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1.
K. K. Deb T. Tamagawa Y. Di G. Gui B. L. Halpern J. J. Schmitt 《Journal of Electronic Materials》2001,30(2):89-93
In this work, we grew lead titanate (PbTiO3) and La-modified PbTiO3 thin films on platinized silicon (Si(100)) substrates under controlled substrate temperature and ambient by a modified jet-vapor
deposition (JVD) process described in this paper. The x-ray diffraction patterns obtained from these films showed a single-phase
perovskite structure. We examined locally homogeneity and thickness of these films through the comparative use of laser Raman
spectroscopy. We also collected Raman and x-ray data on pure PbTiO3, as well as prepared lead zirconate titanate (PZT) (54/46), and PZT (50/50) films using the JVD process. This paper discusses
the temperature variations of the pyroelectric and dielectric properties of three compositions of La-modified PbTiO3 films containing 5.2% to 15% of La, respectively, with a view toward studying the effect of La in place of Pb on these electrical
properties. We detected significant pyroelectric currents on all three La-modified PbTiO3 films before performing poling treatments, and observed pyroelectric coefficeints as high as 84 nC/cm2·°C in the poled La-doped PbTiO3 films containing 5.2% La. The pyroelectric coefficient and dielectric constant varied significantly with La content. We compared
the calculated figures of merit, which were based on the measured physical properties, with pure PbTiO3 as well as PZT and lead lanthanide zirconate titanate (PLZT) films. These properties just described illustrate that these
films would be suitable for IR detectors. 相似文献
2.
The ferroelectric properties of Nb-doped PZT thin films prepared by a sol-gel method were evaluated relative to memory device
application requirements. Within the range of 0 to 4 mol %, Nb-doping of PZT compositions near the morphotropic phase boundary
region (i.e. PZT 53/47) enhanced overall ferroelectric properties by reducing the te-tragonal distortion of the unit cell. A 4 mol % Nb-doped
PZT 53/47 thin film (0.26 μm) had a coercivity of 8 V/ μm, a remanence ratio of 0.54, a switchable polarization of 45 μC/cm2, and a specific resistivity of 3 x 109 Ω-cm. Nb-doping levels in excess of 5 mol had a detrimental effect on the resulting thin film ferroelectric properties. X-ray
diffraction (XRD) analysis of highly doped films showed development of a significant PbO phase accompanied by diffraction
line broadening of the perovskite phase. As such, it was postulated that the creation of excessive lead vacancies in the PNZT
lattice resulted in PbO accumulation at the grain boundaries which impeded grain growth, and hence, adversely affected ferroelectric
switching performance. The fatigue performance of the sol-gel derived thin film capacitor system was a function of switching
voltage. At switching fields sufficient to saturate the polarization, the endurance of the thin film capacitor was greater
than 109 cycles. Cycling with lower fields reduced endurance values, but in all cases, the switchable polarization decreased linearly
with the logarithm of cycles. Nb-doping did not have a significant effect on the fatigue performance. 相似文献
3.
F. Chu Q. X. Jia G. Landrum X. D. Wu M. Hawley T. E. Mitchell 《Journal of Electronic Materials》1996,25(11):1754-1759
Conductive SrRuO3 thin films have been deposited using pulsed laser deposition on LaA103 substrates at different substrate temperatures. Structural and microstructural properties of the SrRuO3/LaAlO3 system have been studied using x-ray diffraction, scanning electron microscopy, and scanning tunneling microscopy. Electrical
properties of SrRuO3 thin films have been measured. It was found that the film deposited at 250°C is amorphous, showing semiconductor-like temperature
dependence of electrical conductivity. The film deposited at 425°C is crystalline with very fine grain size (100∼200?), showing
both metallic and semiconductor-like temperature dependence of electrical conductivity in different temperature regions. The
film deposited at 775°C shows a resistivity of 280 μΩ.cm at room temperature and a residual resistivity ratio of 8.4. Optimized
deposition conditions to grow SrRuO3 thin films on LaA103 substrates have been found. Possible engineering applications of SrRuO3 thin films deposited at different temperatures are discussed. Bulk and surface electronic structures of SrRuO3 are calculated using a semi-empirical valence electron linear combination of atomic orbitals approach. The theoretical calculation
results are employed to understand the electrical properties of SrRuO3 thin films. 相似文献
4.
