Bi-layered ferroelectric strontium bismuth tantalate (SBT) thin films of various film compositions were deposited on Pt/Ti/SiO2/Si substrates by metalorganic chemical vapor deposition (MOCVD) and crystallized at 700°C in oxygen ambient. Phase transition, orientation, second phases and remanent polarization were investigated with respect to film stoichiometry. X-ray diffraction (XRD) measurements revealed that excess Bi lowers the transition temperature from fluorite-type to ferroelectric phase. However, SBT films with Bi-excess of 15% or higher exhibit pronounced Bi-loss during crystallization and a decrease in the relative intensity of the (200) peak. Highly Sr-deficient films are not fully crystallized but support pyrochlore formation. The maximum remanent polarization is obtained at a Sr-deficiency of 15–25% and a Bi-excess of 10% (0.85/2.20/2.00).

The effects of reactive ion etching damage on the electrical properties of Pt/SBT/Pt capacitors have been investigated. The plasma treated SBT/Pt layers showed a significant decrease in remanent polarization compared with that of the reference sample. The remanent polarization of the plasma treated layers varied with the gas ratios of the Cl2/Ar plasma. XPS analysis of the plasma treated SBT/Pt samples showed that the surface composition was significantly changed as the gas ratios were varied, which resulted in a polarization decrease in the plasma treated samples. Plasma treatment also caused a voltage shift of the hysteresis loops along the voltage axis. The magnitude of the voltage shift was increased for the chlorine-rich plasma. The results of surface analysis revealed that the voltage shift is caused by oxygen deficiency at the SBT surface. Based on our experimental results, reactive ion etching damage was explained in terms of physical and electrical effects of the plasma on the electrical properties of the ferroelectric Pt/SBT/Pt capacitors.

We have observed the growth of domains in ferroelectric barium titanate and potassium niobate using a transmission electron microscope. When domains move in response to electric fields we see a scaling effect where the fine scale domain structure is activated first, followed by larger length-scale patterns. Curvature and tilting of domain walls leads to local uncompensated displacement charge and external fields can interact with these charged walls. In this paper, we posit that the presence of displacement charge on domain walls is important for polarization switching. Charge-neutral domain configurations are in a lower energy state and are harder to switch. We argue that the number of charge-neutral, low energy domain configurations can increase with time. This mechanism provides an intrinsic contribution to ferroelectric fatigue.

CaBi2Ta2O9 and BaBi2Ta2O9 thin films were successfully prepared by using triple alkoxide precursors such as Ca[BiTa(OC2H5)9]2 and Ba[BiTa(OC2H5)9]2, respectively. As-deposited films were amorphous and crystallized below 500°C by rapid thermal annealing in oxygen. The crystallinity improved with annealing temperature. The development of the crystal structure and surface topography of the thin films were investigated. Additionally, some electrical properties were evaluated.

Thin films of ferroelectric (SrBi2Ta2O9)x(Bi3TiNbO9)1-x layered structure (for x = 0.0, 0.2, … 1.0) were prepared by a metal organic solution deposition method on Pt/TiO2/SiO2/Si substrates. Raman spectroscopy, X-ray diffraction, atomic force microscopy (AFM), and electrical characterization techniques were utilized to study the inclusion of SrBi2Ta2O9 (SBT) in the Bi3TiNbO9 (BTN) system. The Raman spectra show frequency shifts and broadening of modes as x increases from 0.0 to 0.4, which are related to the nature of Sr and Bi in the A-sites, and Ta, Ti, and Nb in the B-sites. Smooth surfaces without any cracks or defects were evidenced in each of these films by AFM. These images also indicate that the grain size in the films increases with increasing SBT content in the BTN compound. Electrical measurements show that the remanent polarization (Pr) and the coercive field (Ec) values in the x=0.0 film (2 μC/cm2 and 30 kV/cm, respectively) increase to 12.5 μC/cm2 and 125 kV/cm for x=0.6. A decrease in these parameters was found for higher compositions.

A new chemical solution for the deposition of SrBi2Ta2O9 (SBT) thin films using crown ether is proposed. Crown ether enhances the solubility of bismuth acetate in acetic acid, which makes a solvent solution possible. A metal acetate-based SBT precursor solution was prepared in acetic acid using 18-crown-6, strontium acetate, bismuth acetate and tantalum ethoxide. (115)-preferentially oriented ferroelectric SBT thin films were formed on Pt/TiO2/SiO2/Si substrates by spin-coating with the new solution. After post-annealing at 800°C, a hysteresis loop obtained from a 2000Å thick SBT film with Pt electrodes showed a remanent polarization of ∼3μC/cm2 and a coercive voltage of ∼50kV/cm. It was shown from SIMS depth profiles that excess bismuth atoms in the SBT thin film diffused towards the Pt electrodes during post-annealing.

