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1.
Potts-Ising model for simulation of polarization switching in polycrystalline ferroelectrics 下载免费PDF全文
This paper proposes a scheme based on the Potts and Ising models for
simulating polarization switching of polycrystalline ferroelectrics
using the Monte Carlo method. The polycrystalline texture with
different average grain size is produced from the Potts model. Then
Ising model is implemented in the polycrystalline texture to produce
the domain pattern and hysteresis loop. The domain patterns and
hysteresis loops have been obtained for polycrystalline texture with
different average grain size. From the results of domain pattern
evolution process under an applied electric field using this scheme,
an extended domain, which covers more than one grain with
polarization aligned roughly in the same direction, has been
observed during the polarization reversal. This scheme can well
reproduce the basic properties of polycrystalline ferroelectrics and
is a valuable tool for exploring the physical properties of
polycrystalline ferroelectrics. 相似文献
2.
Ferroelectric Properties of Polycrystalline Ceramics with Dipolar Defect Simulated from the Potts--Ising Model 下载免费PDF全文
Physical properties of polycrystailine ferroelectrics including the contributions of the fixed dipolar defects and the average grain size in the Potts-Ising model are simulated by using the Monte Carlo method. Domain pattern, hysteresis loop and switching current of the polarization reversal process are obtained. Two processes are considered in our simulation. In the first one, the grain texture of ferroelectric ceramics are produced from the Ports model, and then the Ising model is implemented in the obtained polycrystailine texture to produce the domain pattern, hysteresis loop and switching current. It is concluded that the defect has the ability to decrease the remnant polarization P~ as well as the coercive field E~. The back switching is obviously observed after the electric field is off, and it shows some variation after introducing the fixed dipolar defect. Meanwhile, the spike of the switching current is found to lower with the increasing defect concentration and the decreasing average grain size. 相似文献
3.
Artificial Modulation of Ferroelectric Thin Films into Antiferroelectric through H+ Implantation for High-Density Charge Storage 下载免费PDF全文
Hydrogen ions are implanted into Pb(Zro.3Tio.7)03 1014 ions/cm^2. Pseudo-antiferroelectric behaviour in thin films at the energy of 40keV with a flux of 5 x the implanted thin films is observed, as confirmed by the measurements of polarization versus electric hysteresis loops and capacitance versus voltage curves. X-ray diffrac- tion patterns show the film structures before and after H+ implantation both to be perovskite of a tetragonal symmetry. These findings indicate that hydrogen ions exist as stable dopants within the films. It is believed that the dopants change domain-switching behaviour via the boundary charge compensation. Meanwhile, time dependence of leakage current density after time longer than lOs indicates the enhancement of the leakage cur- rent nearly in one order for the implanted film, but the current at time shorter than i s is mostly the same as that of the original film without the ionic implantation. The artificial tailoring of the antiferroelectric behaviour through H+ implantation in ferroelectric thin films is finally proven to be achievable for the device application of high-density charge storage. 相似文献
4.
P. Verardi M. Dinescu F. Craciun R. Dinu M.F. Ciobanu 《Applied Physics A: Materials Science & Processing》1999,69(7):S837-S839
Oriented crystalline Pb(ZrxTi1-x)O3 (x=0.53) (PZT) thin films were deposited on metallized glass substrates by pulsed laser deposition (1060-nm wavelength Nd:YAG laser light, 10-ns pulse duration, 10-Hz repetition rate, 0.35-J/pulse and 25-J/cm2 laser fluence), from a commercial target at substrate temperatures in the range 380-400 °C. Thin films of 1-3 7m were grown on Au(111)/ Pt/NiCr/glass substrates with a rate of about 1 Å/pulse on an area of 1 cm2. The deposited PZT films with perovskite structure were oriented along the (111) direction, as was revealed from X-ray diffraction spectra. Fourier transform infrared spectroscopy (FTIR) was performed on different PZT films so that their vibrational modes could be determined. Piezoelectric d33 coefficients up to 30 pC/N were obtained on as-deposited films. Ferroelectric hysteresis loops at 100 Hz revealed a remanent polarization of 20 7C/cm2 and a coercive field of 100 kV/cm. 相似文献
5.
