Ferroelectric PZT Thin Films Research Articles

Photoinduced modification of optical properties of ferroelectric PZT thin films

This study investigates ultrafast photoinduced changes in optical properties of ferroelectrics (PZT) on femtosecond to nanosecond timescales, using broadband transient reflectivity studies. Surprisingly, spectral features were observed below the bandgap, which could not be attributed to ground state bleaching, excited state absorption, and/or stimulated emission. A model based on probe energy independent changes in refractive index and extinction coefficient showed good agreement with experimental results. Three relaxation processes were phenomenologically considered for the temporal evolution. Laser-induced heating was ruled out as the cause of short timescale behavior and photorefractive effect was suggested as a potential mechanism for changes in the optical properties.Graphical abstract

Preventing Color Fading in Artist’s Oil Paintings Based on Nano-PZT Ferroelectric Thin Film

Due to the excellent electrical properties, stable temperature characteristics, and abundant material systems of ferroelectric thin film materials, in recent years, ferroelectric devices based on silicon technology have been used in microelectronic mechanical systems, new energy photovoltaics, especially nonvolatile memory and other fields. During the preservation of the artist’s oil painting works, the temperature change will directly cause the physical effects of thermal expansion and contraction of the oil painting and the chemical reaction speed of the material in nature. Therefore, it is of great significance to introduce the technology of nano-PZT ferroelectric thin film into oil paintings to prevent fading. This article aims to study the research on preventing fading of the artist’s oil paintings based on nano-PZT ferroelectric thin films and analyze the characteristics of ferroelectric materials, the application of ferroelectric films, the preparation methods of ferroelectric films, and the basis of the main environmental factors that affect the fading of oil paintings. In the above, we studied the fading process of different concentrations of oil paints under simulated sunlight aging and the effect of different concentrations and thicknesses of PZT ferroelectric thin films coated with nano-TiO2 coatings on the color stability of oil paints. The experimental results show that after five times of simulated solar aging for the four concentrations, the total color difference △E: 0.05% group is the largest, 0.4% group is the smallest, the higher the oil paint concentration, the smaller the color difference, the better the color stability, and the antisimulation of sunlight fading.

Research on photosensitive gate ferroelectric integrated GaN HEMT photodetector

In this paper, we take advantage of the high sensitivity of two-dimensional electron gas concentration in the heterojunction channel of a GaN high electron mobility transistor (HEMT) to device surface states and gate voltages. By integrating a HEMT with ferroelectric materials with photovoltaic effects, a photo-sensitive gate HEMT photodetector based on ferroelectric integration is obtained. By exploring the ferroelectric and composite film sputtering growth epitaxial atmosphere, a high-performance PZT/ZnO composite ferroelectric film grown in an oxygen-containing atmosphere is obtained. Comparing the PZT and LiNbO3 (LN) ferroelectric thin films prepared with or without the buffer layer, the following conclusions are obtained. The quantum efficiency of the PZT/ZnO film increases by 240% and 596% at the peak of 300–400 nm, reaching 14.55%; the residual polarization of the PZT film obtained in an oxygen-containing atmosphere reaches 52.31 μC/cm2; the PZT/ZnO composite film has better fatigue characteristics. The GaN HEMT detector prepared by using magnetron sputtered PZT/ZnO as the sensing gate under the oxygen atmosphere has a photocurrent increment of 11.51 mA under ultraviolet light and a responsivity of 111A/W at 365 nm. At the same time, the device has τr = 0.12 s and τf = 8.3 s transient response. The research in this paper shows that a new structure photodetector based on a GaN HEMT has excellent ultraviolet light response, which provides a new research direction for the light detection mechanism.

Sem Image Based on Denoising Algorithm Shows the Effect of PTO Seed Layer on the Crystallization Temperature and Electrical Properties of PZT Ferroelectric Thin Films

Sem Image Based on Denoising Algorithm Shows the Effect of PTO Seed Layer on the Crystallization Temperature and Electrical Properties of PZT Ferroelectric Thin Films

Effect of substrates on optical properties of ferroelectric PZT (52/48) thin films

The last few years have seen an upsurge in attention towards the investigation and application aspect of the electro-optic properties of ferroelectric materials. The current work reports the effect of substrates on the optical characteristics of the lead zirconate titanate (PZT) thin films fabricated via the novel sol–gel route. The PZT thin films were deposited on to three different substrates i.e. corning glass, ITO glass, and Quartz by spin-coating technique. The thin film samples were tested for their structural and optical properties via XRD, Raman, and UV–Vis spectroscopy. The XRD patterns revealed formation of perovskite crystal structure when the samples were calcined at 650 °C for 2 h. The optical energy band gap values for the thin film samples varied with the substrates and were reported to be 3.55 eV for corning glass, 3.59 eV for ITO glass and 3.79 eV for Quartz.

