Pb(Zr0.52Ti0.48)O3 (PZT) thin films were coated onto Pt/Ti/SiO2/Si substrates by a sol-gel method and then crystallized by
2.45 GHz microwave irradiation in the magnetic field. The crystalline phases and microstructures as well as the electrical
properties of the PZT films were investigated as a function of the annealing temperature from 550 to 750°C for 60 s. The
crystallization behavior of the PZT films annealed at 650°C for different times were also investigated. X-ray diffraction
and transmission electron microscopy reveal that the pyrochlore phase is formed initially but that it transforms into the
perovskite phase very quickly. The ferroelectric and dielectric properties of the PZT films are correlated to the
crystallization behavior. The annealing time to obtain perovskite PZT films with good electrical properties at 650°C is
only 60 s, and is much shorter than that in conventional furnace annealing process. The reasons for the reduction of
annealing time in the rapid microwave annealing process are also discussed.
The effect of microwave irradiation process on crystallization of Pb(ZrxTi1-x)O3 (PZT) films was investigated. The PZT
thin films were coated on Pt/Ti/SiO2/Si substrates by a sol-gel method and then crystallized by single-mode 2.45 GHz
microwave irradiation in the magnetic field at 500°C for 30 min and 650°C for 60 s, respectively. The crystalline phases,
microstructures and electrical properties of the PZT films are investigated. X-ray diffraction analysis indicated that both
the films heated by microwave irradiation at 500°C for 30 min and those at 650°C for 60 s were crystallized well into the
perovskite phase. However, the PZT films crystallized at 500°C for 30 min had a (100)-preferred orientation while the
PZT films crystallized at 650°C for 60 s had a (111)-preferred orientation. The average values of remanent polarization,
coercive field, dielectric constant and loss of the PZT films crystallized at 500°C for 30 min are approximately 21
μC/cm2, 90 kV/cm, 510 and 0.07 respectively, whereas the PZT films crystallized at 650°C for 60 s are approximately 27
μC/cm2, 82 kV/cm, 900 and 0.05 respectively. The difference between the electrical properties of the PZT films
crystallized by deferent process can be related to the microstructure effect.
The effect of microwave heating with a frequency of 2.45 GHz on the low-temperature crystallization of Pb(ZrxTi1-x)O3
(PZT) films was investigated. PZT thin films were coated on Pt/Ti/SiO2/Si substrates by the sol-gel method and then
crystallized by single-mode 2.45 GHz microwave irradiation in the magnetic field. The elevated temperature generated
by microwave heating used to obtain the perovskite phase was only 450°C, which is significantly lower than that of
conventional thermal processing. The PZT films crystallized by microwave heating at 450°C showed similar
ferroelectric properties to those of the films crystallized by conventional thermal processing at 600°C. The average
remanent polarization and coercive field of the PZT films are approximately 21 µC/cm2 and 90 kV/cm, respectively. It is
clear that single-mode microwave irradiation in the magnetic field is effective for obtaining perovskite PZT thin films at
low temperatures.
Pb(ZrxTi1-x)O3 (PZT) thin films were coated on Pt/Ti/SiO2/Si substrates by a sol-gel method and then crystallized by
28 GHz microwave irradiation. The crystalline phases and microstructures as well as the electrical properties of the
microwave-irradiated PZT films were investigated as a function of the elevated temperature generated by microwave
irradiation. X-ray diffraction analysis indicated that the PZT films crystallized well into the perovskite phase at an
elevated temperature of 480°C by microwave irradiation. Scanning electron microscopy images showed that the
films had a granular grain structure and most of the grains were approximately 1.5 μm in size. With increasing the
elevated temperature from 480°C to 600°C by microwave irradiation, the breadth of grain boundaries of the films
became narrow and the remanent polarization of the films increased lightly. It is clear that microwave irradiation is
effective for obtaining well-crystallized PZT films with good properties at low temperatures in a short time.
