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The structural, microstructural, and surface morphological properties of Ba 0.5 Sr 0.5 TiO 3 thin films were investigated as a function of Ni dopant concentration. The Ni-dopant concentration in BST films has a strong influence on the material properties including dielectric and tunable properties as well as film growth rate. Ni doped (≤3 mol%) BST films showed denser, smoother, and smaller grain sizes than those with 6 and 12 mol% Ni. Dielectric constant and loss of 3 mol% Ni-doped BST films were about 980 and 0.3%, respectively. In addition, tunability and figure of merit of 3 mol% doped BST films showed maximum values of approximately 39% and 108, respectively. Correlation of the material properties with dielectric and tunable properties suggests the the 3 mol% Ni-doped BST films are the optimal choice for tunable device applications.

Articles you may be interested inAnomalous leakage current characteristics of Pt/(Ba 0.75 , Sr 0.25 ) Ti 1+y O 3+z / Pt thin films grown by metalorganic chemical vapor deposition

Electrode structures of Pt/RuO2/Ru on polysilicon and (Ba,Sr)TiO3(BST) thin films on Pt/RuO2/Ru/poly-Si structures were prepared by metal-organic chemical vapor deposition (MOCVD). The barrier layers of RuO2/Ru deposited by MOCVD showed a stable interface and did not affect the surface morphology of the platinum bottom electrode even at a high annealing temperature of 800°C in oxygen ambient. Contacts in the annealed state up to 800°C exhibited linear current-voltage characteristics with a constant specific contact resistance of 5.0 ×10-5 Ω·cm2. The excellent leakage current characteristics and dielectric properties of 50-nm-thick BST films were due to the stable and smooth morphologies of the bottom electrodes at BST deposition temperature.

The effect of hydrogen on ferroelectric properties was investigated for ͑Pb, La͒͑Zr, Ti͒O 3 ͑PLZT͒ films with Pt and IrO 2 top electrodes. The P-E hysteresis loop and fatigue properties of the Pt/PLZT/Pt capacitor are completely recovered by recovery anneal at 700°C in O 2 ambient after a hydrogen-forming gas anneal. On the other hand, IrO 2 /PLZT/Pt capacitor after recovery anneal does not show a complete recovery for ferroelectric properties. The IrO 2 top electrode in the IrO 2 /PLZT/Pt capacitor is completely reduced to Ir metal in 4% H 2 at 300°C and then change to the IrO 2 /Ir complex phase after recovery anneal at 700°C in O 2 ambient. The ferroelectric properties of PLZT capacitors greatly depend on the residual hydrogen near the film/top electrode interface after recovery anneal.The choice of electrode materials used in conjunction with Pbbased ferroelectric thin films strongly influences the structural and electrical properties. Recently, Ir and IrO 2 have attracted attention as electrode materials for Pb͑Zr, Ti͒O 3 ͑PZT͒ and ͑Pb, La͒͑Zr, Ti͒O 3 ͑PLZT͒ thin film capacitors since they showed ferroelectric properties with higher quality than Pt/PZT/Pt capacitors. In addition, PZT capacitors with hybrid bottom electrode structures, such as Pt/IrO 2 and Ir/IrO 2 have been reported. 1-4 One of the processing issues that is receiving considerable attention in the integration of ferroelectric capacitors on Si is a low temperature forming gas anneal. Unfortunately, both PZT and SrBi 2 Ta 2 O 9 ͑SBT͒ ferroelectric thin film capacitors with Pt top electrodes lose their polarization hysteresis characteristics as a result of such an anneal. 5 It has been reported that dissociative adsorption of the hydrogen atoms or protons by the catalytic activity of Pt play critical roles in degrading the ferroelectric properties 6-8 and leakage current densities 9 of SBT and PZT thin films. On the other hand, the use of IrO 2 as the top electrode in PZT capacitors offers an opportunity to suppress the degradation because it does not have a catalytic effect. However, an as-grown IrO 2 top electrode was easily reduced to Ir metal by a hydrogen annealing at 300°C which simulates a process condition of interlayer dielectric deposition. 10 Ramesh et al. reported that even a bare La 0.5 Sr 0.5 CoO 3 ͑LSCO͒ top electrode can prevent the complete loss of ferroelectricity during forming gas treatment. 11 Therefore, in this study, the impact of Pt and IrO 2 top electrodes on capacitor properties annealed in H 2 and recovered in O 2 ambients is reported, with particular emphasis on P-E hysteresis and fatigue properties. The Pt͑top͒/PLZT/Pt and IrO 2 ͑top͒/PLZT/Pt capacitors are annealed in H 2 at 300°C and recovered at 700°C in O 2 ambients. ExperimentalPLZT (Zr:Ti ratio ϭ 30:70) thin films with 3% La dopant concentration were prepared using a chemical solution deposition ͑CSD͒ method. Approximately 12% excess lead was added to the precursor solution to compensate for the loss of lead oxide during the final annealing process. Films were ...