PZT (Zr/Ti = 53/47), PNZT (4% Nb doped PZT), PSZT (2% Sc doped PZT), and PSNZT (1% Sc and 1% Nb doped PZT) thin films were prepared by a sol-gel process. They were characterized by XRD, SEM and TEM. Both crystallographic orientation and grain size of PZT films can be changed by doping. Pt/PZT/Pt capacitors were fabricated for the measurement of ferroelectric properties. By doping with both Sc and Nb, the fatigue performance of the PZT films was considerably improved and the coercive field was decreased, while the remanent polarization was not changed. In addition, the effect of dopants on the leakage current level of PZT films was studied.

We report the preparation of PbZrxTi1−xO3 (PZT) films on Si substrates with a SrTiO3 (STO) buffer layer. STO buffer layers and PZT films were formed on Si substrates by the electron-beam assisted vacuum evaporation technique and sol-gel technique, respectively. By evaporating a thin (8nm) metal Sr layer prior to the STO deposition, which deoxidizes the SiO2 layer at the Si surface, (100)- and (111)-oriented STO thin films can be grown on Si(100) and (111) substrates, respectively. It is shown that a strongly (100)-oriented PZT film is grown on STO(100)/Si(100), whereas a strongly (111)-oriented PZT film is obtained on STO(111)/Si(111). It is also found that the STO buffer layer remains intact even after the PZT deposition. Secondary ion mass spectrometry (SIMS) analysis showed that the STO barrier layer was effective in preventing diffusion of Pb into the Si substrate.

There has not been much exploration of PLZT film properties as a function of compostion reported in the literature. A survey of numerous PLZT films covering a wide spectrum of the PLZT phase diagram was undertaken to explore the dependence of film properties on composition. A series of sol-gel derived PLZT films were prepared on platinized Si wafers and fired to 700C to obtain the perovskite phase. The film compositions include PLZT x/65/35, x/20/80, x/53/47 for x = 0, 2, 4, 6, 8, 10 and 12 and 7.5/x/y where x/y = 70/30, 53/47, 20/80 and 0/100. These films were characterized for their dielectric and ferroelectric properties. The films definitely showed a strong dependence of final film properties on composition, providing a valuable tool for the material engineering of ferroelectric film properties.

Tetragonal, perovskite type, powders and thin films of PbTiO3 have been synthesized by the sol-gel method, using trihydrate lead acetate and titanium tetraisopropoxide as starting alkoxides. The thermal treatment has been established from differential thermal and thermogravimetric analysis. An interpretation is presented for the various processes occurring during the gel to dense oxide conversion. The optimal process towards thin films includes annealing stages at 180, 400 and 650°C. Thin films were prepared by spinning on Si and Pt-covered Si. By SEM analysis the films appear cracked, porous, or homogeneous, with 0.5 to 1 um per solution coating. Current-voltage characteristics of Al/PT/Pt/Si capacitors exhibit a resistivity of 0.5 to 20·108Ωm, nondestructive breakdown in the range of 4 to over 20V, and relative dielectric permittivity of 100.

The (100), (111) and randomly oriented PZT thin films were fabricated on Pt/Ti/Coming 7059 glass using sol-gel method. The thin films having different orientation were fabricated by different drying conditions for pyrolysis. The preferred orientations of the PZT thin films were observed using XRD, rocking curves, and pole figures. The microstructures were investigated using SEM. The hysteresis loops and capacitance-voltage characteristics of the films were investigated using a standardized ferroelectric test system. The dielectric constant and current-voltage characteristics of the films were investigated using an impedance analyzer and pA meter, respectively. The films oriented in a particular direction showed superior electrical characteristics to the randomly oriented films.

