共查询到20条相似文献,搜索用时 0 毫秒
1.
D. Y. Wang Y. Wang J. Y. Dai H. L. W. Chan C. L. Choy 《Journal of Electroceramics》2006,16(4):587-591
Heteroepitaxial Ba0.7Sr0.3TiO3 thin films were grown on (LaAlO3)0.3(Sr2AlTaO6)0.35 (001) (LSAT) and SrTiO3 (001) (STO) single crystal substrates using pulsed laser deposition (PLD). X-ray diffraction characterization revealed a
good crystallinity and a pure perovskite structure for films grown on both LSAT and STO substrates. The in-plane ferroelectric
and dielectric properties of the films were studied using interdigital electrodes (IDE). The film grown on LSAT substrate
exhibited an enhanced in-plane ferroelectricity, including a well-defined P-E hysteresis loop with the remnant polarization
P
r
= 10.5 μC/cm2 and a butterfly-shaped C-V curve. Nevertheless, only a slim hysteresis loop was observed in the film grown on STO substrate. Curie temperature T
c
of the film grown on LSAT substrate was found to be ∼105∘C, which is nearly 70∘C higher than that of the bulk Ba0.7Sr0.3TiO3 ceramics. T
c
of the film grown on STO substrate has almost no change compared to the bulk Ba0.7Sr0.3TiO3 ceramics. The dielectric tunabilities were found to be 64% and 52% at 1 MHz for the films grown on LSAT and STO substrates,
respectively. 相似文献
2.
《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
3.
Abdelkader Outzourhit Ali Naziripour John U. Trefny Tomoko Kito Baki Yarar Robert Yandrofski 《组合铁电体》2013,141(4):227-241
Abstract Ba1?x Sr x TiO3 thin film capacitors have been successfully prepared using rf-sputtering and a metal organic deposition (MOD) method. The structure, microstructure and composition of the BSTO films are presented. Films grown on lanthanum aluminate LAO(100) showed c-axis preferred growth orientation. Broad paraelectric-to-ferroelectric transitions were observed in films prepared by both methods. The tunability of the capacitance by means of an appplied electric field is examined using various capacitor geometries. A decrease in the capacitance exceeding 75% at 77 K was obtained from the MOD deposited films under an electric field strength of 0.3 MV/cm. On the other hand, the tunability of the capacitance in the rf-sputtered films ranged from 5 to 10% at 77 K and at 20 kV/cm, while it exceeds 50% in some films. The results are compared with the predictions of Devonshire's phenomenological theory. 相似文献
4.
Abstract A comparison of the ac conductivity of laser ablated (Ba, Sr)TiO3 thin films was made for films grown at different substrate temperatures. The ac conductivity was studied as a function of frequency and ambient temperature ranging from room temperature to 460°C. Conductivity results from ac and dc measurements were compared in their an respective Arrhenius plots revealing interesting coincidences. The value of the activation energies computed from the Arrhenius plot of à ac with 1000/T ranged from 0.97 to 1.3 eV in the high temperature region to 0.36 to 0.54 eV in the low temperature region for different samples. The activation energies obtained from pure dc measurement for fields greater than 100 kV/cm across the samples were in the range of 1.06 to 1.32 eV for different samples. The similarity in results suggests a common origin in the de conduction process in the concerned temperature range and was attributed to ionic conduction resulting from oxygen vacancy motion which has been observed to be significant at high temperatures and high fields. For high temperature grown samples the value of activation energy computed from the Arrhenius plots was comparatively less than those grown at lower substrate temperatures. The difference was attributed to the microstructure and the effect of grain boundaries on the motion of oxygen vacancies leading to the conduction process. 相似文献
5.
B. J. Kim S. Baik Y. Poplavko Y. Prokopenko J. Y. Lim B. M. Kim 《Integrated ferroelectrics》2013,141(1-4):207-214
Abstract A tunable phase shifter was fabricated with epitaxial Ba0.5Sr0.5TiO3 (BST) thin film and gold coplanar waveguide. BST thin film of the thickness ~0.5 μm was deposited by laser ablation on the MgO(OOl) single crystalline substrate. Gold electrode of the thickness ~2 μm was prepared by the sequence of thermal evaporation, electroplating, and wet etching. Epitaxial quality of the BST thin film was confirmed by X-ray diffraction. The microwave performance of phase shifter was measured at room temperature in the frequency range of 8–12 GHz, and with applied bias voltage of up to 30 V. Effect of Mn dopant in the epitaxial films was also considered. 相似文献
6.
