0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMNT) thin films were prepared on (111)Pt/Ti/SiO2/Si substrate by a modified sol-gel process with Nb2O5 as the niobium source. XRD analysis shows that PMNT thin films with pure perovskite were obtained by spin-coating and annealing at 700°C for 20 minutes. The remanent polarization and coercive field of the PMNT thin films are about 7.69μC/cm2 and 80.75kV/cm, respectively. The dielectric and C-V curve of PMNT thin films are also investigated. The dielectric constant ( εr ) reaches 935 and the dissipation factor (tanδ)is about 0.04 at 1kHz.
Two types of readout integrated circuit named SFD and CTIA are proposed to match the PVDF pyroelectric IR detector.
By employing macro model and analyzing the parameters of detector, the best matching conditions including the input
reference noise, input impedance, input capacitance, and working point are investigated in details. Based on the property
of the AC output for PVDF detector, we propose a novel readout method, with which the ratio of signal to noise can be
greatly improved. Furthermore, the linearity and sensitivity for both circuits are discussed by the means of Spectre tools.
(Ba,Sr)TiO3 (BST) thin films were deposited on the conducting perovskite LaNiO3 electrode by radio-frequency (rf)
magnetron sputtering technique. To investigate the crystalline of BST films, the substrate temperatures (Td) in the range
of 100°C-700°C were applied. The transition from amorphous phase to polycrystalline phase for the films occurred at
low growth temperature 300°C. When the growth temperature approached 500°C, highly (h00)-oriented films were
obtained. The relative dielectric constant (εr) increased rapidly with enhancing growth temperature because of improved
crystallinity, and showed slowly increase above 500°C. In addition, the capacitance-voltage characteristics were studied
with various growth temperatures. The tunability increased largely with good crystallinity. This can be attributed to
increased dielectric constants.
Using Landau-Devonshire(LD)-type phenomenological model, we investigate the phase diagrams and in-plane
anisotropic misfit strains of single-domain single-crystal (110) Ba0.6Sr0.4TiO3 film epitaxially deposited on (001)
NdGaO3 substrate. Investigation indicates that film thickness plays a crucial role on formation of in-plane anisotropic
misfit strains and stable phases. As is consistent with results of experiment that anisotropic strains have greatly changes
with increase of film thickness. The anisotropic strains induce tetragonal phases which only contain in-plane spontaneous
polarization component. These phases do not exist in BST films of the same composition under isotropic strains.
Moreover, calculation manifests that anisotropic in-plane misfit strains are almost completely relaxed when film
thickness is larger than 600nm, which has been reported in experiment.
SrTiO3 (STO) thin films were grown on Si(100) substrates by RF magnetron sputtering. The substrate temperature was
found to be a crucial parameter to obtain the highly (h00) oriented growth. At the substrate temperature of 700 °C, STO
thin films with the (h00)-orientation parameter (αh00) of more than 93% were realized. Using vitreous silica as the
substrate, the optical properties of STO thin film prepared at 700 °C were investigated by transmittance measurements.
The fitting method was used to calculate the refractive index and the film thickness from the transparent region of the
transmittance spectra. The dispersion of the refractive index was studied by considering a single electronic oscillator
model. According to Tauc's law, the band gap of the film was found to be about 3.62 eV.
The BaTiO3 and Mn:BaTiO3 thin films were fabricated on fused quartz and Si(111) substrates by a sol-gel method. The crystal structures of the samples were characterized by x-ray diffraction. It is shown that the samples are both polycrystalline thin films and possess cubic structure. The Mn-doping has no obvious effect on the crystal structure. The optical properties of the thin films were studied by transmitted spectrum technique or by spectroscopic ellipsometry depending on the substrate used. The transmitted spectrum shows that the absorption edge of the Mn-doping films has red shift compared with the undoping films. The energy gaps calculated from the transmitted spectrum are 3.68 and 3.39eV for undoping and Mn-doping samples, respectively. The results of spectroscopic ellipsometry shows that the refractive index of the Mn:BaTiO3 thin film is bigger than that of the BaTiO3 thin film. Which the change of energy gap and refractive index caused by Mn-doping can be explained by the Sellmeier Oscillator model.
92%Pb(Mg1/3Nb2/3)O3-8%PbTiO3 (PMNT) thin films on Pt/TiO2/SiO2/Si substrates with and without a LaNiO3 (LNO) buffered layer have been prepared using a sol-gel method. Structures and electrical properties of these two films have been investigated and compared. Highly (111)-oriented PMNT thin films with some amounts of pyrochlore phase are obtained on bare Pt electrodes. On the contrary, (100)-oriented PMNT thin films with pure perovskite phase are formed on Pt electrodes with a LNO buffered layer. Electrical properties of the PMNT thin films are highly improved by using the buffered layer LNO. It is found that the remanent polarization (Pr) and the dielectric constant for the PMNT film with a LNO buffered layer are larger than that for the film without a LNO buffered layer.
Highly (100)-oriented LaNiO3-δ (LNO) thin film were grown on n-type Si(100) at substrate temperature 200°C with 40% oxygen partial pressure. The as-deposited LNO films are metallic and have a resistivity of ~9×10-4 mΩcm at room temperature (RT) and can be used as the bottom electrode for the fabrication of integrated ferroelectric capacitors on Si. A post-annealing process can decrease the RT resistivity to ~3×10-4 Ωcm at 700°C and yield crack at 800°C.
Electrically conductive LaNiO3-δthin film with perovskite-type structure were deposited on Si(100)/n substrates by rf magnetron sputtering at substrate temperature 200°C , 300°C, 450°C, 600°C with a series of 0%, 20%, 40%, 60% oxygen partial pressure respectively. The La2NiO4 and NiO peak of XRD are not observed. The RT resistivity of LNO films decreases with the decreasing substrate temperature at a fixed oxygen partial pressure and with increasing oxygen partial pressure at a fixed substrate temperature.
