Composition control and dielectric properties of bismuth zinc niobate thin films synthesized by radio-frequency magnetron sputtering

Radio-frequency sputtering was used to deposit near-stoichiometric ${\mathrm{Bi}}_{\text{1.5}}{\mathrm{Zn}}_{\text{1.0}}{\mathrm{Nb}}_{\text{1.5}}{\mathrm{O}}_7$ (BZN) films. Composition, crystallinity, and phase purity of the films were investigated by Rutherford backscattering spectrometry, x-ray diffraction, and transmission electron microscopy (TEM). X-ray diffraction detected cubic pyrochlore in films that were annealed above $\text{400\hspace{0.05em}°}\mathrm{C}.$ Films were fully crystallized at $\text{750\hspace{0.05em}°}\mathrm{C}.$ TEM and electron diffraction confirmed the cubic pyrochlore structure of the grains. Dielectric constant and loss were measured using planar ${\mathrm{Si/SiO}}_2/\mathrm{Pt/BZN/Pt}$ and ${\mathrm{Al}}_2{\mathrm{O}}_3/\mathrm{Pt/BZN/Pt}$ capacitor structures, respectively. After annealing at $\text{750\hspace{0.05em}°}\mathrm{C},$ films on Pt coated silicon wafers showed a permittivity of 170, low dielectric losses, and a large electric field tunability of the dielectric constant at a measurement frequency of 1 MHz. Dielectric loss tangents improved when substrates were moderately heated during deposition.