Artificial design for new ferroelectrics using nanosheet-architectonics concept

Control over the emergence of ferroelectric order remains a fundamental challenge for the rational design of artificial materials with novel properties. Here we report a new strategy for artificial design of layered perovskite ferroelectrics by using oxide nanosheets (high-k dielectric Ca<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf> and insulating Ti<inf>0.87</inf>O<inf>2</inf>) as a building block. We approached the preparation of superlattice films by a layer-by-layer assembly involving Langmuir-Blodgett deposition. The artificially fabricated (Ti<inf>0.87</inf>O<inf>2</inf>/Ca<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf>)<inf>2</inf>(Ti<inf>0.87</inf>O<inf>2</inf>) superlattices are structurally unique, which is not feasible to create in the bulk form. By such an artificial structuring, we found that (Ti<inf>0.87</inf>O<inf>2</inf>/Ca<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf>)<inf>2</inf>(Ti<inf>0.87</inf>O<inf>2</inf>) superlattices possess a new form of interface coupling, which gives rise to ferroelectricity with a good fatigue-free characteristic. Considering the flexibility of self-assembled nanosheet interfaces, this technique provides a route to synthesize a new kind of layered ferroelectric oxides.