Quantitative ferroelectric characterization of single submicron grains in Bi-layered perovskite thin films 总被引:1,自引:0,他引:1
C. Harnagea A. Pignolet M. Alexe D. Hesse U. Gösele 《Applied Physics A: Materials Science & Processing》2000,70(3):261-267
The local polarization state and the electromechanical properties of ferroelectric thin films can be probed via the converse piezoelectric effect using scanning force microscopy (SFM) combined with a lock-in technique. This method, denominated as piezoresponse SFM, was used to characterize at the nanoscale level ferroelectric SrBi2Ta2O9 and Bi4Ti3O12 thin films, grown by pulsed laser deposition. Two types of samples were studied: polycrystalline films, with grains having random orientations, and epitaxial films, consisting of (100)orth- or (110)orth-oriented crystallites, 100 nm to 2 7m in lateral size, which are embedded into a (001)-oriented matrix. The ferroelectric domain structure was imaged and the piezoelectric response under different external conditions was locally measured for each type of sample. Different investigation procedures are described in order to study the ferroelectric properties via the electromechanical response. A distinct ferroelectric behavior was found for single grains of SrBi2Ta2O9 as small as 200 nm in lateral size, as well as for 1.2 7m쏿 nm crystallites of Bi4Ti3O12. By probing separately the crystallites and the matrix the investigations have demonstrated at the nanoscale level that SrBi2Ta2O9 has no spontaneous polarization along its crystallographic c-axis, whereas Bi4Ti3O12 exhibits a piezoelectric behavior along both the a- and c-directions. The electrostriction coefficients were estimated to be 3᎒-2 m4/C2 for polycrystalline SrBi2Ta2O9 and 7.7᎒-3 m4/C2 for c-orientedBi4Ti3O12. Quantitative measurements at the nanoscale level, within the experimental errors give the same values for remanent polarization and coercive field as macroscopic ferroelectric measurements performed on the same samples. 相似文献
6.
7.
New methods for fabricating highly 𘚡¢-oriented and complete 𘜏¢-textured Pb(Ta0.05Zr0.48Ti0.47)O3 (PTZT) films on Pt/TiO2/SiO2/Si(001) substrates by pulsed-laser deposition have been developed using conductive oxide La0.25Sr0.75CoO3 and SrRuO3 electrodes. The 𘚡¢-preferred orientated PTZT ferroelectric capacitor was not subjected to loss of its polarization after 1᎒10 switching cycles at an applied voltage of 5 V and a frequency of 1 MHz, and the 𘜏¢-textured PTZT film capacitor retains 94.7% of its polarization after 1.5᎒10 switching cycles at 5 V and 50 kHz. The PTZT capacitors using these conductive oxide electrodes have low leakage current dominated by Schottky field emission mechanism. 相似文献
8.
Large Storage Window in a-SiNx/nc-Si/a-SiNx Sandwiched Structure for Nanocrystalline Silicon Floating Gate Memory Application 下载免费PDF全文
An a-SiNx/nanocrystalline silicon [(nc-Si)/a-SiNx] sandwiched structure is fabricated in a plasma enhanced chemical vapour deposition (PECVD) system at low temperature (250℃). The nc-Si layer is fabricated from a hydrogen-diluted silane mixture gas by using a layer-by-layer deposition technique. Atom force microscopy measurement shows that the density of nc-Si is about 2 ×10^11 cm^-2. By the pretreatment of plasma nitridation, low density of interface states and high-quality interface between the Si substrate and a-SiNs insulator layer are obtained. The density of interface state at the midgap is calculated to be 1 ×10^10 cm^-2eV^-1 from the quasistatic and high frequency C - V data. The charging and discharging property of nc-Si quantum dots is studied by capacitance-voltage (C- V) measurement at room temperature. An ultra-large hysteresis is observed in the C - V characteristics, which is attributed to storage of the electrons and holes into the nc-Si dots. The long-term charge-loss process is studied and ascribed to low density of interface states at SiNx/Si substrate. 相似文献
9.
