Orientation-dependent ferroelectricity of strained PbTiO3 films

PbTiO3 is a simple but very important ferroelectric oxide that has been extensively studied and widely used in various technological applications. However, most previous studies and applications were based on the bulk material or the conventional [001]-orientated films. There are few studies on PbTiO3 films grown along other crystalline axes. In this study, a first-principles calculation was performed to compute the polarization of PbTiO3 films strained by SrTiO3 and LaAlO3 substrates. Our results show that the polarization of PbTiO3 films strongly depends on the growth orientation as well as the monoclinic angles. Further, it is suggested that the ferroelectricity of PbTiO3 mainly depends on the tetragonality of the lattice, instead of the simple strain.