Abstract The leakage current and dielectric properties of (Ba0.5Sr0.5)TiO3(BST) thin films prepared by pulsed laser deposition (PLD) were investigated. It was found that leakage currents for positive bias voltage were higher than that for negative bias voltage, which was attributed to the lattice mismatch between bottom Pt electrode and BST thin film. The time-dependent breakdown process under positive voltage was observed, which was interpreted as the increase of the internal electric field in the film near the bottom electrode. However, the internal electric field can be decreased and eventually recovered by applying negative bias voltage. It was found that internal electric field near the interface can influence the capacitance of the BST thin film capacitor. An explanation for the thickness effect of BST thin films was given. 相似文献
7.
Hyun-Suk Kim Tae-Seon Hyun Ho-Gi Kim Tae-Soon Yun Jong-Chul Lee Il-Doo Kim 《Journal of Electroceramics》2007,18(3-4):305-309
(100) epitaxial Ba0.6Sr0.4TiO3 (BST) thin films were grown on Si substrates using a 9 nm thick SrO buffer layer. The phase shifter fabricated on BST films
grown on a SrO buffered Si substrate showed a larger figure of merit (FOM) of 24.7°/dB as a result of improving the phase
tuning while retaining an appropriate insertion loss compared to that (15.3°/dB) for the BST/MgO structure. This work demonstrates
that a thin SrO buffer layer plays an important role in the successful integration of BST-based microwave tunable devices
onto Si wafers. 相似文献
8.
Hyun-Suk Kim Il-Doo Kim Ki-Byoung Kim Tae-Soon Yun Jong-Chul Lee Harry L. Tuller Won-Youl Choi Ho-Gi Kim 《Journal of Electroceramics》2006,17(2-4):421-425
We report on high tunablity of Ba0.6Sr0.4TiO3 (BST) thin films realized through the use of atomic layer deposited TiO2 films as a microwave buffer layer between BST and a high resistivity (HR) Si substrate. Coplanar waveguide (CPW) meander-line
phase shifters using BST/TiO2/HR-Si and BST/MgO structures exhibited a differential phase shift of 95∘ and 24.4∘, respectively, at 15 GHz under an electric field of 10 kV/cm. The figure of merit of the phase shifters at 15 GHz was 30.6∘/dB for BST film grown on a TiO2/HR-Si substrate and 12.2∘/dB for BST film grown on a MgO single crystal substrate. These results constitute significant progress in integrating BST
films with conventional silicon technology. 相似文献
9.
《组合铁电体》2013,141(1):1107-1114
In this paper, in order to obtain a large differential phase shift with a little change in applied voltage, a ferroelectric reflective load circuit has been designed on top of barium strontium titanate (Ba,Sr)TiO3 [BST] thin film. The design of the ferroelectric reflection-type phase shifter is based on a reflection theory of terminating circuit, which has a reflection-type analogue phase shifter with two ports terminated in symmetric phase-controllable reflective networks. To achieve large amounts of phase shift in low bias-voltage range, the effects of change of capacitance and transmission line connected with two coupled ports of a 3-dB 90° branch-line hybrid coupler have been investigated. A large phase shift with a small capacitance change in the parallel terminating circuit has been demonstrated in the paper. 相似文献
10.
Yu Liu Baki Acikeia Amit S. Nagra Troy R. Taylor Peter J. Hansen James S. Speck 《Integrated ferroelectrics》2013,141(1-4):313-320
Abstract Sol-gel solutions were synthesized by using various alkoxides of polyhydric alcohol, carboxylate and stabilizer. Stability of modified sol-gel solution was good enough to keep its properties after at least three months although that of ordinary sol-gel solution is not good. SBT films were fabricated on Pt(200nm)/Ti(20nm)SiO2(500nm)/Si substrate at under 700°C by using modified sol-gel solution. Range of drying temperature was 200 to 400°C and that of RTA was 550 to 700°C. At high drying temperature, decrease of crystallinity for SBT films was observed accompanied by nucleation of Sr carbonate. On the other hand, SBT film dried at under 250°C and crystallized at 700°C shows high crystallinity of layer perovskite. SBT film derived from conventional sol-gel solution used to show strong crystal orientation of c-axis. In case of modified sol-gel solution, RTA temperature and amount of added stabilizer influenced crystal orientation of film. So it was possible that to control crystal orientation of SBT films by adjust RTA condition and amount of stabilizer. Stability of sol-gel solution and property of SBT films were influenced by component of solvent, electric properties of SBT films especially I-V property were improved. Using low temperature deposition process at 650°C, SBT films derived from modified sol-gel solution show superior ferroelectric properties to SBT thin films derived from conventional MOD solution. 相似文献
11.
