Abrupt PbTiO3/SrTiO3 superlattices grown by reactive molecular beam epitaxy

${\mathrm{PbTiO}}_{\mathrm{3}}{\mathrm{/SrTiO}}_{\mathrm{3}}$ superlattices were grown on (001) ${\mathrm{SrTiO}}_{\mathrm{3}}$ substrates by reactive molecular beam epitaxy (MBE). Sharp superlattice reflections were observed by x-ray diffraction. High-resolution transmission electron microscopy of a $[{\mathrm{(PbTiO}}_{\mathrm{3}}{\mathrm{)}}_{\mathrm{10}}{\mathrm{/(SrTiO}}_{\mathrm{3}}{\mathrm{)}}_{10}{]}_{15}$ superlattice revealed that the ${\mathrm{PbTiO}}_{\mathrm{3}}{\mathrm{/SrTiO}}_{\mathrm{3}}$ interface structure is atomically sharp. The superlattice interfaces are fully coherent; no misfit dislocations or other crystal defects were observed in the superlattice by transmission electron microscopy. Selected area electron diffraction patterns indicated that the ${\mathrm{PbTiO}}_{\mathrm{3}}$ layers are oriented with the c axis parallel to the growth direction. The dimensional control and interface abruptness achieved in this model system indicate that MBE is a viable method for constructing oxide multilayers on a scale where enhanced dielectric effects are expected.