LSM and annealing heat treatment on 304 stainless steel resulted in microstructures with high frequency of low ∑ CSL boundaries defined by the coincidence site lattice (CSL) model, especially, twin boundaries (∑3). The maximum frequency of the low ∑ CSL boundaries could be 88.6% under optimal processing conditions: 947°C and 28h. The high fraction of the low-∑ CSL boundaries led to a high corrosion resistance to intergranular corrosion.
Pb(Zr0.52Ti0.48)O3 thin films were prepared on Pt/Ti/SiO2/Si substrates by hybrid processing: sol-gel method and pulsed laser deposition. The temperature of postdeposition annealing in hybrid processing is 650°C, and is lower than that in the case of direct film deposition by pulsed laser deposition on a Pt/Ti/SiO2/Si substrate. The preferred orientation of the PZT films obtained by hybrid processing can be controlled using the seed layer obtained by the sol-gel process. The TEM image showed that the PZT films have a polycrystalline columnar microstructure extending throughout the thickness of the film and no shape interface was observed between the layers obtained by the sol-gel method and the pulsed laser deposition process. Electrical properties of the films were evaluated by measuring their P-E hysteresis loops and dielectric constants. The 1-μm-thick PZT films fabricated by hybrid processing consist of mainly the perovskite phase with a (111)-preferred orientation and have good ferroelectric properties. The ferroelectric parameters were remanent polarization Pr = 23.6 μC/cm2, and coercive field Ec = 54.8 kV/cm.
Pb(ZrxTi1-x)O3 (PZT) thin films were in situ-grown on Pt/Ti/SiO2/Si substrates by a hybrid process consisting of the sol-gel method and pulsed-laser deposition (PLD). The deposition temperature to obtain the perovskite phase in the hybrid process is 460°C, and is significantly lower than that in the case of direct film deposition by PLD on a Pt/Ti/SiO2/Si substrate. X-ray diffraction analysis indicated that the preferred orientation of PZT films can be controlled using the layer deposited by the sol-gel method and highly (111)- or (100)-oriented PZT films were obtained. A transmission electron microscopy (TEM) image showed that the film had a polycrystalline columnar microstructure extending through its thickness, and no sharp boundary was observed between the layers deposited by the sol-gel method and PLD. A high-resolution electron microscopy image and electron diffraction analysis revealed that the crystalline lattice of the layers deposited by the sol-gel method and PLD was continuous and there was no difference in crystalline orientation between the layers. These results indicate that the solid-phase epitaxial effect between the PZT layers deposited by the sol-gel method and PLD decreases the deposition temperature to obtain the perovskite phase during PLD, and causes the films to exhibit the same preferred orientation as that of the layer deposited by the sol-gel method. The dielectric constant and remanent polarization of the films in situ deposited at 460°C were approximately 900 and 15 μC/cm2, respectively.
Resonant-typed microscanners based on a silicon diaphragm and actuated by PZT was designed and fabricated on purpose to improve the deformed microstructure while resonating at high frequency. In order to yield large actuating force, hybrid PZT deposition process: sol-gel method and laser ablation was developed to manufacture thick PZT films with well-crystallized perovskite phase for the applications of microscanners. In our previous study, a sol-gel derived PZT was used due to the high film quality, large deposition area and easy composition control. However, to make a thick and crack-free PZT film, several times of coating and thermal treatment is not only time consumption, but increases the risk of contamination and leads the complicated problem of thermal residual stress. In this paper, the hybrid-derived PZT film with thickness of 3 μm was prepared with simplified steps and reduced processing time. Regarding to the performance of microscanners, 1D scan motion with straight patterns and scan angle of 8±1° has been demonstrated, while resonating with 7 Vp at resonance frequency (2325 Hz). The 2D scan pattern with area of (8±1°)×(5±1°) and less deformed edged was also obtained successfully due to the improvement of the silicon-based flat mirror surface.
