(a) Capacitance measured at 100 kHz as a function of applied bias on BTO films grown at different oxygen pressures. Curves at P = 14–200 mTorr have been shifted (2 μF/cm² shift between data sets) for clarity. (b) Variation with oxygen pressure (pO₂) of the coercive electric field (top panel) and of the dielectric constant at the maximum of C-V curve (squares) and at maximum applied voltage (triangles).