Combining structural and functional measurements, we have mapped the phase diagram of BiFeO3/LaFeO3 superlattices grown by off-axis sputtering on (110)o DyScO3 substrates. The phase diagram displays three distinct regions as a function of BiFeO3 fraction, with a BiFeO3-like ferroelectric phase and a LaFeO3-like paraelectric phase at its extremities, and a complex intermediate region, as supported by first-principles calculations. This intermediate region shows unusual, mixed functional behavior, most likely due to competing phases driven by substitution with a same-size central ion and the specific boundary conditions imposed by the superlattice structure. In the BiFeO3 rich superlattices, scaling of the ferroelectric-to-paraelectric transition temperature with the BiFeO3 thickness could provide an alternate route for studying ferroelectric size effects in BiFeO3.

The growth of atomically-flat thin films of ferroelectric PbTiO3 on SrTiO3 substrates, using molecular beam epitaxy, is reported. The main issue in the growth of these materials is the high volatility of lead. This can be largely overcome by using PbO, instead of Pb, as a source and by using atomic oxygen during growth. The continuous decrease of the out-of-plane lattice parameter with increasing temperature in the investigated range, indicates that PbTiO3 is still ferroelectric at the growth temperature (Tg= 600oC), which agrees with the theoretical prediction of TC= 765oC (compared to TCbulk= 490oC) for the present mismatch strain values.