Pb(ZrxTi1-x)O3 films were prepared by pulsed laser ablation on Pt/Ti/SiO2/Si substrates at room temperature and were crystallized by subsequent annealing. The effect of the Pb content and Zr/Ti ratio in the target on crystalline structure and electrical properites of Pb(ZrxTi1-x)O3 films was investigated. Crystalline phases and structure in the PZT films were investigated by x-ray diffration analysis (XRD). The microstructure and composition of the films were studied by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA), respectively. It was found that the adition of 20 wt% excess PbO to the PZT target is necessary to obtain a single perovskite phase. X-ray diffraction analysis results show that the film fabricated from the target with Zr/Ti ratio of 30/70 crystallizes in the tetragonal phase, while the films fabricated from the targets with Zr/Ti ratios of 70/30, 58/42, 52/48, 45/55 crystallite in the rhombohedral phase. The films derived from the target with Zr/Ti ratio of 45/55 and with 20 wt% excess PbO exhibited better electric properties. The remnant polarization and coercive field of the film were 31.28 μC/cm2 and 45.29kV/cm, while the dielectric constant and loss value measured at 1 kHz were approximately 1069 and 0.08, respectively. The results demonstrate that a few micrometers thick PZT thin films derived by laser ablation for use in micro actuators is possible.
To prepare lead zirconate titanate (Pb(ZrxTi1-x)O3): PZT) thin films at a higher deposition rate and a lower substrate temperature, the PZT films were fabricated by a hybrid process of sol-gel technique and pulsed laser ablation deposition. First, one layer of PZT (about 0.12-0.14 μm) was coated on Si/SiO2/Ti/Pt substrate by sol-gel process. Then PZT film was deposited at a rate of 0.7 μm/hr by pulsed excimer laser-ablation on the substrate with one sol-gel derived PZT seed layer. A target of Pb(Zr0.52Ti0.48)O3 with 20 wt% excess PbO was used. The substrate temperature was about 500 °C. The film fabricated by the hybrid process showed the perovskite PZT phase without pyrochlore phase. The dielectric constant measured at 1 kHz was approximately 1580. The saturation polarization, remnant polarization and coercive field of 0.8 μm thick film were about 46.6 μC/cm2, 24.5 μC/cm2 and 36.4 kV/cm, respectively. The residual stresses in the thin film stacks were measured by the changes in the radius of curvature of the wafer. A relatively lower tensile stress (approximately 33 MPa) was obtained compared to the sol-gel derived PZT film. Therefore, the PZT films with good electrical and mechanical properties can be fabricated by using the hybrid process of the sol-gel technique and laser ablation.
This paper reports the structural properties of lead zirconate titanate system formed in pulsed laser ablation deposition method. X-ray diffraction and scanning electron microscope was used for surface and the crystalline structure observation. The target material is prepared in conventional solid state reaction method using oxide powder. Formed lead zirconate titanate film has amorphous structure in as-deposited condition. Post-annealing treatment between 600 degree(s)C and 900 degree(s)C was carried out after deposition. Perovskite structure was formed on the Pt/Ti/SiO2/Si substrate after annealing treatment in all cases. The formed film has flat surface and homogeneous structure observed by scanning electron microscope.
Ferroelectric films of lead zirconate titanate (PZT) are currently attracting attention because of the large number of potential application in micro actuators, such as micro- mirror, micro-pump and multi-probe cantilever of AFM. In this study, thin films of Pb (Zr0.52Ti0.48) O3 (PZT) 1.8 to approximately 2.0 micrometer thick on a Pt/Ti/SiO2/Si substrate were prepared by excimer laser ablation and were crystallized by subsequent annealing. Crystalline phases in the PZT films were investigated by X-ray diffraction analysis (XRD). The microstructure and composition of the films were studied by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA), respectively. The effect of the Pb content of the target on electrical properties of PZT thin films was investigated. The PZT films with a well- crystallized perovskite phase were obtained by adding 20 wt % excess PbO to the target and annealing at 750 degrees Celsius for 90 min. The remanent polarization and the coercive field of this 0.8 micrometer think film were 23.6 (mu) C/cm2 and 60.0 kV/cm, while the dielectric constant and loss values measured at 1 kHz were approximately 935 and 0.04, respectively. Our results demonstrate that a few micrometers thick PZT thin films derived by laser ablation for use in micro actuators is possible.
