Photovoltaic (Pb,La)(Zr,Ti)O3 (PLZT) films in a layered structure of different crystallographic orientations are
fabricated by an optimized metalorganic deposition (MOD) method. Such films of (001) orientation exhibit a
photovoltaic electrical power of approximately 20 times higher than that of random films. The anisotropic optical
properties of the oriented films, including dark conductivity, photoconductivity and photovoltaic tensor surfaces, are
obtained quantitatively. These results show that the photovoltaic output current and power of the oriented films are
highly improved to be equal to those of semiconductors and suitable for application in the optical sensor of micro-electro-mechanical systems (MEMS).
We proposed one novel MEMS-based thermometer with low power-consumption for animal/human health-monitoring
network application. The novel MEMS-based thermometer was consisted of triple-beam bimorph arrays so that it could
work in a continuous temperature range. Neither continuous electric supply nor A/D converter interface is required by
the novel thermometer owing to the well-known deflection of bimaterials cantilever upon temperature changes. The
triple-beam structure also facilitated the novel thermometer with excellent fabrication feasibility by conventional
microfabrication technology. The parameters of the triple-beam bimorph arrays were determined by finite element
analysis with ANSYS program. Low stress Au and Mo metal films were used as top and bottom layer, respectively.
The deflection of the triple-beam bimorphs were measured on a home-made heating stage by a confocal scanning laser
microscopy. The novel bimorphs had temperature responses similar to traditional single-beam bimorphs. Initial bend of
the prepared triple-beam bimorphs were dominantly determined by their side beams. The sensitivity of the novel
thermometer was as high as 0.1°C. Experimental results showed that the novel thermometer is attractive for network
sensing applications where the power capacity is limited.
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.
Photovoltaic (Pb,La)(Zr,Ti)O3 (PLZT) films in a layered structure of different crystallographic orientations are fabricated by an optimized metalorganic deposition (MOD) method. Such films of (001) orientation exhibit a photovoltaic electrical power of approximately 20 times higher than that of random films. The anisotropic optical properties of the oriented films, including dark conductivity, photoconductivity and photovoltaic tensor surfaces, are obtained quantitatively. These results show that the photovoltaic output current and power of the oriented films are highly improved to be equal to those of semiconductors and suitable for application in the optical sensor of micro-electro-mechanical systems (MEMS).
The present study reports the sol-gel deposition of PZT thick films on Pt/Ti/SOI substrate and its application to the micro cantilevers and 2D micro optical scanning mirrors. Crack-free PZT thick films (2.7 µm) have fabricated on Pt/Ti/SOI substrate. Thin SiO2 layer on the top of the SOI substrate was found to play important role as a burrier layer to avoid breaking the Pt/Ti bottom electrode layer. The micro cantilevers and 2D micro scanning mirrors fabricated by MEMS technologies are flat suggesting the advantage of using SOI substrate instead of Si substrate. The deflection of the tip of the 800 µm-long x 250 µm-width micro cantilever was measured to be 5.9 µm at 5 V. The absolute value of the transverse piezoelectric constant |d31| of the PZT thick film calculated from the deflection is as high as 84 pC/N. The scan angle of the cantilever via resonant actuation at 2387 Hz is as high as 40 degree with only 6 V (peak-to-peak). The response time of micro cantilevers were measured to be within 0.3-1 ms. These data indicate the potential application of the present 2D micro scanning mirrors to wavelength division multiplexing (WDM) systems driven at several voltage.
This paper reports on the formation of a new layered film structure and the highly improved photovoltaic output of the lead lanthanum zirconate titanate (PLZT) employed. PLZT film was deposited onto a Pt/Ti/SiO2/Si substrate and sandwiched vertically between electrodes. The new structure design is described using a top transparent indium tin oxide (ITO) electrode. Inspection by X-ray diffraction revealed that the PLZT film had a perovskite structure. The PLZT film structure exhibited V and μA output. This means that the photovoltaic current of the PLZT film per unit width was more than 102 times larger than that of bulk PLZT, while the photovoltaic voltage per unit thickness in the layered film structure was almost the same as that in bulk ceramics. These differences are due to the characteristics of the film structure and configuration of the electrode. In addition to the photovoltaic output the PLZT film also has the advantage of its easily controllable parameters: film thickness, illuminated area and illumination intensity. A simple model is used for the phenomenological explanation of the improved photovoltaic effect of the PLZT film.
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.
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.
Although piezoelectric thin films are of great interest for actuator application in MEMS, deposition of PZT films with thicknesses between 5 and 100 micrometers has been hardly possible. It is therefore the goal of this paper, to investigate the properties of PZT-films of this thickness deposited by the recently introduced Jet-Printing System, especially concerning an application in micro actuator devices. First, PZT layers of thicknesses between 5 and 80 micrometers have been Jet-Printed on different substrates to investigate the compatibility of the deposition method with standard materials used for MEMS. The relative dielectric constant of the layers could be determined between 20 and 550, depending on annealing and deposition conditions. Following, on thin beam-shaped steel substrates PZT layers of 10 to 40 micrometers thickness were deposited. SInce the samples showed deformation caused by technology-introduced stress, the stress value is calculated by means of FEM calculation, and methods for avoiding and compensation of the deformation are introduced. Using the beam-shaped samples, for the first time the piezoelectric constant of the Jet-Printed PZT-layer was calculated to 20...30 10-12 C/N from laser measurements of static and quasi-static beam deflection, and therefore piezoelectric actuation capability could be proofed directly.
To close the technological thickness gap between vary thin PZT-layer deposition and bulk PZT, a new technology called Jet Printing has been introduced recently, which can be used to deposit layers between 5 and 100 micrometers thickness. This technology is used for the first time to fabricate bimorph actuator elements suitable for actuation purposes in MEMS. At first, 10 to 40 micrometers thin PZT layers are deposited on beam shaped structures made of 30 micrometers thick steel. This basic actuator beams were stimulated by an AC voltage, and the reflected laser beam showed reasonable dynamic deflection angels of about 5 degrees maximum. Secondly, deposition on anisotropically etched silicon membranes with varying thickness from 25 to 125 micrometers was carried out. It appeared, that at a membrane thickness lower than 50 micrometers technologically effects can break the membrane. However, for membranes thicker than that, direct deposition after anisotropic etching could be applied successfully, and dynamic deflection of this membranes could be proofed by laser interferometric measurement. Finally, a small structure capable of diverting a laser beam and carrying out 2D scanning was designed and fabricated from 30 micrometers thick steel using laser ablation. The scanner is actuated by four actuator beams, on which 30 micrometers thick PZT has been Jet Printed as the actuating material. The electrodes on the beams can be stimulated separately, and therefore control the scanning direction. Experiments showed the capability of the structure to be actuated, and deflection angels up to 5 degrees could be measured.
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