  Defect engineering is an effective and powerful tool to control existing
material properties and create completely new ones, which are
symmetry-forbidden in a defect-free crystal. This letter reports on the
creation of piezoelectrically active near-surface layer of centrosymmetric
SrTiO3, modified by the electric field-induced migration of oxygen vacancies.
We provide the unequivocal proof of piezoelectricity through the stroboscopic
time-resolved X-ray diffraction under alternating electric field. The magnitude
of the discovered piezoelectric effect is comparable with the bulk
piezoelectric effect in commercial ferroelectric materials. Such artificially
formed defect-mediated piezoelectricity can be important as an alternative road
for smart materials design.
