We have analyzed the leakage behavior of polycrystalline MOCVD (Ba,Sr)TiO3 thin films as a function of both temperature and field. Of the possible mechanisms, thermionic (Schottky) emission gives a self-consistent description of the temperature and field dependencies of the true leakage current for fields in the range of 240–970 kV/cm, and yields realistic barrier heights of 1.2 eV for Pt as the cathode material. For film thicknesses of interest for use in DRAMs, the capacitance-voltage characteristics are explained via Landau-Ginzburg-Devonshire theory. Preliminary resistance degradation studies are also discussed.

Pb(Zr,Ti)O3 (PZT) films with very thin PbTiO3 (PT) buffer layers inserted between the film and the Si/SiO2/Ti/Pt substrate were grown by a rf magnetron sputtering technique. The Xray diffraction patterns and the surface morphology of PT as a function of the thickness, in the range of 20 to 400 Å, were first investigated. Such a marked contrast in morphological features was not observed when the thickness was above 400 Å. The films were grown in-situ at 500°C. We found modification of the PT orientation when its thickness varied between 20 Å and 400 Å. This implies a gradual evolution of the lattice parameters in the nucleation stage of PT films. Insertion of these buffer layers was found to exert marked effects. Up to 400 Å the PT was grown with a [100] preferred orientation. The orientation of PZT could be controlled by changing the thickness and then the orientation of PT. The results will be discussed in terms of the effects of the buffer layer on the crystalline structure and the surface morphology of PZ

PZT thin films with the composition Pb(Zr0.6Ti0 4)O3 were processed via metallo-organic decomposition (MOD) with {111} and {100} orientations. Ferroelectric measurements showed that the {111} and {100} oriented films had remanent polarizations of 19.5 μC/cm2 and 16 μC/cm2, respectively. Both x-ray pole figure analysis and the Harris texture index were used to quantify the degree of {100}, {110}, and {111} orientation in each film, with reasonable agreement between the two methods. The {100} oriented thin film was determined to be 582 times random for the Harris technique versus 522 times random for pole figure analysis, while the {111} oriented film was 41 times random for the Harris technique and 81 times random for pole figure analysis. The axisymmetric texture of the films allow 2-D pole figure analysis to provide a quantitative characterization of film texture.

Thin-film decoupling capacitors based on ferroelectric (Pb,La)(Zr,Ti)O3 films are being developed for use in advanced packaging applications. The increased integration that can be achieved by replacing surface-mount capacitors should lead to decreased package volume and improved high-speed performance. For this application, chemical solution deposition is an appropriate fabrication technique since it is a low-cost, high-throughput process. The use of relatively thick Pt electrodes (˜1 μm) to minimize series resistance and inductance is a unique aspect to fabricating these devices. In addition, the important electrical properties are discussed, with particular emphasis on lifetime measurements, which suggest that resistance degradation will not be a severe limitation on device performance. Finally, some of the work being done to develop methods of integrating these thin-film capacitors with ICs and MCMs is presented.

In this study, the use of a fiber optic technique for the measurement of the piezoelectric properties of ferroelectric bulk and thin film samples was investigated. The strain and piezoelectric properties (namely the d33 coefficients) were measured using the MTI-2000 Fotonic Sensor, which uses the principle of the optical lever to resolve very small changes in sample displacement (1 Å). Using this technique, we were able to detect the very small strains associated with the converse piezoelectric effect for PVDF films and bulk PZT samples, and correlate the results with data acquired from direct piezoelectric effect measurement. Comparison of the data sets prove that the optical lever would be a useful optical technique for measuring of the d33 values of ceramic thin films, such as BaTiO3, ZnO, and PZT.