The phenomena of dc electrical degradation of (Ba/sub 0.5/Sr/sub 0.5/)TiO/sub 3/ thin films was studied. From our experimental and analytical results of current versus voltage (I-V) characteristics, it was shown that the degraded devices exhibited analogous leakage behaviors with the devices which have thin intercalated (Ba/sub 0.5/Sr/sub 0.5/)TiO/sub 3/ layers with intentionally introduced oxygen vacancies between cathodes and thick (Ba/sub 0.5/Sr/sub 0.5/)TiO/sub 3/ layers without intentionally introduced oxygen vacancies. This could be explained by assuming that oxygen vacancies accumulate at the interfaces between the cathodes and the (Ba/sub 0.5/Sr/sub 0.5/)TiO/sub 3/ films after fatigue. 相似文献
12.
Mi-Hwa Lim Hyun-Suk Kim Nan-Young Kim Ho-Gi Kim Il-Doo Kim Seung Eon Moon Min-Hwan Kwak Han-Cheol Ryu Su-Jae Lee 《Journal of Electroceramics》2004,13(1-3):239-243
Highly (100) preferred undoped and 1–5% Ni-doped Ba1–xSrxTiO3 (BST) thin films were deposited onto MgO (100) single crystal substrate at 750°C using pulsed laser deposition. BST thin film-based interdigital capacitors (IDC) were prepared by standard photolithography process. The microwave properties of BST films were measured at 10 GHz. Ni-doped BST films showed better dielectric properties by exhibiting improved dielectric Q while retaining an appropriate capacitance tuning compared to undoped BST films. 1% Ni-doped BST film showed the maximum figure of merit of 2896.1. It is suggested that 1 mol% Ni doped BST film is an effective candidate for high performance tunable device applications. 相似文献
13.
Haitao Huang Wei Qiu Ooi Kiang Tan Weiguang Zhu Li Min Zhou 《Journal of Electroceramics》2006,16(4):337-341
Nanoscaled (Ba2/3Sr1/3)Ti1 + x
O3 powders have been prepared by sol-gel technique. Their phase evolution and densification behaviors have been studied by differential
thermal analysis (DTA) and high temperature dilatometer, respectively. It is found the addition of 2 mol%-excess amount of
TiO2 lowers the activation energy required for the formation of the perovskite phase by about 130 kJ/mol and thus lowers the crystallization
temperature of BST powders. However, the excess amount of TiO2 makes the nano-powder difficult to sinter. Transmission electron microscopy reveals that a metastable nano-porous layer has
formed on the surface of TiO2-excess nanopowder and this may account for the slow densification rate. 相似文献
14.
Jaemo Im O. Auciello P. K. Baumann S. K. Streiffer D. Y. Kaufman A. R. Krauss 《Integrated ferroelectrics》2013,141(1-4):263-270
Abstract High permittivity (BaxSr1?x)Ti1+yO3+z(BST) thin films are being investigated for integration into charge storage dielectrics and electric-field tunable elements for high frequency devices. For the latter application, it is desirable to have BST capacitors with high tunability and low losses. Therefore, we investigated the use of multilayer BST thin films consisting of very low dielectric loss BST/electrode interfacial layers ((Ba+Sr)/Ti = 0.73) sandwiching a high tunability, high permittivity primary BST layer ((Ba+Sr)/Ti = 0.9). BST capacitors with multiple layers of controlled composition can be effectively produced insitu by magnetron sputter deposition, using a single stoichiometric target and controlling the layer composition by changing the total process gas (Ar+O<2) pressure. The layered BST film capacitors exhibit simultaneous low loss (tan Δ = 0.005), high tunability (76%), high charge storage energy density (34 J/cm3), low leakage, and high dielectric breakdown (>2.8 MV/cm). 相似文献
15.
WON-JEONG KIM SANG SU KIM TAE KWON SONG S. E. Moon E. K. KIM S. J. LEE 《Integrated ferroelectrics》2013,141(1):321-327
Ferroelectric (Ba,Sr)TiO3 films have been deposited on (001) MgO single crystals by a pulsed laser deposition with oxygen background while heating the substrates. Deposited BST films exhibit epitaxial growth along (001), which are confirmed by x-ray diffraction measurement. Structure of (Ba,Sr)TiO3 along in-plane and surface normal direction have been investigated and found to have a tetragonal distortion depend on the deposition conditions, such as oxygen pressure. Lattice parameter decreases with increasing oxygen pressure, and tetragonallity (c/a) changes from 1.005 to 0.997 as oxygen pressure increase. Interestingly, energy gap measured by FTIR decreases with decreasing oxygen pressure until it reach a certain oxygen pressure, then increases again with increasing oxygen pressure. Furthermore, microwave properties of devices measured by a HP 8510C vector network analyzer from 0.045–20 GHz suggest that the least distorted films exhibit a larger dielectric constant changes with dc bias field. 相似文献
16.
