfilm show a very high resistance and SFO single layer is insulating. The superlattices with tCRO between 2.0 and 3.2 nmretain a metallic state. As tCRO decreases to 1.6 nmor even thinner in superlattices, the metallic state turns to insulating state. The metal-insulator transition could be attributed to the comparable scale for the disorder length and the electron travel distance at small tCRO value, which causes a change from weak localization to strong localization.