Lanthanum-doped lead zirconate titanate (PLZT) films, with thickness up to 10 μm, are fabricated on platinized silicon substrates through a modified sol-gel technique. Thicknessdependent piezoelectric properties measured with a double-beam laser interferometer show piezoelectric relaxation in field-induced strain as the ac driving field exceeds 10 kV/cm. In addition, the strain levels of PLZT thick films are approximately one third of those of undoped PZT films under the same fabrication and measurement conditions. For 1 μm PZT(55/45) films doped with 0, 2, and 4 mole% La, the P-E hysteresis exhibits decreasing squareness with increasing lanthanum content while the piezoelectric d33 coefficient reduces from 130 to 52 pC/N. Residual (tensile) stress in these films and resulted depoling effect may be responsible for this phenomenon.

Ferroelectric Pb1−xLaxTiO3 (PLT, x = 0.00 ˜ 0.28) thin films have been prepared on MgO(001) substrates using pulsed laser deposition. The degree of c-axis orientation in PLT films increased as the La concentration (x) increased with systematic changes in lattice constants and transformation strains. For x ≥ 12, the PLT films showed full c-axis orientation.

In order to understand why the domain evolution in PLT films changes with the La concentration, we have conducted high temperature X-ray diffraction to simulate the cooling process during which the domain structure is evolved. Lattice constants, degree of c-axis orientation, crystal quality of PLT films were characterized as a function of temperature. Lattice constants along substrate normal direction showed similar characteristics with those of powder. The degree of c-axis orientation just after the phase transformation at the Curie temperature also increased with La concentration. The crystal quality, which is quantified by the line width of diffraction peak, is insensitive to La concentration in paraelectric phase. However, it shows significant variation after the domain structure is evolved.

The study of ferroelectric thin films has evoked special interest owing to their numerous applications. In this study, epitaxial or highly oriented PbTiO3/PLT (Lead Titanate / La modified Lead Titanate) ferroelectric superlattice thin films were grown by the metalorganic chemical vapor deposition (MOCVD) technique. Compositional modulation by Secondary Ion Mass Spectroscopy (SIMS) established the nature of these films as desirable for high quality device applications. The thickness and the refractive index of each film was determined by using a prism coupler. The dielectric behavior of these films was studied as a function of frequency.

The phase diagram of eptaxial BaTiO3 films in the coordinates of T and αs ( substrate thermal expansion coefficient) is constructed on the basis of the thermodynamic analysis which has been carried out earlier [1]. It is found that two new phase are formed under bi-axial stress. The temperature dependencies of polarization and unit cell parameters for the films on the KTaO3 and SrTiO3 substrates are also calculated.

This paper presents the in situ investigation of the crystallite evolution/growth during annealing of amorphous sol-gel Pb(Zr,Ti)O3 thin films by elastic light scattering. XRD and SEM measurements of partly crystallized films of crystallite evolution were used for verifying the method.

Lead zirconate titanate, Pb(Zr0.53Ti0.47)O3 (PZT), coatings were prepared using a metallorganic decomposition (MOD) route with lead and titanium acetates and zirconium acetylacetonate in acetic acid and water. Films with thickness of 0.66 μm were prepared on (100) Si with a layered bottom electrode (Pt/Ti/TiO2/SiO2). Dielectric constant and loss were 1100 and 0.04 (1 kHz), respectively, and remnant polarization and coercive field were 30 μC/cm2 and 40 kV/cm. Piezoelectric coefficient (d33) of the PZT film, measured with a singlebeam laser interferometer, was 41 pm/V. Standard micromachining techniques were used to etch the PZT to form discrete PZT posts for preparation of the ceramic phase for composite coatings with a 1–3 connectivity. SEM was used to determine the dense and etched film microstructure. Preliminary ion milling results, used to etch the PZT, are also presented.

