The influence of vicinal SrTiO3 surfaces on the growth and ferroelectric properties of epitaxial Bi4Ti3O12 thin films

Adsorption-controlled growth conditions have been utilized to grow epitaxial, stoichiometric, c-axis oriented Bi4Ti3O12 thin films by reactive molecular beam epitaxy (MBE). We have studied samples grown on vicinal (miscut) and well-oriented (100) SrTiO3 substrates. There is a degradation in film properties as a function of step density (degree of miscut) on the SrTiO3 surface. The greater the degree of miscut of the SrTiO3 substrate, the less intense the X-ray diffraction peak intensities of the film become, and the wider are the rocking curve widths. The reduced film quality is further confirmed by ferroelectric hysteresis measurements. Films grown on miscut substrates have significant space charge contributions to the polarization, while films grown on well-oriented substrates show symmetric hysteresis loops with remanent polarizations approaching values obtained for bulk single crystals. The degradation of film properties is explained by considering the influence of steps at the SrTiO3 substrate surface on the electronic and crystallographic continuity in the ab plane of the deposited Bi4Ti3O12 films.