ABSTRACTThe influences of Y and Mn alternately doped order on the microstructures and dielectric properties of the Ba0.6Sr0.4TiO3 (BST) films were reported in this paper. The Y and Mn alternately doped BST films were designed as YBST/MnBST/… and MnBST/YBST…multilayer films orderly expressed as (Y/Mn)M and (Mn/Y)M for short, and prepared on Pt/Ti/SiO2/Si wafers by an improved sol-gel method, where Y and Mn represent yttrium doped BST layer and manganese doped BST layer, and M is cycle unit, respectively. The microstructures of the alternately doped BST films were observed by SEM and the capacitance-voltage curves at 100 kHz or 1 MHz were measured by a HP4284A LCR meter and the dielectric properties in the range of 1GHz were measured by an E4991A impedance analyzer. Compared to Y or Mn doped multilayer BST film, (Y/Mn)M and (Mn/Y)M show higher dielectric tunability and lower dielectric loss with higher dielectric constant. Moreover, (Y/Mn)M show better dielectric properties than (Mn/Y)M because (Y/Mn)M show granular microstructures independent of M, while the (Mn/Y)M show granular microstructures when M is 2 and add to a surface layer of columnar microstructures on the granular microstructures when M is 4. The related mechanisms were obtained in terms of the XRD phase structures, the cross-sectional SEM microstructures and the AFM morphologies. 相似文献
17.
《Integrated ferroelectrics》2013,141(1):1175-1184
(Ba0.7Sr0.3)TiO3 and SrTiO3 thin films were deposited on Pt electrodes in a planetary multi-wafer MOCVD reactor. The nucleation behavior and the size of the stable nuclei were investigated by different SPM techniques. Characteristic differences were observed for different deposition temperatures, i.e. a homogeneous nucleation of small BST grains on the larger Pt grains at 565°C and a dominating nucleation at the grain boundaries at 655°C. The micro structural evolution after further film growth was investigated by HRTEM and revealed randomly oriented grains (typical inplane size 10–20 nm) with a high density of twins at 565°C and (100)-oriented defect free grains of only slightly increased size at 655°C. For SrTiO3 the inplane grain size was increased, however, the (100) texture was less perfect. As the electrical properties like permittivity and also leakage current depend on film thickness the final discussions of the electrical properties are based on thickness series (5 nm–100 nm films) and evaluated within the phenomenological dead layer model. 相似文献
18.
A. I. Dedyk E. A. Nenasheva A. D. Kanareykin Ju. V. Pavlova O. V. Sinjukova S. F. Karmanenko 《Journal of Electroceramics》2006,17(2-4):433-437
The BaxSr1 − x
TiO3 ferroelectric ceramics with magnesium (BSM) and neodymium (BSN) additives were studied. Measurements were made of tunability,
dielectric losses (tan δ), leakage currents, the correlations between current-voltage I(U) and capacitance-voltage C(U) characteristics. I(U) characteristics of high quality BSM ceramics have four regions: Ohmic, where the conductivity is linear; the horizontal
region (or negative differential resistivity); the exponential dependence; and the vertical current enhancement. These BSM
samples (∼20% Mg additives) were distinguished by highest breakdown strength (more than 1000 V), low tan δ (less than 10− 3 at 1 MHz) and high tunability (up to 10% at E
max∼2 V/μm). 相似文献
19.
Y. B. Zheng S. J. Wang L. B. Kong S. Tripathy A. C. H. Huan C. K. Ong 《Journal of Electroceramics》2006,16(4):571-574
Ba0.5Sr0.5TiO3 thin films doped with different concentration of Ti, Mg and Al dopants were prepared by pulsed laser deposition technique
on LaAlO3 substrates. The crystalline properties of these doped thin films were studied using X-ray diffraction, micro-Raman scattering,
atomic force microscopy, and transmission electron microscopy. The bandgap energies of BST thin films are determined from
the transmission and absorption measurements by the ultraviolet-visible spectrophotometer. It was found out that the bandgap
energies of the doped BST thin films depend strongly on the dopant concentration. 相似文献
20.
Sang Su Kim Jun-Ki Chung In-Sung Kim Jae-Sung Song Cheol Jin Kim Won-Jeong Kim 《Journal of Electroceramics》2006,17(2-4):451-454
Thick BST films have been fabricated by a tape casting and firing method. Dielectric constants of BST films are changed from
5700 to 7000 at 1 MHz after focused beam annealing. Furthermore, surface morphologies and depth profile of chemistry have
been altered after annealing. Especially, Sr atoms diffuse out to the surface, while Ba atoms diffuse into the center. The
possibility of the surface alteration of the thick films have been clearly demonstrated in this study, which may applied for
the integration of ferroelectrics and other dielectrics and/or conductors for low cost microwave tunable devices. 相似文献