Ferroelectric thin films typically differ from bulk ceramics in terms of both the average grain size and the degree of stress imposed on the film by the substrate. Studies on bulk ceramics have demonstrated that the number of domain variants within grains depends on the grain size for sizes <˜lμm. This can diminish the poling efficiency of the material. Since most thin films show primary grain sizes well below a micron, similar effects should be observed in films. In addition, since the perovskite ferroelectrics contain ferroelastic as well as ferroelectric domains, it seems clear that stress in thin films may markedly alter the degree to which domain walls contribute to the observed properties. In this paper, the relative importance of these factors are discussed for several types of ferroelectric thin films. Films have been prepared by pulsed laser deposition, magnetron sputtering, and by sol-gel processing. It has been found that epitaxial BaTiO3 films are ferroelectric at 77K down to thicknesses as low as ˜ 60nm. Data on the low and high field electrical properties are reported as a function of temperature, the film crystallinity, and film thickness for representative perovskite films.

High-quality La-modified PbTiO3 (Pb1−xLaxTi1−x/4O3; PLT) thin films were prepared by an rf-magnetron sputtering method. In this method, intermittent deposition was realized by periodical repetition of deposition and nondeposition processes. This deposition was found to enhance the horizontal grain growth of the films. The PLT thin films exhibit the phenomena named “self-polarization” and have high pyroelectric properties (pyroelectric coefficient γ of 5.0×10−8C/cm2K and low dielectric constant εr of 185) without a poling treatment. It was interestingly found that this self-polarization of the PLT thin films depends on the substrate temperature (Ts) and is based on a fairly small difference of the film composition (Pb/Ti). The pyroelectric properties were improved by means of addition of Mg to the PLT thin films. These thin films are expected to offer suitable materials for pyroelectric infrared (IR) sensors. High sensitive pyroelectric IR sensors (single element type and linear array type) were fabricated by using the PLT (x=0. 1) thin films with the new structures and the device processes. The sensors have remarkably high specific detectivity D* of 3.5×108 cm. Hz1/2/W and very fast response. A new compact IR sensing system using the linear array sensor (8 elements) has been developed for a new type of room air-conditioner.

Thin films of lanthanum-doped lead titanate for use in pyroelectric detectors were deposited on Si wafer system substrates by an RF magnetron sputtering method. Deposition was from a ceramic target with excess lead using Ar plus N2O sputter gases. The film structure, composition and electrical properties were examined as a function of substrate temperature during film deposition, Tsub, from 600°C to 750°C. Dense, featureless film cross-sections existed up to Tsub=625°C, while vertical columns, indicative of crystalline material, were present from Tsub=650°C upwards. At Tsub=600°C films were amorphous, but from Tsub=625°C upwards a highly crystalline perovskite phase was found. The tetragonality was very small, c/a˜1.006, indicating the existence of a pseudo-cubic structure. Compared to the idealized chemical formula, Pb1−xLaxTi1−x/4O3, films produced at Tsub<650°C or Tsub>700°C were Pb deficient, while only in the very narrow 650–700°C Tsub range was near-stoichiometry obtained, with a slight lack of Ti. The substrate temperature during deposition is apparently a critical factor in obtaining stoichiometric films. The La content with respect to Pb was 9.5% which would be expected to yield a reasonably tetragonal crystal structure in bulk material, however stress due to the substrate may account for this discrepancy. The relative permittivity, εr, showed a sharp transition from ˜50 at Tsub=600°C to 450–550 between 650°C and 750°C. This behaviour parallels both the microstructural and crystal lattice changes from amorphous to perovskite material. Even though on polycrystalline underlayers, pyroelectric activity, p, was measured on as-deposited films, the polarization being directed into the substrate and a peak of 1.2×10−4Cm−2K−1 appearing at Tsub=700°C. After DC thermal poling, at 100°C with 8V for 20min, p increased dramatically, with Tsub 700°C and 725°C films exhibiting p=2.0×10−4Cm−2K−1. The peak in the poled p value corresponded to the maximum found in the crystal tetragonality and agrees with increasing p as polarization increases from a cubic to tetragonal structure.

Solid phase epitaxial growth of LiNbO3 thin films, using a methoxyethoxide solution process, has been examined for optical waveguide applications. The growth variables such as crystallization temperature, crystallization time, and film thickness have been found to be critical factors in the quality of LiNbO3 thin films. High quality epitaxial LiNbO3 films were grown on sapphire (001) substrates using optimized buffer layers. The LiNbO3 showed single orientation, rocking curve full width at half maximum less than 0.04°, and rms roughness of 2.3 nm, in addition to refractive index of 2.24 and optical propagation loss of 3.0 dB/cm.