Artificial dielectric superlattices of SrTiO3/BaTiO3(STO/BTO) and CaTiO3/BaTiO3 (CTO/BTO) have been formed by a pulsed laser ablation technique with an in situ monitoring of RHEED (reflection high energy electron diffraction) oscillation. The crystal structures can be controlled with atomic order accuracy and a large stress of 400–500 MPa is introduced at the interface between the BTO and STO layers. Xhe superlattices show higher dielectric constant than that of (Sr0.5Ba0.5)TiO3 films against the change of temperature or applied frequency. A large dielectric constant of 900 was observed for the superlattices with a stacking periodicity of 2 unit cells / 2 unit cells. Xhe superlattices show drastically different electrical behavior from that of the solid solution (Sr,Ba)XiO3 films, both with changing temperature and applied frequency. Broad maxima of the dielectric constants occur around 40–50 °C and the values remain large even for the temperature above 200 °C. On the contrary, in the case of CTO/BTO superlattices, lattice constants and dielectric constant do not change so much compared with STO/BTO cases. Lattice mismatch in the STO/BTO and the CTO/BTO superlattices are 2.5% and 5.5%, respectively. In the case of CTO/BTO, misfit dislocations such as stacking faults may occur at the interface between CTO and BTO layers owing to large lattice mismatch. Therefore, lattice strain is introduced effectively below the lattice mismatch of about 3%.

Ba0.44Sr0.56TiO3 (BST) thin films with various thicknesses were epitaxially grown on Pt/MgO(100) substrates with rf magnetron sputtering. The thickness dependence of lattice constant, D-E hysteresis and dielectric constant were evaluated for the BST films. The lattice constant in the thickness direction is elongated through the thickness range (33 to 221 nm), whereas the ferroelectric and the dielectric properties had strong thickness dependencies. The mechanism of the induced ferroelectricity is discussed in terms of the thickness dependence and deposition technique.

Epitaxial BaTiO3/SrRuO3 heterostructures were deposited on MgO and SrTiO3 substrates by 90° off-axis, rf-magnetron sputtering. A template layer growth was required to obtain epitaxy on MgO. The crystalline structure of the films was analyzed with x-ray diffraction. The leakage current and remanent polarization depended on the crystalline structure and processing parameters. The BaTiO3 thin films displayed remanent polarizations of 13 μC/cm2 and leakage current densities of 107 Amps/cm2 at 2 volts. The BaTiO3 thin films grown under optimal conditions displayed very little fatigue up to 5×108 cycles.

Films were deposited onto unheated, Ti/Pt coated Si substrates by reactive sputtering in an argon-oxygen atmosphere from a sintered PZT target, and subsequently crystallized at temperatures between 550 and 650 °C. Pt/PZT/Pt capacitors were formed by ion beam sputtering of top electrodes through a shadow mask. Electrical properties were found to depend on gas pressure during deposition. This effect is interpreted in terms of variations in film stoichiometry (particularly Pb content). Films with large excesses of Pb were found to exhibit high leakage currents and poor ferroelectric behavior, whereas films with lower excesses of Pb had low leakage currents, and good ferroelectric properties. Films with the largest Pb excess had a random orientation, while the film with the lowest Pb excess had a preferred (111) orientation. With 550 °C crystallization temperatures the films consist of a mixture of ferroelectric perovskite phase and either PZT pyrochlore or PbO. At higher crystallization temperatures no pyrochlore is detected.

Thin films of Pb(MgxNb1−x)Oz were produced by reactive sputtering from a lead target and columbite magnesium niobate powder targets at temperatures of 500–700°C on Pt/Ti/Si, Pt/SiO2/Si, MgO(lOO) and SrTiO3(100) substrates. The films in general deposited on Pt consisted of PbO and pyrochlore phases depending upon the deposition temperature. ICP analysis revealed that the films contained slightly less Mg than the target. This was attributed to negative ion preferential resputtering of the film within the discharge. However, films deposited at 650°C on MgO and SrTiO3 substrates from a lead target and magnesium niobate target which contained excess MgO, contained a highly oriented perovskite (100) Pb(Mg1/3Nb2/3)O3 [PMN] phase according to X-ray diffraction analysis. It was observed that the substrate composition and orientation greatly influenced the crystallinity of the deposited films.

Ferroelectric BaTiO3 thin films have been directly deposited on n-GaAs with carrier concentration of 5.3–8.2×1017/cm2. The BaTiO3 thin films with a thickness in the range of 80–120 nm were prepared by RF magnetron sputtering with a substrate temperature of 300°C. The as-deposited BaTiO3 films appeared to be amorphous with relative dielectric constants of around 15 and gave flat capacitance-voltage (C-V) curves, indicating poor interface properties and very high oxide charge density. After rapid thermal annealing (RTA) at 800°C for 60 sec, the relative dielectric constant of the BaTiO3 film increased to 82 and a sharp C-V curve was observed with oxide charge density of about 7×1012/cm2. However, the leakage current density increased from 4×10'11 A/cm2 for as-deposited BaTiO3 to 2×105 A/cm2 for RTA(800°C)-BaTiO3 at a field of 4×105 V/cm. By taking advantage of the best properties from both as-deposited amorphous BaTiO3 films (low leakage current density) and RTA(800°C)-BaTiO3 (high dielectric constant) the double layer structure was designed to enhance the electrical properties of the BaTiO3 films on GaAs. The most promising results in regards to the dielectric property and leakage current density are 76.5 and 9.7×109 A/cm2, respectively, for the double layer RTA(500°C)-BaTiO3 on RTA(800°C)-BaTiO3 structures.

