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1.
Abstract The temperature dependence of the dielectric constant (ε) of SrTiO3 films on the various dielectric substrates differs radically from ε(T) dependence for bulk single crystal. This difference may be connected with temperature dependence of mechanical stress in the film. XRD measurements suggest the high mechanical deformation (u) of STO film unit cells at room temperature. But there is no experimental data about dependence u(T) nowadays. Present work is devoted to investigation of temperature and electric field dependencies of capacitance (C(U,T), C(Q,T)) of capacitor on the structure STO film/sapphire substrate. It is shown that derivative of inverse capacitance on the temperature is not constant and has a maximum at temperature about 200 K. Position of maximum is not influenced by charge (Qi) on the capacitor. The mechanical deformations play the dominant role in the formation of maximum. The temperature behavior of macroscopic mechanical deformations in STO thin film on sapphire substrate is discussed. 相似文献
2.
《Integrated ferroelectrics》2013,141(1):1257-1264
PZT thin films are deposited on SiO2/Si substrate by metallo-organic decomposition (MOD) process, using SrTiO3 (STO) as buffer layer for textured growth. The STO layers deposited on SiO2/Si substrate by pulsed laser deposition process show (100)/(200) preferred orientation, whereas the STO buffer layer deposited on silica substrate using spin-coating technique show random orientation behavior. The use of STO as buffer layers enhanced the crystallization and the preferred orientations of the PZT films. The PZT on STO buffered SiO2/Si substrates thus obtained possess high refractive index, (n)PZT/STO = 2.1159, and are of good enough quality for optical waveguide applications. 相似文献
3.
K. Daoudi T. Tsuchiya I. Yamaguchi T. Manabe S. Mizuta T. Kumagai 《Journal of Electroceramics》2006,16(4):527-532
Epitaxial La0.7Ca0.3MnO3 (LCMO) thin films were successfully prepared by the metal-organic deposition process on various (001) single-crystal substrates:
MgO, LaAlO3 (LAO), SrTiO3 (STO), and (LaAlO3)0.3-(SrAlTaO6)0.7 (LSAT). The crystallinity and the epitaxial growth of the LCMO films were characterized by X-ray diffraction (θ − 2θ scans
and pole-figure analysis). The temperature dependence of the resistance of the LCMO/LSAT, LCMO/STO and LCMO/LAO films exhibit
typical characteristics with a transition from the paramagnetic-insulator state to the ferromagnetic-metallic state at a temperature
peak (T
p
) ranging from 258 to 270 K. However, the LCMO/MgO films exhibited a semiconducting behavior without any transition. Based
on the R(T) measurement, we calculated the temperature coefficient of resistance (TCR) for a bolometric application and we obtained
22%/K, 10.2%/K and 27.5%/K for the film grown on the LSAT, STO and LAO substrates, respectively. This difference in the TCR
properties is related to the strain induced by the lattice mismatch between LCMO and the different substrates. 相似文献
4.
ABSTRACT Ferroelectric properties of BiFeO3 (BFO) thin films epitaxially grown on SrRuO3 (SRO)/(001)SrTiO3 (STO) structure were investigated. First, bottom SRO electrodes were deposited on STO substrates by metalorganic chemical vapor deposition (MOCVD) or by sputtering. Then, BFO thin films were deposited on SRO/STO structures by chemical solution deposition. X-ray diffraction analysis showed that the SRO films deposited by both methods grew epitaxially on STO substrates as a single phase perovskite structure, but the out-of-plane lattice parameters of SRO were different, that is, they were 0.396 nm in MOCVD and 0.399 nm in sputtering. The leakage current densities were higher than 1 A/cm2 at room temperature in BFO films on both MOCVD-and sputtered-SRO, but the current density in the film on sputtered SRO decreased to 2 × 10?4 A/cm2 at 80 K. The remanent polarization of approximately 50 μC/cm2 was observed at 80 K in the BFO thin film on sputtered-SRO/STO. 相似文献
5.