M. Lorenz H. Hochmuth M. Grundmann E. Gaganidze J. Halbritter 《Solid-state electronics》2003,47(12):2183
Ca doping of YBa2Cu3O7−δ (YBCO) is well known to enhance the critical current density in large-angle grain boundaries for example of bicrystals. However, up to now no data are available on microwave properties of epitaxial Ca-doped YBa2Cu3O7−δ thin films on r-plane sapphire with CeO2 buffer layer.Therefore, first results are presented for large-area pulsed laser deposition (PLD) grown CaxY1−xBa2Cu3O7−δ films on 3-in. diameter sapphire wafers. The PLD process is optimised for undoped YBCO thin films and shows high reproducibility for YBCO. The microwave surface resistance Rs at 8.5 GHz of Ca-doped YBCO (x=0.1) thin films shows clear reduction (up to 20%) with respect to that of YBCO for temperatures from about 20–50 K. In addition, microwave surface resistance Rs of Ca-doped YBCO is lower than that of YBCO even for enhanced microwave surface magnetic field up to about 20 mT for temperatures 20 and 40 K. 相似文献
5.
介绍了课题组在铁电薄膜的制备、特性研究以及非制冷红外探测技术方面的研究结果。研究获得了几种控制铁电薄膜微结构(如晶粒尺寸、晶粒形状、Ba1-xSrxTiO3(BST)和PbZrxTi1-xO3 (PZT)铁电薄膜的择优取向生长等)的新技术;研制出具有高度自极化特性的0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMNT)弛豫铁电薄膜;探索了一种具有将红外转化为可见光机制的新型光读出方式;发明了PZT薄膜的低温(400 °C)生长方法。此外,还介绍了256×1线列铁电薄膜非制冷红外探测器的研制及部分成像结果。 相似文献
6.
Ferroelectric PbTiO3 thin films were deposited on bare silicon and Pt/SiO2/Si substrates by metalorganic chemical vapor deposition in a temperature range from 270 to 550°C. The deposition of a single
phase PbTiO3 thin film did not occur on bare silicon substrates. Instead a double layer of lead-silicate and PbTiO3 was formed owing to a serious diffusion of lead and oxygen ions into silicon substrates. But on Pt/SiO2/Si substrates, a single phase PbTiO3 oriented parallel to a-and c-axis was grown at a substrate temperature as low as 350°C even without a high temperature post-annealing.
To get an optimal film, a precise control of input gas composition and also a deposition in a low temperature range from 350
to 400°C are necessary. 相似文献
7.
A. C. Westerheim P. C. Mcintyre S. N. Basu D. Bhatt L. S. Yu-Jahnes Alfredo C. Anderson M. J. Cima 《Journal of Electronic Materials》1993,22(8):1113-1120
The surface morphology and microstructure of in situ and ex situ derived YBa2Cu3O7−x (YBCO) thin films have been investigated. In situ films were deposited by single-target off-axis sputtering and three-target
co-sputtering. Ex situ films were derived by metalorganic deposition (MOD) of trifluoroacetate precursors. Surface defects
resulting from mixed a-axis and c-axis orientation as well as secondary phases have been identified in these films. Despite
these defects, films with excellent electrical properties have been formed. However, defects interfere with film patterning
and the fabrication of multi-layered structures. Several secondary phase precipitates have been identified, including CuO,
Y2O3, Cu-Ba-O, and Y2Cu2O5. Secondary phases resulting from a lack of stoichiometry can be eliminated by direct composition control in the MOD and three-target
sputtering techniques, and by composition control through the application of an externally applied magnetic field in single-target
off-axis sputtering. Secondary phases caused by contamination were also identified: Cr-Ba-O in off-axis sputtering, resulting
from contamination by the oxidized heater block; and BaSO4 in MOD, resulting from gas phase impurities. These results suggest that cation composition control is not sufficient to prevent
the formation of secondary phases and that small levels of contamination may prevent phasepure material from being formed. 相似文献
8.
Fernando H. garzon Ian D. Raistrick David R. Brown 《Journal of Electronic Materials》1992,21(5):483-485
The continuous monitoring of the conversion, of Y, Cu and BaF2 precursors to form superconductor thin films has been achieved using a fluorine-specific-ion electrode immersed in an effluent
gas-washing cell. High-quality thin films of YBa2Cu3O7-x
deposited on NdGaO3, LaA103 and LaGaO3, have been produced by limiting the wet oxygen annealing phase of the post-deposition anneal. When the films were over-annealed
in humidified oxygen the superconducting transition temperature as measured by inductive methods and the crystal quality,
determined by x-ray rocking curves were degraded. 相似文献
9.