Effect of Annealing on Ferroelectric Properties of Nanometre BaTiO3 Ceramics Prepared by High Pressure Sintering Method 下载免费PDF全文
Dense nanocrystalline BaTiO3 ceramics with a grain size of 5Onto are prepared under 6 GPa at 1273K using a high pressure sintering method. The sintered bulk is uniform and the relative density is above 97%. We anneal the ceramic samples in oxygen with various temperatures and for the annealing, several broadened peaks can be observed at different times without apparent grain growth. After about 378K( by dielectric measurements. However, these peaks are very different from those of coarser-grained ceramics. It is indicated that both the elimination of oxygen vacancies and the release of residual stresses caused by high pressure greatly improve the overall ferroelectric properties of BaTiO3 ceramics. The observation of nearly linear polarization hysteresis loop after anneal provides the solid evidence of ferroelectricity in these nano-sized BaTiO3 ceramics. It is believed that the absence of 90° domains and the existence of poor-permittivity nonferroelectric grain boundaries contribute to the slim loop. 相似文献
10.
J.-M. Liu W.M. Wang Z.G. Liu H.L. Chan C.L. Choy 《Applied Physics A: Materials Science & Processing》2002,75(4):507-514
A Monte Carlo algorithm for dynamic hysteresis simulation in ferroelectric spin systems is developed based on a DIFFOUR model
in which the local spontaneous polarization is defined by the double-well potential energy and the nearest-neighbor spin interaction
as well as an external electrical field of variable amplitude and frequency. A direct measurement of the hysteresis loop for
ferroelectric Pb(Zr0.52Ti0.48)O3 thin film capacitors using the Sawyer–Tower technique is performed. Significant dependence of the hysteresis shape and pattern
on the external field is revealed. Direct imaging of the simulated domain pattern indicates serious suppression of the domain
switching over the high-frequency range. The evaluated scaling relations from the simulation for remanence, coercivity, and
the area of the hysteresis over the low-frequency range are supported by theoretical predictions and experiments, but the
high-frequency scaling behaviors as derived are different from one and another.
Received: 23 January 2001 / Accepted: 17 August 2001 / Published online: 20 December 2001 相似文献
11.
研究了Pb[(Zr052Ti048)095(Mn1/3Nb2/3)005]O3 (PMnN_PZT) 铁电陶瓷电滞回线的温度和频率响应,结果显示在高频和室温条件下测试铁电特性时,电滞回线呈现“束腰”形状,而不是通常所看到的方形回线 . 在低频和高温条件下测试时才能观察到正常的方形回线,同时,诸如矫顽场、极化强度、 内偏场这些重要的铁电参数也会随频率和温度发生显著的变化. 剩余极化强度随频率和温度 的大幅增长表明“束腰” 电滞回线有可能是由于缺陷偶极子引起的. 电滞回线形状与温度 和频率存在较强的相关性说明缺陷偶极子存在一特征弛豫时间,缺陷偶极子反转响应速度由 此弛豫时间决定.
关键词:
电滞回线
氧空位
频率响应
温度响应 相似文献
12.
13.
Magnetization curves of untreated and laser scribed GO FeSi steels were measured for 19 different frequencies from 0.05 to 500 Hz and for four polarizations from 1.4 to 1.7 T. From hysteresis loops, hysteresis losses were separated and frequency-dependent anomaly factors were calculated. Frequency-dependent anomaly factors for all measured polarizations can be very well described by an empirical equation. This behavior can be explained by the fact that an increase in polarization at a fixed magnetizing frequency corresponds to an increase of magnetizing frequency at a fixed polarization. Both an increase in frequency and an increase in polarization activate a higher number of domain walls in the magnetization process. The power losses can be described only by the frequency dependence of the anomaly factor and by the additional knowledge of hysteresis loss. 相似文献
14.
15.
Polarized Micro-Raman Study of the Temperature-Induced Phase Transition In 0.67 Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 下载免费PDF全文
Polarized Raman spectra of ferroelectric relaxor 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (0.67PMN-0.33PT) single crystal are systematically investigated in a wide temperature range from -196 to 600℃ by micro-Raman scattering technique. The results clearly reveal that there are two structural phase transitions in such composite ferroelectric relaxor: the rhombohedral-tetragonal (R- T) phase transition and the tetragonal-cubic (T- C) phase transition. The former occurs at about TR-T =34℃, corresponding to the vanishing of the soft A1 mode at 106cm^-1 recorded in the parallel polarization. The latter appears at about TT-C = 144℃, which can be verified with the vanishing of mode at 780cm^-1 measured in the crossed polarization. 相似文献
16.