A mixed alkoxide liquid precursor was used to form epitaxial ferroelectric potassium niobate, KNbO3, thin films through the sol-gel technique by carefully designing the solution chemistry and reaction processes. The double alkoxide solution was prepared through hydrolysis and condensation reactions between different metal alkoxides in solution. Fabrication of heteroepitaxial single crystal thin films of KNbO3 deposited on single crystal substrates of MgO and SrTiO3 will be described. Film structure was investigated with X-ray and electron diffraction, and transmission electron microscopy. Second harmonic generation of 1064 nm incident light was demonstrated for KNbO3 thin films in a waveguide configuration. Transient photorefractive gratings in Fe-doped KNbO3 were studied by a two-beam coupling technique for various writing intensities and wavelengths.

Thin films were deposited by radio frequency (rf) magnetron sputtering on Pt/TiN/Ti/SiO2/Si substrates starting from a ceramic Pb(Zr0.4Ti0.6)O3 or metallic Pb1.1(Zr0.4Ti0.6) target. To promote the ferroelectric properties, films were successively processed by rapid thermal annealing (RTA). Before and after the RTA process, the film optical constants, in terms of refractive index and. extinction coefficient, were measured by spectroscopic ellipsometry and spectrophotometry and their values were related to the film composition determined by nuclear microanalysis with a precision better than ±2%. By adjusting the sputtering conditions, it was possible to grow different films with oxygen stoichiometry (O/Pb) in the range of 2.5-4.5. The electrical P-E characterization revealed a strong relation between the optical properties (film composition) before annealing and the hysteresis loop after annealing. This was mainly attributed to changes in the film oxidation during RTA and indicates that ferroelectric properties can be optimized adjusting the O/Pb ratio in the film.

We have studied the pyroelectric properties of the PLT(10) thin film deposited on a p-doped poly-Si electrode by using the sol-gel method. Measurement of the dielectric constant as a function of temperature shows the typical characteristics of a ferroelectric. The dielectric constant reaches a maximum at 295°C, which can be thought of as the Curie temperature. The PLT(10) thin film on p-doped poly-Si fabricated in this research shows excellent pyroelectric properties. The pyroelectric coefficient and the fiqures of merit, Fv and FD at room temperature are measured as 5.76 × 10−8 C/cm2 °C, 1.17 × 10−10C-cm/J and 0.93 × 10−8C-cm/J, respectively.

The fabrication methods of ferroelectric (FE) thin films have received special attention in recent years because of the needs of FE thin films integrated with semiconductor devices. Rapid thermal processing (RTP) has developed in fabrication of FE thin films because it can reduce processing temperature and time duration, and it also improves the properties of FE thin films compatible with semiconductor devices. The thin film samples used were prepared by a multi-ion-beam reactive cosputtering system (MIBRECS) at room temperature. The samples were then subjected to a post-deposition annealing in a RTP system. It was found that PbTiO3 (PT) thin film could grow on amorphous or polycrystal interfacial layer and the PT thin films annealed by RTP showed the prefered [110] and [100] textures. The effect of interfacial layer on the crystallization and microstructure of the films was also discussed.

Photoelectric properties of PbTiO3/Si heterostructures were investigated over a broad range of wavelengths. The spectral distribution of the a.c. open-circuit voltage was measured for wavelengths ranging from 0.35 μm to 4 μm. Two local peaks are observed at 0.38 μm and 0.9 μm which can be attributed to band-to-band excitations in PbTiO3 and Si respectively. The shape of the a.c. signal depends both on the light intensity and on the wavelength. When the heterojunction is reverse-biased, a d.c. photocurrent was observed which has a similar spectral distribution as the a.c. open-circuit voltage.