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

Abstract

Thin films of ${\mathrm{(Ba,Sr)TiO}}_{\mathrm{3}}$ on ${\mathrm{Pt/SiO}}_{\mathrm{2}}\mathrm{/Si}$ substrates were deposited using rf magnetron sputtering at various substrate temperatures and ${\mathrm{O}}_{\mathrm{2}}{\mathrm{/(Ar+O}}_{\mathrm{2}}\mathrm{)}$ 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 °C and 50% OMR exhibited good surface morphology and had a dielectric constant of 375, a tangent loss of 0.074 at 100 kHz, a leakage current density of ${\text{7.35×10}}^{\text{−9}}\hspace{0.17em}{\mathrm{A/cm}}^{\mathrm{2}}$ at an electric field of 100 kV/cm with a delay time of 30 s, and a charge storage density of $\text{49\hspace{0.17em}}{\mathrm{fC/\mu m}}^{\mathrm{2}}$ 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.