Shih-Yuan Lin Ying-Chung Chen Chih-Ming Wang Kuo-Sheng Kao Chih-Yuan Chan 《Journal of Electronic Materials》2009,38(3):453-459
Calcium copper titanium oxide (CaCu3Ti4O12, abbreviated to CCTO) films were deposited on Pt/Ti/SiO2/Si substrates at room temperature (RT) by radiofrequency magnetron sputtering. As-deposited CCTO films were treated by rapid
thermal annealing (RTA) at various temperatures and in various atmospheres. X-ray diffraction patterns and scanning electron
microscope (SEM) images demonstrated that the crystalline structures and surface morphologies of CCTO thin films were sensitive
to the annealing temperature and ambient atmosphere. Polycrystalline CCTO films could be obtained when the annealing temperature
was 700°C in air, and the grain size increased signifi- cantly with annealing in O2. The 0.8-μm CCTO thin film that was deposited at RT for 2 h and then annealed at 700°C in O2 exhibited a high dielectric constant (ε′) of 410, a dielectric loss (tan δ) of 0.17 (at 10 kHz), and a leakage current density (J) of 1.28 × 10−5 A/cm2 (at 25 kV/cm). 相似文献
10.
Xinhua Zhu Jianmin Zhu Shunhua Zhou Zhiguo Liu Naiben Ming Shengguo Lu Helen Lai-Wah Chan Chung-Loong Choy 《Journal of Electronic Materials》2003,32(10):1125-1134
The (Ba1−xSrx)TiO3 (BST) ferroelectric thin films exhibit outstanding dielectric properties, even at high frequencies (>1 GHz), and large, electric-field
dielectric tunability. This feature makes them suitable for developing a new class of tunable microwave devices. The dielectric
properties and dielectric tuning property of BST thin films are closely related to the film compositions, substrate types,
and post-deposition process. The successful implementation of BST films as high-frequency dielectrics in electrically tunable
microwave devices requires a detailed understanding of both their processing and material properties. This paper will review
the recent progress of BST thin films as active dielectrics for tunable microwave devices. The technical aspects of BST thin
films, such as processing methods, post-annealing process, film compositions, film stress, oxygen defects, and interfacial
structures between film and substrate, are briefly reviewed and discussed with specific samples from the recent literature.
The major issues requiring additional investigations to improve the dielectric properties of BST thin films for tunable microwave
applications are also discussed. 相似文献
11.
Effects of excess Bi concentration, buffered Bi2O3 layer, and Ta doping on the orientation and ferroelectricity of chemical-solution-deposited (CSD) Bi3.25La0.75Ti3O12 (BLT) films on Pt/SiO2/Si(100) were studied. The optimum concentration of excess Bi added to the BLT films to achieve a larger remanent polarization
(2Pr) was 10 mol.%. The buffered Bi2O3 layers could reduce the temperature for c-axis-oriented growth of BLT films from 850°C to 700°C. However, two-step annealing,
i.e., first annealed at 650°C and then annealed at a temperature of 700–850°C, could effectively suppress the c-axis-oriented
growth and thus improve the 2Pr of BLT films. The improvement of the 2Pr of BLT films can be explained in terms of the large
polarization along the a-axis orientation and buffered Bi2O3 layers, which compensate the BLT films for Bi evaporation during annealing. The Ta doping can induce two contrary effects
on the 2Pr of BLT films. For the (Bi3.25La0.75)(Ti3−xTax)O12 (BLTTx) films with x=0.005, the effect of a decrease of oxygen vacancies would be dominant, resulting in the improvement
of 2Pr. Because the Ta concentration (x) in the BLTTx films exceeds 0.01, the effect of a decrease of grain size would become
dominant, resulting in the degradation of 2Pr. 相似文献
12.
