A ferroelectric memory diodes that consists of Au/Pb(Zr0.52Ti0.48)O3/Bi4Ti3O12/p-Si multilayer configuration was fabricated by pulsed laser deposition (PLD) technique. The ferroelectric properties and the electrical characteristics of the ferroelectric film system were investigated. The polarization-voltage curve of Pb(Zr0.52Ti0.48)O3/Bi4Ti3O12 thin films system had an asymmetry hysteresis loop with Pr=20μC/cm2 and Ec=48 kV/cm, and the decay in remnant polarization was only 10% after 109 switching cycles. The C-V curve and the I-V curve showed memory effects derived from the ferroelectric polarization of PZT/BIT films. The current density was 6.7×10−8A/cm2 at a voltage of +4V, and the conductivity behavior is discussed. The results suggested that the growth of the BIT ferroelectric layer is helpful to good ferroelectric properties, fatigue and capacitance retention characteristics.

Ir-Ta-O composite bottom electrode has extraordinary high temperature stability. It can maintain good conductivity and integrity even after 5min annealing at 1000 °C in oxygen ambient. The thermal stability of Ir-Ta-O on different substrates has been studied. It shows that Ir-Ta-O is also very stable on Si and SiO2 substrates. No hillock formation and peelings of the bottom electrode were observed after high temperature and long time annealing in O2 ambient. SEM, TEM, XRD, and AES have been used to characterize the Ir-Ta-O film and the interfaces between Ir-Ta-O bottom electrode and Si or SiO2 substrate. The composition and conductivity changes of the electrode during oxygen ambient annealing and the interdiffusion issue will be discussed. Furthermore, Ir-Ta-O/SiO2/Si capacitor with 30Å gate oxide was fabricated and the C-V and I-V characteristics were measured to confirm the stability of Ir-Ta-O on thin gate oxide.

The degradation mechanism of Pb(Zr,Ti)O3 (PZT) under reducing conditions was revealed. In contrast to the significant decrease in the sample weight of SrBi2Ta2O9 due to decomposition, the weight of Pb(Zr,Ti)O3 samples change little during H2-annealing at typical process temperatures. Although no apparent changes were detected by thermogravimetric and x-ray diffraction measurements after annealing, the PZT material did actually change. The main mechanism of the degradation is introduction of oxygen defects into the materials. The oxygen defects produce a donor level within the band gap, and light absorption by this donor level accounts for the change in sample appearance from white to black. Different endurance behaviors of materials against reducing conditions were also found: PbZrO3 decomposes through oxygen dissociation more easily than PbTiO3. Oxygen atoms in PbZrO3 are more weakly bonded to Zr than to Ti in PbTiO3 because of a significant anti-bonding component in the hybridized orbitals.

X-ray diffraction was used to probe the structural changes associated with the conversion of the paraelectric phase to the ferroelectric phase that results from the application of a large external electric field. The samples under study are ultrathin (150 to 250 Å) Langmuir-Blodgett films of the copolymer vinylidene fluoride (70%) with trifluoroethylene (30%) deposited on aluminum-coated silicon. Theta-2theta X-ray diffraction was used to measure the change in inter-layer spacing perpendicular to the film surface. Upon heating at zero external electric field, the crystalline films undergo a structural phase transition, at 100± 5°C, from the all-trans ferroelectric phase to the trans-gauche paraelectric phase. [1,2] Above the phase transition temperature, the non-polar paraelectric phase can be converted back to the polar ferroelectric phase, in a smooth continuous process, using a large external electric field (∼1 GV/m). For example, at 100° C the ferroelectric phase first appears above 0.2 GV/m and increases steadily in proportion while the paraelectric phase decreases until complete conversion to the ferroelectric phase is achieved at approximately 0.6 GV/m.

MFMOS and MFOS (M: Metal, F: Ferroelectrics, O: Oxide, S: Silicon) capacitors with high k gate oxides, such as ZrO2, HfO2 thin films, have been fabricated for one transistor memory applications. Experimental results showed that ZrO2 and HfO2 have no serious reaction or diffusion into silicon substrate. Due to their high dielectric constant, the operation voltages of MFMOS capacitors are reduced. The MFMOS capacitor exhibits 2V memory window. For lead germanium oxide (PGO) on ZrO2 and PGO on HfO2 MFOS memory cells the memory windows are 1.8 V and 1.6 V, respectively, which are large enough for one-transistor memory applications. The basic mechanism for one-transistor memory applications was also discussed.

(1°x)Pb(Yb1/2Nb1/2)O3划xPbTiO3 (PYbN-PT, x=0.5) epitaxial films were grown on (001)SrRuO3/(001)LaAlO3 and (111)SrRuO3/(111)SrTiO3 substrates by pulsed laser deposition. (001)PYbN-PT epitaxial films with high phase purity and good crystalline quality were obtained for a wide range of deposition rates (60-90 nm/min) and temperatures (620-680 °C). (111)PYbN-PT films were also obtained at temperatures in the range of 600 °C to 620 °C. The ferroelectric and piezoelectric properties were investigated on both (001) and (111) PYbN-PT films. The remanent polarizations of (001)PYbN-PT and (111)PYbN-PT films were as high as 34 μC/cm2 and 26 μC/cm2, respectively. On (001)PYbN-PT films with a thickness of 900 nm, an e31 coefficient of -13 C/m2 and an aging rate of 2.5% per decade were observed.