Preferentially (151)-oriented Sr2(Ta1-x, Nbx)2O7 (STN) thin films on Pt have been prepared at temperatures as low as 550 and 600°C, in O2 and N2O atmospheres, respectively, by pulsed laser deposition (PLD). The temperatures are significantly lower than those prepared by sol-gel methods, where 950°C was reported. These are the lowest growth temperatures of crystalline STN thin films. Composition ratio (x) in the target material was determined to be around 0.3 from measurement of the Curie temperature and ferroelectric properties. Active oxygen generated by laser irradiation in ambient O2 or N2O atmosphere is found to be very effective for chemical reaction, and decreases the growth temperature of crystalline STN films. It is also confirmed by surface AFM and cross-sectional SEM observations that the film has a columnar-shaped structure with grain size ranging from 50 to 100 nm. Remanent polarization (Pr) and coercive field (Ec) are 0.4μ C/cm2 and 30 kV/cm, respectively. Finally, we expect the low temperature STN film prepared by PLD to be a promising ferroelectric for the application in ferroelectric memory FETs.

The effect of growth conditions such as substrate temperature and oxygen partial pressure on the microstructure and properties of pulsed laser deposited SBTN thin films on Si(100) and MgO(100) substrates have been studied. Crystallization of films begins at room temperature but, the obtained phase was non-ferroelectric. The influence of oxygen pressure (150 to 450 mTorr) on crystallinity of the films deposited on Si(100) at 750°C is negligible. XPS studies of as-deposited films reveal that the oxygen vacancies are preferably present near the Bi ions at the Bi2O2 layers and vary with substrate temperature and oxygen partial pressure. Also, XPS studies of Sr 3d core level for SBTN films suggest that the oxygen ions in the Sr(Ta/Nb)2O7 perovskite layers are much more stable than those in the Bi2O2 layers. Micro-Raman studies of SBTN films deposited below 700°C show Raman modes of a non -ferroelectric phase.

Three kinds of oriented electrodes of Pt, Ir and Pt/Ir electrodes were prepared using electron beam evaporation techniques for deposition of PZT thin films. An oxide MOCVD reactor with liquid delivery system was used for the growth of PZT thin films. [Pb(thd)2], Zr(TMHD)4 and Ti(IPO)4 were dissolved in a mixed solvent of tetrahydrofuran or butyl ether, isopropanol and tetraglyme to form a precursor source. The deposition temperature and pressure were 500 - 650°C and 5 - 10 Torr, respectively. The experimental results showed PZT thin film deposited on various electrodes had different phase formation, microstructure and ferroelectric property. The X-ray patterns showed the perovskite phase of PZT was formed on both Ir and Pt/Ir electrodes at 550°C. The grain size of the PZT thin film increases after a further, higher temperature annealing. The as-deposited PZT thin film on Pt electrode exhibits pyrochlore phase at 550°C. The phase is transformed to perovskite phase after 650°C annealing. The experimental results also indicated that the MOCVD PZT thin film on Pt/Ir exhibits better ferroelectric and electrical properties compared to those deposited on Pt and Ir electrodes. A 300 nm thick PZT thin film on Pt/Ir electrode has a square, well saturated, and symmetrical hysteresis loop with 2Pr value of 40 μC/cm2 and 2Ec of 73 kV/cm at an applied voltage of 5 V. The hysteresis loop of the PZT thin film is almost saturated at 2 V. The leakage current of the film is 6.16 × 10−7 A/cm2 at 100 KV/cm. The electrode effects on ferroelectric properties of PZT thin films also have been investigated.

A large set of films with textures ranging from almost fully random to highly {111} textured were generated using an ULVAC ZX-1000 production sputter deposition machine. The PZT texture was altered by changing the {111} texture of the underlying Pt electrode, but the PZT thickness, composition, sputter deposition conditions, and crystallization anneals were held constant for all samples. X-ray diffraction peak intensities were used to calculate the volume fraction of {111}, {100}, and randomly oriented material composing the PZT films. All samples contained less than a 6% {100} textured volume fraction. It was found that the switchable polarization is linearly dependent on the {111} textured volume fraction. The voltage required to achieve 90% saturation of the switchable polarization also has a linear dependence on the {111} textured volume fraction. The rate of fatigue and degradation of the switchable polarization caused by same-state and opposite-state retention tests were independent of the {111} textured volume fraction.