The structure and ferroelectric properties of Bi3.25 La 0.75Ti3O12 (BLT) and Bi3.25 Nd0.75Ti3O12 (BNT) thin films deposited on (111)Pt/Ti/SiO2/Si substrates using a metalorganic decomposition (MOD) method were investigated. Both the films were polycrystalline structure with the single bismuth-layered phase. The BNT film showed the (117) random orientation, while the BLT film displayed (00l)-preferential orientation. The BNT film showed a larger remnant polarization (~13.8μC/cm2) than the BLT film (~3.5μC/cm2), while both films displayed almost the same value of coercive field. The BNT film had the larger dielectric constant and a litter larger dissipation factor than the BLT film. The superior ferroelectricity of the BNT film was mainly attributed to its (117) random orientation. Furthermore, the BNT film displayed good fatigue endurance up to 109 switching cycles, indicating it was a useful candidate for integrated device applications.
2 mol% Lanthanum doped lead zirconate titanate Pb(Zr0.4Ti 0.6)O3 ferroelectric thin film were successfully deposited by a modified sol-gel method on(111) Pt/Ti/SiO2/Si(100) substrate, the effect of heat-treatment on the properties of microstructure and ferroelectric was investigated. It is shown that deposited on (111)Pt lead to (111) preferred orientation. The PLZT thin film annealing at 700°C show good ferroelctric properties with a large remnant polarization of 40μ C/cm2, a spontaneous polarization of 75.7μ C/cm2, and a coercive field of 112kV/cm under an electric field of 650kV/cm. The dielectric constant increased with annealing temperature.
The temperature dependence of pyroelectric coefficient in LB films of hemicyanine dyes with different thickness has been investigated. It was found that, in the range from 20 to 45°C, the pyroelectric coefficient was not almost changed for the film thickness less than 32 monolayers. However, the one was enhanced obviously with temperature increasing for the film thickness larger than 32 monolayers. The facts indicated that there is a critical thickness in the ferroelectric LB multilayer films. For the LB films of 20 and 30 monolayers, we can observe two peaks in the temperature dependence of pyroelectric coefficient (at 9 and/or 12°C) under heating and/or cooling processes. But, the heat-hysteresis was not found in 40 monolayers LB films. It is indicated that there are the heat-hysteresis and further confirmed the existence of phase transition in the LB films in the neighborhood of 10°C. It may be demonstrated primarily that the type of phase transition is the surface first-order ferroelectric-paraelectric phase transition by the pyroelectric coefficient measurement.
Distributed parameter model is used for computation of the performances of single pixel of PZT ferroelectric thin film infrared uncooled focal plane array (IR-UFPA) with two kinds of thermal isolation structures. The detector performances are found to be related closely to the thermal isolation structure. The preferred thickness of pyroelectric thin film is in the region of 0.3 - 2 micrometers for pixel dimensions 50 X 50 and 100 X 100 micrometers 2. And the preamplifier current noise is the dominant noise when it more than 10-16 A(DOT)Hz-1/2 in PZT-UFPA device.
LaNiO3 (LNO) thin films on Pt/Ti/SiO2/Si substrates were prepared by a simple chemical solution technique using lanthanum nitrate and nickel acetate as the start materials. A subsequent Pb(Zr0.50Ti0.50)O3 thin film annealed at 550 degree(s)C on the LNO-coated Pt/Ti/SiO2/Si substrate was prepared with a modified sol-gel process. The techniques of x-ray diffraction and scanning electron microscopy were used to characterize the structure of the films. All the electrical measurements were carried out in a Pt-ferroelectric-LNO/Pt configuration. Pt was sputter deposited into the sample using a mask and the bottom electrode (LNO/Pt) was etched to be exposed by ion etching technique. The resistivity of the LNO film and the ferroelectric and fatigue properties of the Pt/PZT/LNO/Pt/Ti/SiO2/Si capacitor were measured by the four-point probe method and RT66A system, respectively. The LNO film shows good metallic property, which is comparable with the LNO films derived from physical techniques. It is found that the PZT thin film annealed at 550 degree(s)C is pure perovskite phase with highly (001) orientation, even though the LNO layer is randomly oriented polycrystalline. The ferroelectric capacitor derived from these films displayed a good P-E hysteresis loop at an electric field of 200 kV/cm with Pr and Ec of 16.6 (mu) C/cm2 and 46 kV/cm. The PZT thin film capacitor does not show obvious drop in polarization up to 109 switching cycles.
Highly (100)-oriented lead zirconate titanate Pb(Zr0.52Ti0.48)O3 thin films with and without a PbO- coated layer were prepared on LaNiO3 (LNO)-coated silicon substrates by a simple sol-gel process. X-ray diffraction and atomic force microscope were applied to study the microstructure of the films. The ferroelectric and fatigue properties were measured by a RT66A system. An infrared spectroscopic ellipsometer was used to determine the thickness of the thin films. The leakage current density (J-t) was carried out with a Keithley 617 programmable electrometer. All measurements were conducted on a Pt-PZT- LNO capacitor structure. It was observed that the PbO-coated layer has no effect on the texture of the PZT thin films while it leads to a great improvement in the surface morphology. The results indicated that samples with a PbO- coated layer show higher remnant polarization and lower coercive field (18.6 (mu) C/cm2 and 58.5 kV/cm) than that of samples without PbO-coated layer. After 108 switching cycles, the net-switched polarization for the film with a PbO-coated layer does not show any drop.
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