Ferroelectric thin film is the target of the interest in micro electromechanical system, memory etc. Smart MEMS is to be developed with such smart materials thin films. In spite of the success in commercialization of FRAM application, MEMS application is still under R&D state. Despite to their promising properties, there are only few reports on the use of such layers as MEMS devices. Problems for application are mainly caused by the necessary very small dimension of such devices, in contrast to limitations and tolerances of the used micro-technologies. Although deposition of piezoelectric PZTlayer using different thin-film technologies has reached an advanced state, the layers of more than 1 micron thickness needed for MEMS applications is still difficult to deposit. To deal with these problems, the structure or the function of the devices has to be coped with such technologically caused constraints, like thickness deviation and deformation by residual stress, as well as optimization of materials processing parameters. As an application of the thin films, Piezoelectric SFM and scanning mirror device are designed and fabricated as examples of the target MEMS devices with special emphases placed on materials, processing and device structure optimization. Sol gel deposited as well as Pulsed Laser Ablation Deposited PZT layers have been developed and applied for the devices. To compensate the deformation of the devices, bimorph PZT actuator is also presented. A piezoelectric SPM is expected to provide a promising answer to High density data storage devices, as the piezoelectric layer serves as a actuator for the cantilever as well as a force sensor. This paper describes a novel probe arrays integrated with micro-heaters for the AFM thermal mechanical data storage. The probes have cantilevers 3um thick, 100-200um long, and 30-70um wide, and have micro-heater integrated on the triangle end of the cantilever. The cantilever consists of a piezoelectric layer on a silicon base for the heater actuation and force sensing. The Lead-Titanate-Zirconate (PZT) is selected as the piezoelectric material for its high piezoelectric coefficients comparing to crystal materials (for example, ZnO2). We design the heater on the triangle end of the cantilever, and shape the apex part as the narrowest to get the biggest power dissipation. The prototype of the device has been fabricated and characterized.
Micro fabrication techniques for thick structure are developed. One method is a micro fabrication method using injection molding. And another method is the coating method using hydro gel. First method is almost same technique which is named MIM or CIM. In the process, the powder is mixed with the binder and mixture is injection molded. the molded parts are extracted the binder using supercritical carbon dioxide, and sintered. Employing this process, micro pattern which has aspect ratio more than 5 can be molded by metal powder and PZT. In this method, a micro pattern made by laser ablation is used as a die. As compared with other micro fabrication techniques, this method can utilize the molding die repeatedly. Consequently, the producing cost of micro parts can be decreased by this method on actual production process. Second method is a technique which uses the PVA hydrogel. The powder is mixed with water which contains the PVA from 3 to 15 percent. The mixed compound is sandwiched with PE films.It is froze and a gel sheet which has thickness from 40 to 100 micrometers is obtained. Using the sheet, the ceramic and metal are coated on the Silicon wafer, and thick structure is fabricated.
Crack-free ferroelectric thin films of lead zirconate titanate with thickness of 3 micrometers for microactuators were fabricated using Sol-Gel spin-coating onto Pt/Ti/SiO2/Si substrates. The precursor solution was prepared from lead acetate, zirconium-n-propoxide and titanium tetraisopropoxide. 2-propanol was used as the solvent. The crystalline phase as well as preferred orientation in the PZT films were investigated using x-ray diffraction analysis. The microstructure and composition of the films were studied by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy, respectively. The well-crystallized perovskite phase and the preferred orientations in the direction of the (100) plane were obtained using the heat treatment for dry at 120 degrees C, for pyrolysis at 300 degrees C and for crystallization at 600 degrees C. The prepared films showed nanometer grains with smooth and uniform surface. The dielectric constants and loss values of these films measured at 1 kHz were approximately 1250 and 0.04, respectively, while the remnant polarization and the coercive field were 45.5 (mu) C/cm2 and 58.5 kV/cm. Our results suggest that fabrication of good structural quality PZT films of a few micrometers thick for use in micro actuators is possible.
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