Dielectric properties of hybrid MBE-grown Sn-alloyed BaTiO₃ films

Lead-based perovskite oxides such as PMN-PT and PZT have been frontrunners for piezoelectric transducers and non-volatile ferroelectric memories due to their high piezoelectric coefficients and dielectric constants. A key ingredient for lead-free alternatives with these properties is the presence of morphotropic phase boundaries (MPBs). Sn-alloyed BaTiO₃ (BaTi_1-xSn_xO₃) is a promising candidate since it hosts a quasi-quadruple point at x = 0.11, resulting in 5-6-fold higher piezoelectric coefficients and dielectric constants than BaTiO₃ ceramics. [1]

We grow all-epitaxial SrRuO₃/BaTi_1-xSn_xO₃/SrRuO₃ heterostructures on Nb-doped SrTiO₃ (001) and GdScO₃ (110) substrates with hybrid molecular beam epitaxy (hMBE) using hexamethylditin and titanium tetraisopropoxide as sources for Sn and Ti respectively. Grazing incidence X-ray reflectivity shows superlattice oscillations suggesting smooth interfaces between the metal and ferroelectric layers. We fabricated capacitors from the ~ 50 nm BaTi_1-xSn_xO₃ films and observed a two-fold increase in the dielectric constant of BaTiO₃ at 300 K with a small addition of Sn. We discuss the effect of epitaxial strain and Sn incorporation on the dielectric and ferroelectric properties of BaTi_1-xSn_xO₃ films using impedance spectroscopy and P-E curves.



[1] Y. Yao et al., EPL 98, 27008 (2012)