Tuning and optimizing properties of ferroelectric films grown on a single substrate: A first-principles-based study

摘要

A first-principles-based effective Hamiltonian is used to reveal the effects of the growth direction on properties of films made of the prototype of ferroelectric materials (namely, BaTiO_3) and grown on one of the most common and available substrates (that is, SrTiO_3. Continuously varying the growth direction from the pseudocubic [001 ] to [110] direction, via the high-symmetry [111] direction, results in (ⅰ) an original temperature-versus-growth angle phase diagram possessing different structural states, (ⅱ) a tuning of the Curie temperature T_c by more than 450 K, (ⅲ) a minimal value of T_c being near room temperature, and (ⅳ) optimization of important physical responses at room temperature, such as dielectric and piezoelectric coefficients, for some specific growth directions. The origins of these features are also revealed, including the finding of a law correlating T_c with the growth direction.