Ferroelectric PZT thin films for photovoltaic application

The ferroelectric photovoltaic response characteristics of Lead Zirconate Titanate (PZT) thin film in metal-ferroelectric-metal (MFM) configuration is studied under 33 mode upon exposure to UV radiations. PZT thin films of 180 nm are prepared on inter-digital electrodes patterned silicon substrate (with silicon dioxide as insulating layer) using chemical solution deposition (CSD) technique followed by rapid thermal annealing. PZT thin films are found to be in single phase and possess high electrical polarization (50μC/cm2). Significant increase in photocurrent and large value of open circuit voltage (1.0 V) is observed for the prepared ferroelectric photovoltaic film under UV illumination.

Time dependence of different contributions for the photovoltaic effect in ferroelectric PZT thin films with asymmetric electrodes

In this work the photovoltaic response of ferroelectric Pb(Zr0.20Ti0.80)O3 (PZT) thin films, with asymmetric Metal/Ferroelectric/Metal structure (Au/PZT/ITO), was investigated and its effect correlated to the ferroelectric and interface properties. We found two effects governing the photovoltaic response in these thin films, a depolarization electric-field (Edep), dependent on the direction and magnitude of the polarization, and an internal built-in electric field (Ebi) which could be generated by the different electrodes and processing conditions. The time dependence of the photocurrent showed a strong reduction of the photocurrent after poling, probably related to a reaccommodation of charges and back-switching of the polarization, due to the rearrangement of the domain structure in the material.

A comparative study on macroscopic and nanoscale polarization mapping on large area PLD grown PZT thin films

By optimizing laser raster scanning conditions and controlling PbO evaporation, we have grown high quality large area PbZr.52Ti.48O3 (PZT) thin films using custom-built off-axis pulsed laser deposition (PLD) technique. The realization of high quality PZT thin films over a large area with uniform polarization is a challenging task due to the formation of non-ferroelectric or pyrochlore like PbTi3O7 phases at the processing temperature (>600°C). Our results show the polycrystalline nature of the sample with a uniform chemical surface composition. The macroscopic level of polarization mapping shows excellent saturated P-E loops with a narrow variation (6%) of the remnant polarization (2Pr) across the large area thin films. A comparative study of macroscopic and nanoscale level of mapping of polarization switching are performed, to demonstrate the existence of stoichiometry ferroelectric PZT thin films over a large area. The achievement of high quality large area PZT thin films with uniform polarization might be used for under-water SONAR devices and in power harvesting.

Using Ferroelectric Thin Film as the Dielectric for Electrowetting-on-Dielectric

In this paper, the dielectric and electrowetting properties of Pb (Zr0.4Ti0.6)O3 (PZT) ferroelectric thin film are studied as the dielectric layer in electrowetting-on-dielectric (EWOD) device. The PZT thin film is formed by spin-coating, pyrolysis and annealing. The characterization results show that PZT thin film can serve as the dielectric of EWOD with a high dielectric constant and a great electrowetting performance when used in silicon oil bath environment. To test the electrowetting effect, a EWOD device with 200nm thick PZT ferroelectric thin film dielectric layer is fabricated. The variation of contact angle between droplet and device surface achieved with DC voltage, AC voltage and AC frequency change of electrowetting on PZT are fully experimented. The EWOD device with PZT dielectric layer can manipulate water droplet at low driving voltages. This study shows the potential of using ferroelectric ceramic material as the dielectric layer in high-performance EWOD devices.

Dielectric Breakdown and Failure of Ferroelectric Films as the Dielectric for Electrowetting Systems

In this paper, we study the electrical properties and breakdown phenomena of PZT ferroelectric thin film in electrowetting systems. The experimental results indicate that irreversible charge trapping occurred with repeated voltage actuation, resulting in contact angle relaxation and reduction of the ferroelectric film breakdown strength. The breakdown voltage depends on DC voltage polarity, and this polarity dependence was found to be related to the thickness of the ferroelectric layer. When AC voltage was applied, the breakdown voltage increased directly with voltage frequency. These phenomena are interpreted in terms of electrochemical reactions at the liquid/solid interface, an empirical model was used to estimate the amount of trapped charge in the ferroelectric film.