Electrical characteristics of ferroelectric thin films in planar electrode configuration are important to characterize these materials for their applications in micro electro mechanical (MEM) and tunable microwave devices. In the present work we have prepared polycrystalline Pb1划3x/2Ndx(Zr0.53Ti0.47)O3 (x = 0.0 to 10.0 at %) thin films on platinized silicon substrate by chemical solution deposition (CSD) technique. The films were characterized in terms of their dielectric and ferroelectric properties by depositing planar interdigital finger electrodes on the surface of the films by electron beam lithography. The capacitance and loss tangent of undoped and 4 at % Nd doped PZT films measured at 100 kHz were found to be 138 pF, 0.033 and 95 pF, 0.019 respectively. Saturated hysteresis loops were obtained in undoped PZT film by applying 100 V across 10 μm electrode separation. Nd doped PZT films on the other hand, electrically shorted at comparatively lower voltage. The electrical characteristics of these films are correlated with their phase formation behavior and microstructural features.

The understanding of the polarization switching process of ferroelectric capacitors is highly relevant for the development and optimization of FeRAM devices. We report on the characterization of Pb(Zr,Ti)O3 thin films which have been studied by means of dedicated rectangle pulse measurements. Decreasing the voltage level of the excitation pulses decelerates the polarization switching significantly to the range of milliseconds and reduces the switchable polarization. In this work the influence of niobium (Nb) doping on the switching properties of PZT thin films prepared by CSD are investigated to reach the aspired conditions of low voltage operation, read and write access pulses in the range of nanoseconds. For the implementation of the transient behavior of ferroelectric capacitors in circuit design and simulation tools it is necessary to develop a model which precisely describes the polarization hysteresis, the pulse switching behavior as well as the small signal capacitance. The fundamental considerations for this model are presented, based on an ideal ferroelectric capacitor, taking into account the Curie-von Schweidler behavior. The latter is observed in non-ferroelectric high-K materials as well as in ferroelectric thin films.

Ir films were prepared on SiO2/Si at 275-500°C by M°CVD (Metalorganic Chemical Vapor Deposition) using a new Ir precursor, Ir(EtCp)(cod) (iridium(ethylcyclopentadienyl) (1,5-cyclo°Ctadiene): Ir(C2H5C5H4)(1,5-C8H12). Ir films prepared at 275-300°C showed highly reflecting surfaces with Rrms roughness (root-mean-square roughness) of 1.4-10nm. At 500°C, Ir and IrO2 mixture-oriented films were grown. Ir films deposited at 300°C on patterned SiO2/Si substrates with aspect ratios of 0.3-2.0 showed good step coverage of 70-85%. Auger analysis revealed that Ir film had no incorporation of carbon and oxygen, and that Ir films performed well as a diffusion barrier in PZT/Ir/SiO2/Si structure.

Epitaxial (001)-, (116)- and pseudo (103)-oriented Sr0.35Bi2.2Ta2O9 (SBT (0.35/2.2/2.0)) films were successfully grown on (001), (110) and (111) SrTiO3 substrates, respectively. High-resolution X-ray diffraction reciprocal space mapping (HRXRD-RSM) measurements and pole figure measurements clearly indicated that the (116)-oriented SBT (0.35/2.2/2.0) film consisted of two growth domains those c-axis are separated 180° apart in in-plane and pseudo (103)-oriented SBT film consisted of three growth domains those c-axis are separated 120° apart in in-plane. Moreover, lattice parameter measurements indicated that SBT films grew in fully relaxed state.

Pulsed laser deposition (PLD) was used to growth thin films of lead zirconium titanate (PZT) and lead zinc niobate-barium titanate (PZN-BT). The PZT films were prepared from commercial PZT-5H ceramic target and the PZN-BT made from target made using a modified Columbite method. The PZT films had dielectric constants of 300 and loss of 0.03 at 10kHz, whilst for the PZN-BT films they were 350 and 0.03 respectively at 300K. Hysteresis measurements confirmed their switching properties

A piezoresponse microscope based on a modified atomic force microscope was developed to determine electromechanical response at a sub-micrometer resolution. The PZT films yielded d33 ∼100pm/V. Mapping measurements on the PZT demonstrated local switching of individual grains. First measurements of piezoresponse of PZN-BT yielded values in the region 150-200 pm/V.

(Ba,Sr)TiO3 [BST] films were deposited by the flash vaporization CVD method with a unique liquid delivery system. An inductively coupled plasma mass spectrometry [ICP-MS] analysis revealed the decline of (Ba+Sr)/Ti molar ratio of the initial BST-layer on Ru. By readjusting the flow ratio of liquid sources and using a two-step deposition method, we obtained 30-nm-thick BST films with uniform composition profile, exhibiting good electrical properties. The leakage property, however, was severely deteriorated in BST films less than 24 nm thick. A SEM observation showed the presence of micro-roughness or micro-hillocks in these films, which were confirmed to be caused by Ru oxidation. Therefore, an annealing process of the Ru electrode was added for its planarization, and the CVD process was also improved. As a result, we obtained smooth and finely crystallized ∼ 20-nm-thick BST films with good electrical properties of equivalent SiO2 thickness (teq) ∼ 0.45 nm and leakage current < 1 × 10−7 A/cm2. We also measured properties of BST films deposited on the 3-D Ru electrode. The results are briefly discussed.