Lanthanum doped lead zirconate titanate (PZT) thin films have been prepared on Pt/IrO2/Ir/SiO2/Si substrates to improve the ferroelectric and retention properties. The microstructure and electrical properties of the PZT capacitors were evaluated as a function of La content. The crystalline orientation was appreciably influenced by the addition of La in PZT thin films. The microstructures of films containing 0 and 0.5 mol% La were single phase perovskite, but for La = 1 mol%, a second phase was detected by SEM observation. The 0.5 mol% La doped PZT thin film capacitor showed the best ferroelectric and retention properties for ferroelectric random access memory compared to non-doped PZT.

Selective nucleation and lateral growing method have been developed for high quality ferroelectric PZT(65/35) thin films using perovskite-phase PZT island seed. The PZT films on PZT seed island were transformed into the perovskite phase at temperatures as low as 540°C, which is 150°C lower than compared to that of PZT thin films deposited on Pt films. The temperature difference enables lateral growth without undesirable random nucleation. Maximum grain sizes of the perovskite-phase PZT films were determined by the annealing temperature. The PZT thin films show a leakage current density of 8×10−8 A/cm2, breakdown field of 1240 kV/cm, saturation polarization of 42 μC/cm2, and remanent polarization of 30 μC/cm2, whose values were maintained up to 2×1011 cycles. In this study, we show that when there was no grain boundary in the area measured, degradation such as fatigue and retention was not observed even with Pt electrodes. So the main source of degradation is the grain boundary in the PZT thin films.

Al substitution for Zr/Ti site of PZT was attempted using a sol-gel method, and the ferroelectric properties of 200nm-thick Al doped PZT thin films were compared with those of non- doped PZT film. The leakage current of the thin films decreased with increasing Al content. Ps and Pr also decreased with increasing Al content, whereas Ec did not show a significant change. Furthermore, a simple capacitor cell structure like FeRAM was prepared using a seed layer process. The capacitor structure was Pb(Ti0.975Al0.025)O3/ Pb1.1((Zr0.52Ti0.48)0. 975Al0.025)O3/ Pb(Ti0.975Al0.025)O3, and 2Pr was 26μC/cm2. The fatigue properties of the A1 doped PZT capacitor cell showed a little improvement, because the reduction rate of the fatigue was smaller than that of non-doped PZT thin film.

Lead zirconate titanate (PZT) thin films were fabricated by a three-step heat-treatment process which involves the addition of -10, 0 and 10 mol% excess Pb to the starting solution and spin coating onto Pt/Ti/SiO2/Si substrates. Crystalline phases as well as preferred orientations in PZT films were investigated by X-ray diffraction analysis (XRD). The microstructure and composition of the films were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron probe microanalysis (EPMA), respectively. The well-crystallized perovskite phase and the (100) preferred orientation were obtained by adding 10% excess Pb to the starting solution. It was found that PZT films to which 10% excess Pb was added had better electric properties. The remanent polarization and the coercive field of this film were 34.8 μC/cm2 and 41.7 kV/cm, while the dielectric constant and loss values measured at 1 kHz were approximately 1600 and 0.04, respectively. Dielectric and ferroelectric properties were correlated to the microstructure of the films.

We have investigated the structural and electrical properties of Sr-modified Pb(Zr,Ti)O3, i.e., (Pb1-xSrx)(Zr0.53Ti0.47)O3 (PSZT), thin films. Sol-gel derived PSZT films were deposited by spin casting onto Pt/Ti/SiO2/Si substrates. Ferroelectric perovskite phases were found for all specimens (x ≤ 0.6), which implied the successful substitution of Sr for Pb. The values of dielectric constant (εr) as well as remanent polarization (Pr) of PSZT capacitors decreases monotonically with increasing Sr for x ≥ 0.1. PSZT (x=0.4) thin film was found to be applicable to high permittivity films for high density dynamic random access memories, whose Pr and εr are 5 μC/cm2 and 350, respectively, and leakage current density is low as 1×10−7 A/cm2 at a electric field of 100 kV/cm. In this paper, we also discuss the characteristics of Sr-modified PbTiO3 thin films.

Ferroelectric Pb(Zr0.53Ti0.47)O3 (PZT) thin films with preferred orientations were successfully deposited on the Pt/Ti/SiO2/Si wafer at low temperature of 525°C by the chemical solution deposition from molecular-designed precusor solution with 20 mol % excess lead than a stoichiometric composition. The composition of the resultant PZT thin films showed slightly lead excess than a stoichiometric composition. In addition, orientation of the resultant PZT thin films could be controlled by changing the pre-annealing temperature or insertion of thin PbO layer, which affected the interfacial state between Pt electrode and PZT thin films. The electrical properties of the resultant PZT thin films were also affected by the orientation of the resultant films. As a result, orientation of the low-temperature processed PZT thin films had large effect on the electrical properties of the resultant films.