本文采用DAC(金刚石压砧高压腔)装置,对氧化镍进行了静水压、非静水压、电导率测量等系统高压实验,获取了氧化镍等温压缩、高压相变及电导率压力效应的新结果,并在实验数据的基础上,对其高压相变与电性及磁性变化关系及体弹性模量作了分析讨论。 相似文献
17.
Ruthenium (Ru) nanocrystals (NCs) embedded in SiO2 gate stacks are formed by rapid thermal annealing for the whole gate stacks and embedded in the memory structure, which is compatible with conventional CMOS technology. The devices exhibit a substantial and clockwise hysteresis in capacitance-voltage measurement. The Ru NCs exhibit high density (2 × 10^12cm^-2), small size (2-4 nm) and good uniformity both in spatial distribution and morphology. The charging and long-term retention performances are explained by the Coulomb Blockade phenomena and the asymmetric electron tunnel barrier between the Ru NCs and the Si substrate, respectively. 相似文献
18.
S. Tirumala S.B. Desu A. Rastogi 《Applied Physics A: Materials Science & Processing》2000,70(3):253-259
Crystallization of SrBi2Ta2O9 (SBT) thin films was studied as a function of viscosity of bismuth precursor and baking temperature, in order to fabricate capacitors with improved ferroelectric properties. SBT thin films were deposited on to Pt substrates using a chemical solution deposition (CSD) technique. Post-deposition anneal at 750 °C for 1 h in oxygen atmosphere revealed a significant influence of baking temperature and the viscosity of bismuth precursor on the microstructure and the ferroelectric properties of SBT thin films. A high baking temperature (350 °C) and a low viscosity of bismuth precursor (8 cp) yielded larger amounts of Bi2O3 secondary phase, smaller SBT grains (104 nm), and lower remanent polarization (Pr=2.0 7c/cm2). Additionally, these films exhibited a very high rate of ageing (>45% reduction in Pr after 7 days). A modified CSD process is suggested, which could suppress the formation of Bi2O3 secondary phase. Films fabricated using modified CSD technique exhibited a much larger grain size of 165 nm, higher Pr of 7.2 7c/cm2, and significantly improved ageing characteristics (<1% reduction in Pr after 7 days). A qualitative model to describe the ageing in SBT-based capacitors is also suggested. 相似文献
19.
The dynamic properties and the domain structure of an epitaxial (111) garnet ferrite film with perpendicular anisotropy have been considered in a harmonic magnetic field with an amplitude in the range 0–170 Oe and a frequency in the range 0.2–7.0 kHz. A direct correspondence between the obtained images of dynamic domain structures and particular sections of the hysteresis loops is set up. It has been established that variations in the parameters of the magnetic field lead to qualitative changes observed in the domain structure and, correspondingly, in the shape and area of the hysteresis loops. 相似文献
20.
M. Algueró A. Kholkin M.L. Calzada L. Pardo 《Applied Physics A: Materials Science & Processing》2000,71(2):195-202
Pb0.88La0.08TiO3 films were processed on Si-based substrates by a diol-based sol-gel route from solutions with variable content of PbO excess. Crystallisation was performed at heating rates of 10 °C min-1 and higher than 500 °C min-1 (rapid heating). The pyroelectric coefficient was measured after poling the samples by two methods: applying a sinusoidal wave and applying a train of square pulses, with the latter showing a higher poling efficiency. The piezoelectric d33 coefficient was determined by double-beam interferometry. Strain vs. field measurements provided evidence of 90° domain orientation in these films. Those crystallised at 10 °C min-1 showed the highest functional properties (%=1.7᎒-2 7C cm-2 K-1 and d33=57 pm V-1). This is a consequence of the higher stability of the 90° domains oriented during poling, caused by the lower tensile stress arising during preparation. The voltage responsivity of these films also benefited from the lower permittivity arising from their higher porosity. These films are good candidates for applications in infrared detectors and microelectromechanical devices. 相似文献