Due to their high dielectric constant, good chemical stability and good insulating properties, lead zirconate titanate (PZT) thin films are considered as promising materials to replace Si3N4 and Ta2O5 for use as the capacitor dielectric in future high density DRAMs. Moreover, the ferroelectric quality of PZT films also allows use of this material in non volatile memories. In this paper, we investigate the properties of PZT films deposited from an oxide target of nominal composition {Pb1.1(Zr0.55,Ti0.45)O3} in a radio frequency (rf) magnetron sputtering system. The Pt(deposited at 450°C)/[TiN/Ti/BPSG/Si] structure annealed at 450°C at 10−6 mbar (Pt(450°C)/{TiN/Ti/BPSG/Si}450°c,10–6mbar) was used as a substrate material in this work. The PZT films were deposited at different pressures, and different substrate temperatures ranging from floating temperature to 400°C; the thicknesses of the sputtered films were in the 15–720 nm range. The kinetics of the sputtering process and the effect of sputtering parameters on film composition have been studied and related to the continuously monitored optical emission of the plasma. The relative cation and oxygen compositions of the films were determined by a new method based on the simultaneous use of Rutherford Backscattering Spectrometry (RBS) and Nuclear Reaction Analysis (NRA) induced by a deuteron beam. The conditions for the deposition of stoichiometric PZT thin films were established.

Electrical characterizations of the PZT films including resistivity, dielectric constant, dissipation factor were studied as a function of the temperature. From initial electrical measurements, it appears that a dielectric constant of 740 can be obtained for PZT 55/45 films deposited on a previously annealed Pt/TiN/Ti/BPSG/Si structure.

Surface and cross-section relief evolution of ferroelectric epitaxial (Ba,Sr)TiO3 films rf-sputtered on (001) HgO crystal cle-avage surface versus the oxygen worKing gas pressure P and subst-rate temperature T were studied. Specific features of both three-dimensional and two-dimensional epitaxy mechanisms corresponding to various deposition conditions were revealed. Difference between low and high P-T-value 3D epitaxy was established. The deposition of films with mirror-smooth surfaces and perfect interfaces is shown to be possible.

Preparation of ferroelectric lead zirconate titanate (PZT) thin film by electron beam evaporation of multicomponent oxides followed by a post-deposition synthesis of PZT films by step-annealing under O2 ambient is described. Incipient formation of Pb3O4-ZrO2-PbTiO3 solid solution by a 600°C annealing is required for crystallization of PZT phase. Two morphotropic phase boundary reactions between solid solution phase with TiO2 and PbTiO3 with ZrO2 are proposed for PZT growth. Polarization and capacitance-voltage hysteresis data are presented to establish ferroelectric behaviour.

The dielectric constant, loss tangent and Curie temperature for SrxBa(1−x)TiO3 (SBT) thin films with x = 0.2 – 0.8 have been investigated at microwave frequencies. SBT films (0.5 -3 μm thick) were grown on (100) MgO and LaAlO3 substrates by pulsed laser deposition at substrate temperatures from 850 – 900 °C in 0.35 Torr of oxygen. Deposited ferroelectric films were single phase, highly oriented, and characterized by x-ray rocking curve widths of < 0.5°. Highly oriented SBT films with x-ray rocking curve widths of 72 arc seconds were observed. In general, the thin film dielectric constant at microwave frequencies is low (200–950) compared to the reported bulk value, but strongly dependent on the Sr/Ba ratio. Biasing of a ferroelectric interdigital capacitor (< 200 kV/cm) produces a change in the dielectric constant which resulted in a phase shift in the reflected signal (S11) measured as a function of frequency from 100 MHz to 10 GHz. The dielectric loss tangent measurement, as measured at room temperature and 9.2 GHz, ranges from 0.1 to 1.2 × 10−3 and depends on the Sr/Ba ratio. These data show that SBT thin films are suitable for the development of frequency tunable microwave circuits and components.