Positive/negative electrocaloric effect induced by defect dipoles in PZT ferroelectric bilayer thin films

Double hysteresis loops induced by defect dipoles are obtained in PbZr0.52Ti0.48O3/PbZr0.8Ti0.2O3 ferroelectric bilayer thin films prepared by a sol–gel method.

Influence of oxygen partial pressure on the properties of PZT thin film deposited by RF magnetron sputtering

In magnetron sputtering systems, lead-zirconium-titanium oxide (PbZr1−xTixO3 or PZT) thin films were prepared in a mixture atmosphere of Ar and O2 with various oxygen partial pressures (0, 0.5, 1, 1.5 and 2% oxygen). About 600 nm PZT ferroelectric thin films were deposited on substrates, and then annealed at 600°C for 35 s. The structural, electrical and ferroelectric properties of PZT films were studied. As the oxygen partial pressure increased, the remanent polarisation rose first and went down later, and the leakage current density decreased first and then increased. At the oxygen partial pressure of 0.5%, we obtained the largest remanent polarisation and the minimum leakage current density. The XRD diffraction spectrum of all films displayed predominant (111) preferred orientation, and there was a weak XRD diffraction peak of pyrochlore phase in the PZT films deposited in pure Ar.

1550 nm modulating retroreflector based on coated nanoparticles for free-space optical communication.

Nowadays, there is a renaissance in the field of space exploration. Current and future missions depend on astronauts and a swarm of robots for reconnaissance. In order to reduce the power consumption, weight, and size of the robots, an asymmetric communication system may be used. This is achieved by installing modulating retroreflectors (MRRs) on one side of the link and an interrogating laser on the other side. In this paper, we theoretically study an innovative device that can serve as an MRR in the infrared range of the spectrum. The device is based on a ferroelectric PZT thin film containing TiO2 coated Ag nanoparticles, which exhibit strong plasmonic resonance in the infrared range. After intensive analyses, which included calculations and simulations, we were able to design the device to operate at the 1550 nm wavelength. This is of great importance since the design of devices operating at 1550 nm as this wavelength is a mature technology widely used in free-space optics. Hence, this MRR can serve in asymmetric communication links relying on 1550 nm transmissions, which are also eye-safe. To the best of our knowledge, this is the first time coated metal nanoparticles have been proposed to modulate light in the infrared region. The performance of this device is unique, reaching a 17.5 dB modulation contrast with only a ±2 V operating voltage. This modulator may also be used for terrestrial communication such as fiber optics and optical interconnects in future data centers.

The conductivity mechanism and an improved C−V model of ferroelectric PZT thin film

A dense, homogeneous and crack-free ferroelectric PZT thin film with 〈100〉-preferred orientation was produced using the sol-gel method. The volume fraction α(100) of 〈100〉-oriented grains in the PZT film was calculated [α(100) ≈ 80%] from XRD of the PZT thin film and powder. The PZT thin film exhibits an open polarization vs. electric field loop and a low leakage current density from 10−8 A/cm2 to 10−7 A/cm2. The electrical conduction data were fit to a Schottky-emission model with deep traps from 100 kV/cm to 250 kV/cm. A modified capacitance model was introduced that adds electrical domain capacitance based on a metal-ferroelectric-metal (MFM) system with Schottky contacts. The model reproduces the observed non-linear capacitance vs. voltage behavior of the film.

Modeling ferroelectric permittivity dependence on electric field and estimation of the intrinsic and extrinsic contributions

The nonlinear dependence of the dielectric permittivity on electric field ε(E) is modeled by the relationship ε(E) = ε00 + 1/(α + β Eeff2), where Eeff = E + κ P(E). Using an appropriate mathematical representation of the polarization loop P(E), it is possible to describe correctly the hysteretic behavior of the curve ε(E). This model allows the separation of the intrinsic and extrinsic contributions to the dielectric response from the experimental measurement of ε(E). The model is validated for PZT and PLZT ferroelectric thin films. It is shown that the polarization hysteresis loop can be reconstructed from the curve ε(E), which can be very useful for separating polarization current from leakage current in ferroelectric samples.