Abstract High quality Ba0.4Sr0.6TiO3 and SrTiO3 films were grown by Pulsed Laser Deposition on single crystal LaAlO3 and MgO substrates. Temperature dependencies of the dielectric constant and loss tangent of the films were studied using planar interdigitated test capacitors with various electrode geometries. The temperature where the maximum or “peak” capacitance occurs (Tp and referred to as the “peak temperature”) is found to depend on the electrode geometry in these films. As much as 40 K difference in Tp was observed between the STO test capacitors with 5 μm and 40 μm gaps between electrodes. Interface built-in electric field and metal-ferroelectric thermal mismatch strain are considered as possible explanation of the effect of electrode geometry on peak temperature of the capacitors. 相似文献
6.
ABSTRACT Dielectric permittivity of 150 nm mean grain size Pb(Mn1/3Nb2/3)O3 (PMN) nanopowder has been investigated by dielectric spectroscopy in the 20 Hz–1 MHz frequency range and 100 K–400 K temperature range. The broad and diffused dielectric dispersion has been observed, but the dispersion region and the maximum of the real part of dielectric permittivity is shifted to lower temperatures compare to PMN single crystal and ceramics. The mean relaxation time, obtained from fits of the frequency dependences of the dielectric permittivity with Cole-Cole formula, changes according to the Vogel-Fulcher law with the freezing temperature T 0 = 88 K which is much lower than in bulk PMN materials. 相似文献
7.
Mona P. Moret Marijn A.C. Devillers Andy R.A. Zauner Edwin Aret Paul R. Hageman Poul K. Larsen 《Integrated ferroelectrics》2013,141(1-4):265-274
Abstract PbZrxTi1-xO3 (PZT) thin films were grown on 6” platinized silicon substrates (Pt / Si) and SrTiO3 (STO) crystals by Metal-Organic Chemical Vapor Deposition (MOCVD) as a function of the Zr / (Zr+Ti) ratio in the gas phase. Morphology, optical properties, and crystal structure were investigated by scanning electron microscopy, atomic force microscopy, ellipsometry, and X-ray diffraction. The morphology, structure, and optical properties of the polycrystalline and epitaxial films were compared. The determination of the refractive index by ellipsometry (from 550 nm to 2000 nm) was not sensible for the films grown on (Pt / Si) but successful for the films grown on SrTiO3. 相似文献
8.
F. JOMNI H. OUAJJI A. SYLVESTRE J. GUILLAN E. DEFAŸ C. DUBARRY 《Integrated ferroelectrics》2013,141(1):228-237
ABSTRACT Thin film capacitors with SrTiO3 (STO) as dielectric and Pt as electrode material have been prepared by ion beam sputtering. The as-deposited film is amorphous and exhibits a crystallization temperature around 321°C as proved by X-ray diffraction. The effect of post annealing on the crystalline quality of the films was systematically studied by x-ray diffraction and Atomic Force microscopy (AFM). The temperature and frequency dependent dielectric properties were measured from 30°C to 200°C and 0.01 Hz to 105 Hz, respectively. The influence of the microstructure of SrTiO3 thin films on their electrical properties was investigated through an extensive characterization. The electrical properties of SrTiO3 films appear to be strongly depending on the annealing temperatures. The capacitance voltage (C-V) characteristics reveal an improvement of capacitance density with increasing the annealing temperature. 相似文献
9.
Abstract SrTiO3 films with thickness ranging from 25nn to 2.5μm were grown on LaAlO3 substrates with SrRuO3 electrode layers. Measurements of the dielectric properties were performed over a range of temperatures The dielectric loss depends strongly on the thickness, but differently above and below T ~ 80 K. Our result suggests that, in the high temperature regime, the interfacial dead layer effect dommates while, in the low temperature regime, the losses related to the structural phase transition and quantum fluctuations are important. The contribution to the interfacial potential from Schottky barriers was investigated for different electrode materials. Preliminary results of this study suggest that the continued dielectric nonlinearity of the thin films at high temperatures (above T ~ 80 K) complicates the analysis of the Schottky barrier height measurements. 相似文献
10.
