Abstract
The dielectric constant of ferroelectric material, (Pb,Ba)ZrO3, (PBZ) depends on dc voltages. Because of this tunable characteristic, it is applied to fabricate the varactors, tunable filters and phase shifter devices. The dielectric properties of the PBZ films deposited by RF- magnetron sputtering were investigated in this thesis. The sputtered PBZ film exhibits much higher tunability (60% at 200kV/cm) and only a little higher loss tangent (0.015) than the corresponding sol-gel PBZ films. (111) prefer-oriented PBZ thin film was successfully grown on BaPbO3 (BPO) buffer layer at temperatures once 400oC. Non-stoichiometry of Pb near the BPO interface was observed. The interface consisted of a Pb-rich interfacial layer of ~40nm. The thickness-dependent dielectric properties of Pt/PBZ/BPO capacitors can be attributed to (1) the interfacial layer at PBZ/BPO interface, (2) dead layer at Pt/PBZ interface, and (3) the grain boundary dead layersWith doping of Pt or Al2O3, the dielectric properties of PBZ films are greatly improved. The doped PBZ films possess low leakage current, low dissipation factor, and low temperature coefficient of capacitance. The best dielectric properties are J=1.32×10-8 A/cm2 (applied field : 1 MV/cm), tanδ=0.003, and TCC=1.13×10-4, respectively. The microwave dielectric properties were measured with a circular-patch capacitor geometry and a network analyzer (HP8753ES, Agilent). The results demonstrate that the sputtered PBZ films are promising materials for microwave device applications by optimum doping content and doping element.