D. Kumar R. D. Vispute O. Aboelfotoh S. Oktyabrsky K. Jagannadham J. Narayan P. R. Apte R. Pinto 《Journal of Electronic Materials》1996,25(11):1760-1766
Metallization of high-Tc superconductors using low resistivity metal oxides and Cu-Ge alloys has been investigated on high quality pulsed laser deposited
epitaxial YBa2Cu3O7-x (YBCO) films. Epitaxial LaNiO3 (LNO) thin films have been grown on YBCO films at 700°C using pulsed laser deposition. The specific resistivity of LNO was
measured to be 50 μΩ-cm at 300K which decreases to 19 μΩ-cm at 100K indicating good metallicity of the LNO films. The contact
resistance of LNO-YBCO thin film interface was found to be reasonably low (of the order of 10-4Ω-cm2 at 77K) which suggests that the interface formed between the two films is quite clean and LNO can emerge as a promising metal
electrode-material to YBCO films. A preliminary investigation related to the compatibility of Cu3Ge alloy as a contact metallization material to YBCO films is discussed. The usage of other oxide based low resistivity materials
such as SrRuO3 (SRO) and SrVO3 (SVO) for metallization of high-Tc YBCO superconductor films is also discussed. 相似文献
13.
Haematite (α-Fe2O3) thin films are prepared by two different chemical vapor deposition (CVD) processes: the atmospheric pressure CVD (APCVD)
and the plasma enhanced CVD (PECVD). The films are analyzed by x-ray diffraction and scanning electron microscopy; their gas-sensing
properties are also investigated. Experimental results show that APCVD α-Fe2O3 films are highly sensitive and selective to smoke while PECVD films are highly sensitive and selective to alcohol. A certain
amount of quadrivalent metal in the films has an effect on their sensitivity and selectivity to gases. It is found that the
films will “break down” under certain conditions. 相似文献
14.
Yoon-Bong Hahn Jong-Wha Kim Chang-Joo Youn In-Sun Lee 《Journal of Electronic Materials》1997,26(12):1394-1400
Dielectric PbTiO3-thin films were prepared on p-Si(100) substrate by plasma enhanced metalorganic chemical vapor deposition using high purity
Ti(O-i-C3H7)4, Pb(tmhd)2, and oxygen. As-deposited films were post-treated by rapid thermal annealing method, and the effect of annealing was examined
under various conditions. The deposition process was controlled by mixed-control scheme at temperatures lower than 350°C,
but controlled by heterogeneous surface reaction at temperatures greater than 350°C. The as-deposited films showed PbO structure
at 350∼400°C, but (100) and (101) PbTiO3 orientations started to appear at 450°C. The deposition rate was increased with rf power due to the enhanced dissociation
of Ti and Pb precursors. It was found that the concentration of oxygen plays an important role in crystallization of PbTiO3 during the rapid thermal annealing. A linear relationship was obtained between the dielectric constant of PbTiO3 films and the annealing temperature. However, the surface roughness and leakage current density increased mainly due to the
defects caused by volatilization of lead and the interface layer formed during the high temperature annealing. 相似文献
15.
Perovskite ferroelectric BaxSr1−xTiO3 (x = 0.5, 0.6, 0.7 and 0.8) thin films have been fabricated as metal-ferroelectric-insulator-semiconductor (MFIS) configurations using a sol-gel technique. The C-V characteristics for different Ba-Sr ratios and different film thicknesses have been measured in order to investigate the ferroelectric memory window effect. The results show that the memory window width increases with the increase both of Ba content and film thickness. This behavior is attributed to the grain size and dipole dynamics effect. It is found also that the memory window increases as the applied voltage increases. In addition, the leakage current density for the films is measured and it is found to be of the order of 10−8 A/cm2 for all tested samples, indicating that the films have good insulating characteristics. 相似文献
16.
Melt texture process of YBCO leads to a YBa2Cu3O7−x matrix where Y2BaCuO5 particles are observed. The Y2BaCuO5 inclusions size and distribution depend upon several parameters: YBa2Cu3O7-x grain size in the presintered, heating rate, dopants. The influence of an excess of Y2BaCuO5 and/or BaSnO3 on these Y2BaCuO5 particles are observed in the liquid phase and in the texture domain. According to the dopant used, two kinds of coarsening
of Y2BaCuO5 can be observed: an isotropic and an anisotropic. The control of the distribution of Y2BaCuO5 particle size is of primary interest to improve the efficiency of the MTG process. In particular large cooling rate (5°C/h)
during the texture formation could be used by adding Y2BaCuO5 + BaSnO3 to YBa2Cu3O7−x composition. 相似文献
17.