《组合铁电体》2013,141(1):1327-1335
BaTiO3 (BTO)/SrTiO3 (STO) artificial lattices have been deposited on (La,Sr)CoO3/MgO (100) substrate by pulsed laser deposition (PLD). Strain manipulation in the oxide artificial lattice was carried out by varying stacking sequence and period of BTO and STO layers with layer-by-layer growth technique. A wide variation of the lattice distortion for both BTO and STO layers has been obtained from this strain manipulation. The dielectric constant of the BTO and STO lattices was sensitively influenced by the lattice distortion. Moreover, it is found that there exist a certain degree of lattice distortion of the strained BTO and STO lattices leading to a maximum value of their own dielectric constant of the BTO and STO lattices. Consequently, an appropriate combination of stacking period and sequence (resulting in a specific lattice distortion) led to the large dielectric constant (1230) and extremely large tunability (94%) in the BTO/STO oxide artificial lattice. 相似文献
11.
Abstract One of the critical design aspects in ferroelectric tunable microstrip filters is choosing the right bias configuration, for large tunability as well as to maintain the filter's passband characteristics. This work is based on strontium titanate (STO) ferroelectric thin-film based tunable microstrip filters for cryogenic temperature applications. Large tunability factors have been demonstrated in YBCO/STO/LAO two-layered microstrip filters when operated at or below 77 K. The effect of the dc electric field (primarily responsible for tuning) and critical design parameters such as the insertion loss, frequency tunability, return loss, and bandwidth of superconductor/ferroelectric/dielectric microstrip tunable K-band microwave filters is discussed in this work. 相似文献
12.
《Integrated ferroelectrics》2013,141(1):1305-1314
Compositionally graded (Bax,Sr1 ? x)TiO3 [BST] ferroelectric thin films have been received much attention in graded ferroelectric devices due to their unique properties, such as large pyroelectric coefficients, large polarization offset and small temperature coefficient of dielectric constant for microwave tunable devices. Compositionally graded BST thin films were deposited epitaxially on LaAlO3 [LAO] and Nb-doped SrTiO3 [STO:Nb] substrates by pulsed laser deposition. The planar and parallel dielectric properties of compositionally graded BST epitaxial thin films ware investigated in the frequency ranges of 100 Hz ~ 1 MHz as a function of the direction of the composition gradient with respect to the substrate at room temperature. The dielectric properties of the graded BST films depended strongly on the direction of the composition gradient with respect to the substrate. The graded ST → BT films grown on LAO and STO:Nb substrates exhibited a excellent dielectric properties than the graded BT → ST films. 相似文献
13.
The focused ion beam microscope (FIB) has been used to fabricate thin parallel-sided ferroelectric capacitors from single crystals of BaTiO3 and SrTiO3. A series of nano-sized capacitors ranging in thickness from ~660 nm to ~300 nm were made. Cross-sectional high resolution transmission electron microscopy (HRTEM) revealed that during capacitor fabrication, the FIB rendered around 20 nm of dielectric at the electrode-dielectric interface amorphous, associated with local gallium impregnation. Such a region would act electrically in series with the single crystal and would presumably have a considerable negative influence on the dielectric properties. However, thermal annealing prior to gold electrodes deposition was found to fully recover the single crystal capacitors and homogenise the gallium profile. The dielectric testing of the STO ultra-thin single crystal capacitors was performed yielding a room temperature dielectric constant of ~300, as is the case in bulk. Therefore, there was no evidence of a collapse in dielectric constant associated with thin film dimensions. 相似文献
14.
《Integrated ferroelectrics》2013,141(1):915-922
Ba(Mg1/3Ta2/3)O3 (BMT) microwave dielectric thin films were successfully synthesized by a modified pulsed laser deposition (PLD) process, which includes low temperature (200°C) deposition and high temperature (>500°C) annealing. Crystalline structured BMT thin films were obtained when the PLD-deposited films were post-annealed at a temperature higher than 500°C in oxygen atmosphere. The characteristics of BMT thin film, including crystallinity, grain size, film roughness, and dielectric properties were improved with annealing temperature, achieving dielectric constant K = 23.5 and dissipation factor tan δ = 0.015 (at 1 MHz) for the 800°C-annealed films. 相似文献
15.