90nm-thick PZT capacitors using Pt/thinSRO stacked electrodes showed 2V operation capability, no remanence degradation after more than 1E10 switching cycles, and low imprint. Effects of SRO(SrRuO3) electrode have been studied for high-endurance PZT capacitors. In capacitors with only top SRO electrodes, the SRO increased polarization and improved saturation property compared to Pt electrode PZTs. Fatigue and imprint degradation was caused by Pt bottom electrode interface deterioration. It is thought that the oxygen vacancies created with Pb vacancies are important respecting endurance and retention. PZT films crystallized on SRO showed smaller coercive voltage Vc (2/3 of that for PZT/Pt) with random orientation. The SRO layers block Pb diffusion and supply oxygen, thereby resulting in less oxygen vacancy accumulation at PZT interfaces. We have improved the imprint property by the reduction of thermal budget in SRO/PZT/SRO structures.

The microstructure and electrical properties of lead zirconate titanate Pb(Zr,Ti)O3 (PZT) films prepared by chemical solution deposition (CSD) with and without lead titanate (PT) seed layers were examined as a function of Ir/lr oxide electrode type. The novel PZT CSD solution was prepared from a mixture of zirconium and titanium butoxyethoxides and lead ethylhexanoate dissolved in butoxyethanol. The use of excess-lead (PbxsTi) and stoichiometric PT seed layers was found to promote PZT(111) orientation on Ir but not on Ir oxide. Ir substrate thickness was observed to influence orientation of PZT deposited on stoichiometric PT with greater PZT(111) texturing on thinner Ir(111) substrates. PZT with greater PZT(111) texturing tended to have greater remanent polarization (2Pr, μC/cm2). PZT deposited on stoichiometric PT seed layers on Ir(111) was of higher film quality than PZT deposited on PbxsTi seed layers on Ir(111). The PZT films deposited on stoichiometric PT on Ir(111) had enhanced PZT(111) orientation, a reduced pyrochlore content, and tended to saturate at lower coercive fields, have higher remanent polarization, squarer hysteresis loops with less tilt and greater fatigue endurance. The use of iridium oxide top electrode was demonstrated to significantly improve fatigue endurance compared to use of an iridium top electrode.

Epitaxial Pb(Zr,Ti)O3 (PZT) thin films with various thicknesses ranging from 40 to 400nm were prepared on SrRuO3/SrTiO3 by metalorganic chemical vapor deposition (MOCVD). The dependence of lattice constant on the film thickness and temperature was examined. The PZT films obtained showed ferroelectric hysteresis loops even when film thickness was 40nm. Applied voltage for obtaining high polarization density decreased as film thickness decreased. The 40nm-thick PZT film had the polarization density (Pr) of 38mC/cm2 at an applied voltage (Vc) of 0.7V.

Electrode stability, interdiffusion, phase purity and deviation from stoichiometry at the PZT-electrode interface are key issues in PZT thin film integration. This article highlights the use of transmission electron imaging combined with energy dispersive spectroscopy (EDS) for the investigation of these phenomena. The accuracy of the EDS analysis is discussed. It will be shown that using a standard PZT sample and controlled conditions, reliable analysis can be performed.

Diffusion mechanisms have been studied for Pt based electrode systems and RuO2-based electrode systems developed for direct integration onto silicon. The materials studied were composed of stacks of silicon-silicon oxide, an adhesion layer (Ti, Ta or TiOx), an electrode (Pt or RuG2) and PZT (45/55). The PZT was deposited by sol gel using the same parameters to allow for comparison of the different electrodes. Four different electrode / adhesion layer materials were compared (Pt/Ti, Pt/TiOx, Pt/Ta and RuO2 / TiO2). In the case of Pt, lead and oxygen diffusion through the electrode is observed. While the initial Ta layer transforms into a homogeneous pyrochlore phase, the Ti adhesion layer is heavily deformed. In the case of TiOx the lead is mainly incorporated at the interfaces with Pt and with SiO2. No lead diffusion to the adhesion layer is observed for the RuO2 electrode. In-situ sputtering and sol-gel deposition of PZT are also compared. The sol-gel films are close to the right stoichiometry for the perovskite while the sputtered films contained an excess of lead. No sign of second phase is found by X-ray diffraction (XRD), by EDS and by high resolution transmission electron microscopy (HRTEM) which suggests that the excess lead is accommodated in the perovskite lattice.