Effects of sputtering pressure on the properties of BaTiO₃ films for high energy density capacitors

Flexible BaTiO₃ films as dielectric materials for high energy density capacitors were deposited on polyethylene terephthalate (PET) substrates by r.f. magnetron sputtering. The growth behavior, microstructure and electrical properties of the flexible BaTiO₃ films were dependent on the sputtering pressure during sputtering. The RMS roughness and crystallite size of the BaTiO₃ increased with increasing sputtering pressure. All BaTiO₃ films had an amorphous structure, regardless of the sputtering pressures, due to the low PET substrate temperature. The composition of films showed an atomic ratio (Ba:Ti:O) of 0.9:1.1:3. The electrical properties of the BaTiO₃ films were affected by the microstructure and roughness. The BaTiO₃ films prepared at 100 mTorr exhibited a dielectric constant of ~80 at 1 kHz and a leakage current of 10^-8A at 400 kV/cm. Also, films showed polarization of 8 μC/cm² at 100 kV/cm and remnant polarization (P_r) of 2 μC/cm². This suggests that sputter deposited flexible BaTiO₃ films are a promising dielectric that can be used in high energy density capacitors owing to their high dielectric constant, low leakage current and stable preparation by sputtering.