ABSTRACT BaTiO3 films were deposited by the direct vapor deposition (DVD) technique to prepare thin dielectric layers for multilayer ceramic chip capacitors (MLCCs). The BaTiO3 films were successfully prepared by co-evaporation of the BaTiO3 ceramic and Ti metal source. The films deposited at room temperature and 600°C were amorphous and crystalline phases, respectively. The intensity of (110) and (111) peaks increased as Ba/Ti ratios were close to stoichiometric composition. BaTiO3 films deposited with e-beam power of 700 W showed the deposition rate of 33 nm/min. The dielectric constant and dissipation factor of BaTiO3 films measured at 1 kHz were 150~ 180 and 2~ 5%, respectively. The capacitance decreased with increasing the temperature and varied only between 787pF and 752pF in the temperature range 15~ 125°C. 相似文献
16.
Room temperature and 77K dielectric properties of acetate-derived PZT,PLZT, PSZT and PBZT thin films
Gene H. Haertling 《Integrated ferroelectrics》2013,141(1-4):257-266
Abstract Ferroelectric thin films in the PZT, PLZT, PBZT (lead barium zirconate titanate) and PSZT (lead stannate zirconate titanate) compositional systems were prepared from as-received acetate precursors. Multiple-layer thin films were fabricated via a spin coating technique and sintered at 650 – 700°C for two to three minutes per layer, yielding an overall thickness of 0.45um. The dielectric and ferroelectric hysteresis loop properties of these films were measured at room temperature and 77K. The results show that the thin films experience a substantial loss (-80% avg.) in dielectric permittivity at 77K and a significant increase in PR, Ec and electrical breakdown strength. The phase transformation trends on cooling from room temperature to 77K were from SFE (slim-loop FE)-to-FE and AFE-to-FE. Compositions in these systems show promise for potential low temperature applications. 相似文献
17.
Abstract Dielectric properties and tunability of Ba0.60Sr0.40TiO3 (BST) and BaZr0.25Ti0.75O3 (BZT) thick films and bulk ceramics have been investigated as a function of temperature (90 K - 320 K) in the kHz region. Thick films show compared to bulk ceramics low permittivity and a very broad ferroelectric phase transition which leads to low temperature dependence of tunability. Tunability of 30% can be achieved with an external field of 2 kV/mm. Measurements in the microwave region adumbrate that the dielectric losses of BZT are about three times higher than that of BST thick films. 相似文献
18.
19.
Abstract The process of the production of LiNbO3 thin films by sputtering onto cold silicon substrates followed by heat treatment was investigated. Composition, structure and physical properties of the films were investigated using light refractive indices, θ ?2θ X-ray diffraction and scanning electron microscopy, capacitance and dielectric constant measurements. The amount of the crystalline phase of the stoichiometric composition was found to be about 90%. The refractive index (λ = 632.8 nm) and the dielectric constant of the best samples were as high as 2.28 and 40, respectively. Insulating properties of this film structure were studied by SEM using e-beam sample charging. The potential images of the film structure provided evidence that current leakage takes place in the boundary areas between the crystallite and noncrystallite phases. 相似文献
20.
Abstract The dielectric and ferroelectric properties for Au/Pb(Zr,Ti)O3/YBa2Cu3O7?x heterostructures at low temperatures are reported. The fatigue behavior and the ferroelectric switching effect for the structures are also investigated. The PZT/YBCO thin film heterostructures were deposited on MgO(100) substrates by laser ablation. The ferroelectric and dielectric properties and optical response of the oriented PZT films with different thicknesses have been studied over the temperature range from 20 K to 300 K. The dielectric loss of the structure was found to decrease by an order of magnitude when the YBCO bottom electrode became superconducting. A very low fatigue rate of the structure has also been obtained below T c of YBCO layer. 相似文献