Jong-Gyu Kim Gwan-Ha Kim Kyoung-Tae Kim Chang-Il Kim 《Materials Science in Semiconductor Processing》2006,9(6):1108
The etching mechanism of (Bi4−xLax)Ti3O12 (BLT) thin films in Ar/Cl2 inductively coupled plasma (ICP) and plasma-induced damages at the etched surfaces were investigated as a function of gas-mixing ratios. The maximum etch rate of BLT thin films was 50.8 nm/min of 80% Ar/20% Cl2. From various experimental data, amorphous phases on the etched surface existed on both chemically and physically etched films, but the amorphous phase was thicker after the 80% Ar/20% Cl2 process. Moreover, crystalline “breaking” appeared during the etching in Cl2-containing plasma. Also the remnant polarization and fatigue resistances decreased more for the 80% Ar/20% Cl2 etch than for pure Ar plasma etch. 相似文献
18.
Zahid Hussain 《Journal of Electronic Materials》2002,31(6):615-630
Optical band gaps, Urbach inverse slopes, and coloration bands of various samples of annealed, microcrystalline LixMoO3-bronze thin films in the concentration range 0<x<0.6 were determined over the photon energy range from 0.4 eV to 4.2 eV.
On investigation, it is learned that the measured, optical band gaps do not shift rigidly over the annealing temperature range
293≤T≤423 K and, therefore, do not reveal the Burstein-Moss effect or reflect any stable, crystallographic phase transformation
during any investigated annealing cycle. A model relating the temperature-dependent optical gap to the real part of the refractive
index has also been developed, and this model fits very well to the annealed data within a maximum error of about 20%. Next,
using an oscillator model, a phonon energy of ∼0.08 eV was obtained, which is very close to the characteristic phonon energy
of the material, MoO3. Using this model, it becomes more certain that the contributions to the Urbach absorption edge for the annealed-molybdenum
bronzes are coming from the structural and compositional disorder. In another finding, it was found that the absorption-peak
energy for the annealed data was about 1.5–1.6 eV, which is still broad and asymmetrical, and therefore, it is almost of the
Mo6+ (or Mo4+)-Mo5+ intervalence or polaronic type. Using the polaron model, the half-bandwidth of the coloration bands of investigated, annealed
LixMoO3-thin films was found to be almost constant, which is consistent with the nonrigid band behavior. 相似文献
19.
V. R. Todt S. Sengupta Donglu Shi P. R. Sahm P. J. McGinn R. B. Poeppel J. R. Hull 《Journal of Electronic Materials》1994,23(11):1127-1130
YBa2Cu3Ox domains for levitation applications have been produced by a seeding technology that includes Nd1+x Ba2−x Cu3Oy seeds and melt-processing technologies such as conventional melt-textured growth, melt-texturing with PtO2 and Y2BaCuO5 additions, and the new solid-liquid-melt-growth technology. Large domains (∼20 mm) with high levitation forces (F1 up to 8.2 N) have been produced. The reproducibility of the results is good, and the capability of producing a large number
of pellets in a single batch indicates good potential for the production of large amounts of this material. 相似文献
20.
Wein-Duo Yang Yen-Hwei Chang Chia-Chia Huang Yu-Chung Chen 《Journal of Electronic Materials》2009,38(3):460-467
Highly sensitive CO gas sensors based on heterocontacts of ZnO:Al on La0.8Sr0.2Co0.5Ni0.5O3 (LSCNO) were fabricated successfully. La0.8Sr0.2Co0.5Ni0.5O3 thin films were coated on (100) silicon wafers by a sol-gel method including the Pechini process followed by a spin-coating
procedure. Then, ZnO:Al films prepared by radiofrequency (RF) magnetron sputtering at various oxygen partial pressures and
deposited on as-deposited La0.8Sr0.2Co0.5Ni0.5O3 films were investigated. The results revealed that the CO sensing ability of the film prepared with the ratio of O2/Ar = 5/5 (ratio of volume flow rate) was the worst, owing to the highest (002) plane orientation in the ZnO:Al film. In contrast,
the ZnO:Al film prepared with O2/Ar = 3/7 exhibited better CO sensitivity. Furthermore, all two-layer samples showed higher CO sensitivities than single-layer
samples. The CO sensitivity of ZnO:Al/La0.8Sr0.2Co0.5Ni0.5O3 thin film was 45% for 500 ppm CO at a sensing temperature of 200°C. 相似文献