Effect of oxygen to argon ratio on properties of (Ba,Sr)TiO3 thin films prepared by radio-frequency magnetron sputtering

Thin films of (Ba,Sr)TiO3 on Pt/SiO2/Si substrates were deposited using rf magnetron sputtering at various substrate temperatures and O-2/(Ar + O-2) mixing ratios (OMR). The crystallinity of the films improved significantly as the OMR increased. The dielectric constant increased with increasing OMR and reached a maximum value at 50% OMR. The leakage current density decreased with increasing oxygen flow, but had a minimum value at 40% OMR. The results for the dielectric constant and the leakage current were interpreted in terms of polarization effect and loss theory, The film deposited at 450 degrees C and 50% OMR exhibited good surface morphology add had a dielectric constant of 375, a tangent loss of 0.074 at 100 kHz, a leakage current density of 7.35 X 10(-9) A/cm(2) at an electric field of 100 kV/cm with a delay time of 30 s, and a charge storage density of 49 fC/mu m(2) at an applied field of 150 kV/cm. The 10 yr lifetime of time-dependent dielectric breakdown studies indicate that a 50% OMR sample has a longer lifetime than the 0% OMR sample. (C) 1997 American Institute of Physics.