Dielectric Ba1−xSrxTiO3 films were heteroepitaxially grown on Si (100) substrates by employing an epitaxial TiN interlayer. The crystallinity and surface morphology were investigated for the films prepared at various substrate temperatures and oxygen pressures. BaTiO3 and SrTiO3 films grown at 650°C and 550°C, respectively, at oxygen pressure of ∼105Torr had good crystallinity and very smooth surface morphology as observed by scanning electron microscopy and atomic force microscopy. Sharp interfaces with little interdiffusion of atoms were observed for these films by secondary ion mass spectrometry. Dielectric properties were evaluated for metal-insulator-metal capacitor structures, and revealed to be closely related to the crystallinity and surface morphology of films.

Optical multichannel emission spectroscopie studies and ICCD (intensified charge coupled device) imaging have been applied to real-time, in situ gas phase species identification and plume structure analysis during the pulsed excimer laser deposition (PLD) of various ferroelectric thin films. Additional information on the non-excited plume species has been obtained using molecular beam-sampling mass spectrometry. The materials studied included targets of PbZr0.53Ti0.47O3 (PZT) and BaTiO3. For the BaTiO3 films, the partial pressure of oxygen in the buffer gas and the atomic oxygen emission within the plume both correlated with the observed lattice parameter, as determined by X-ray analysis. Reduced plume oxygen content resulted in an increased lattice parameter that, in turn, could be related to a reduced oxygen content in the film. ICCD imaging of plumes from PZT targets identified the presence of ejected particulates in the plume after multiple laser shots had worked the target surface. Scanning electron microscopy (SEM) studies of the PZT target surface and film morphology, revealed cone-like formations on the target and éjecta on the films which correlated well with the ICCD observation of plume particulates.

We have formed thin films of ferroelectric and dielectric materials (BaTiO3, SrTiO3 and CaTiO3) by pulsed laser deposition on various kinds of substrates such as SrTiO3, LaAlO3 and MgO(100) single crystals. All the films can be formed epitaxially on the SrTiO3 substrate with c-axis orientation by choosing suitable conditions. The electrical behavior of these films such as dielectric constant and spontaneous polarization is quite similar to that of single crystals in bulk samples. The remanent polarization of BaTiO3 and PbTiO3 films are about 15 μC/cm2 and 80 μC/cm2, respectively. The value of 80 μC/cm2 is almost the same as that theoretically predicted and have not been obtain in the bulk samples. The unique advantage of the pulsed laser deposition technique is its ability to produce highly oriented stoichiometric films that show good electrical properties.

Ferroelectric multilayer capacitors (YBCO/BTO/YBCO) are fabricated on YSZ buffered Si (100) substrates by using pulsed-laser deposition technique. The deposition process is monitored in situ by using a Fourier Transform Infrared Spectrometer (FTIR), which measures the film's deposition rate and dielectric constant during the growth process. All four oxide layers in such a multilayer capacitor are grown in situ without breaking the vacuum, and without lowering the substrate temperature to below 600°C. The electrical properties and microstructures of the multilayer capacitor are studied and the optimal deposition condition are identified. Sharp resistive transitions are achieved for both the top and the bottom YBCO layers with on-sets at 90 K, zero resistance at 89 K for the bottom layer and 88K for the top layer. X-ray diffraction θ-2θand φ scans indicate that all four deposited oxide layers have their c-axis perpendicular to the substrate, and have less that 10% in-plane misorientation. The dielectric constant of the BTO layer is over 210. Hysteresis P-E characteristics and current-voltage curves are also measured to determine dielectric properties of the barium titanate films. Preliminary results with LaSrCoO (LSCO) electrode layer are also presented.

Ferroelectric thin films of barium strontium titanate (BSTO) have been deposited on bare and metallized substrates by pulsed laser ablation method under different oxygen ambients (150 mT and 50 mT). Under an oxygen pressure of 150 mT, the film composition was similar to that of its ablation target composition, viz. Ba0.4TiO3. However, when the films were deposited under the lower oxygen pressure, x-ray diffraction studies showed the presence of a secondary phase. The electrical characteristics of the films were measured to examine the effect of the stoichiometry on the dielectric constant and tunability. The results of this study will be presented.