Ferroelectric thin film fabrication by direct UV-lithography

Due to their use in the fields of sensors, energy harvesting, capacitors and FeRAMs the fabrication of microstructured ferroelectric thin films is an important research field. Therefore a modified sol---gel process chain has been developed to produce fine patterned ferroelectric PZT (PbZr0.52Ti0.48O3) thin films by direct UV-lithography. A sol based on methacrylic acid was developed to provide a photosensitive metal organic PZT precursor. The sol was used to obtain photosensitive xerogel films by spin-coating, which were patterned using conventional UV-photolithography equipment. After development the patterned xerogel films were pyrolized and crystallized in air via rapid thermal annealing in order to obtain crystalline PZT thin films. The patterned PZT films were investigated by XRD technique and SEM-micrographs. Finely patterned, crack free, crystalline PZT thin films were obtained.

Low-temperature preparation and characterization of the PZT ferroelectric thin films sputtered on FTO glass substrate

Abstract Pb(Zr 0.52 Ti 0.48 )O 3 ferroelectric thin films were in situ deposited on FTO glass substrate by RF magnetron sputtering process at low substrate temperature of 260 °C, through optimizing the process parameters of sputtering power, sputtering gas pressure, and substrate temperature. Ferroelectric properties, surface morphology, and optical transmittance of PZT thin films are investigated by standardized ferroelectric test system, atomic force microscope, and UV–Vis spectrometer, respectively. The results show that the sample deposited at 260 °C exhibits ferroelectric properties with P r and P s of 3.86 μm/cm 2 and 8.85 μm/cm 2 , respectively. The arithmetic average roughness PZT thin film is 95.9 nm. Interestingly, the mean transmittance of the sample is above 80% in the visible light range.

EXAFS study of PZT ferroelectric thin films of different crystallinities

Lead zirconate titanate (PbZrxTi1-xO3, PZT) thin films were deposited on Pt/TiOx/SiO2/Si substrate by RF-magnetron sputtering with a Pb1.2Zr0.3Ti0.7O3 target at room temperature. The Zr K-edge of PZT thin films of different crystallinities were studied by extended x-ray absorption fine structure (EXAFS) spectrum. Scans were made in fluorescence mode to monitor the structural differences between the amorphous thin films and the crystalline thin films. It was found that the local structure of the amorphous thin films was quite different from that of the crystalline thin films from the analyses of the EXAFS spectra. In the amorphous PZT thin films only one oxygen coordination shell can be found. By contrast, in the crystalline PZT thin films, the EXAFS spectrum was fitted with three shells and Zr-Pb bond was found. The oxygen coordination numbers of the amorphous and crystalline PZT thin films were same. The Zr-O bond distance of the amorphous samples were bigger than the crystalline samples. Thus, the influences of the phase transformation on the ferroelectric properties of PZT thin films were interpreted from the angle of the local chemical structures.

Synthesis and Characterization of PZT Thin Films Embedded with WO3 Nanoparticles by a Hybrid Chemical Solution Route

PZT thin films embedded with WO3 nanoparticles were prepared by a hybrid chemical solution process. WO3 at 0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1 wt% nanopowders were suspended in an organometallic precursor solution of PZT, and then coated on platinized silicon substrate using spin-coating technique. The increase of WO3 resulted in a reduction of densification of the films. However, at 1 wt% WO3 concentration, the reaction between PZT and WO3 occurred during heat-treatment process at 600°C and seemed to improve the film's density. The WO3 nanoparticles were also found to affect both dielectric and ferroelectric properties of PZT films. Moreover, the addition of WO3 nanoparticles was found to improve a fatigue phenomenon in ferroelectric PZT thin films.

Preparation of PZT Ferroelectric Thin Films by Sol-Gel Process

Sol-gel method is used for the formation of Pb(Zr0.63Ti0.37)O3(PZT) thin films. The initial films were formed with spin coating sol solution on silicon wafer and drying coated wet sol film at 300°C for 5min. This process was repeated for 1-4 times to obtain 4 initial films with different thicknesses. 4 initial films were annealed at 500°C for 2h to obtain PZT ceramics films. The morphologies of the surface and cross-section of PZT films were observed with a scanning electronic microscope (SEM). The phase structures of PZT films were analyzed using an X-ray diffraction meter (XRD). Experimental results show that PZT film prepared by coating wet sol on silicon once can be high smooth and compact film.