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1.
Large area Ba1 − xSrxTiO3 (BST) thin films with x = 0.4 or x = 0.5 were deposited on 75 mm diameter Si wafers in a pulsed laser deposition (PLD) chamber enabling full-wafer device fabrication using standard lithography. The deposition conditions were re-optimized for large PLD chambers to obtain uniform film thickness, grain size, crystal structure, orientation, and dielectric properties of BST films. X-ray diffraction and microstructural analyses on the BST films grown on Pt/Au/Ti electrodes deposited on SiO2/Si wafers revealed films with (110) preferred orientation with a grain size < 100 nm. An area map of the thickness and crystal orientation of a BST film deposited on SiO2/Si wafer also showed (110) preferred orientation with a film thickness variation < 6%. Large area BST films were found to have a high dielectric tunability of 76% at an electric field of 400 kV/cm and dielectric loss tangent below 0.03 at microwave frequencies up to 20 GHz and a commutation quality factor of ~ 4200.  相似文献   

2.
BST thin films have been investigated as potential candidates for use in frequency agile microwave circuit devices. Stoichiometric (Ba1 − xSrx)TiO3 (BST) thin films have been prepared on Pt/SiO2/Si substrates using sol-gel method. The BST films were characterized by X-ray fluorescence (XRF) spectroscopy analysis, X-ray diffraction (XRD), scanning electron microscope (SEM) and electrical measurements. The relationships of processing parameters, microstructures, and dielectric properties are discussed. The results show that the films exhibit pure perovskite phase through rapid thermal anneal at 700 °C and their grain sizes are about 20-40 nm. The dielectric constants of BST5, BST10, BST15 and BST20 are 323, 355, 382 and 405, respectively, at 80 kHz.  相似文献   

3.
KTa1 − xNbxO3 (KTN) thin films were grown by pulsed laser deposition on sapphire and MgO substrates. Their structural and high frequency dielectric characteristics evidenced the strong influence of the substrate and suggested possible KTN/MgO interdiffusion that could be responsible for the lower dielectric losses obtained on this substrate. Both undoped and 6% MgO-doped KTN thin films were then grown on sapphire. Dielectric measurements performed at 12.5 GHz by a resonant cavity perturbation method evidenced reduction of losses by MgO-doping. Loss tangent (tan δ) was reduced by a factor of 3 in comparison with undoped films grown on sapphire.  相似文献   

4.
High dielectric constant and low loss ceramics in the system Ba2 − xSrxLa3Ti3NbO15 (x = 0-1) have been prepared by conventional solid-state ceramic route. Ba2 − xSrxLa3Ti3NbO15 solid solutions adopted A5B4O15 cation-deficient hexagonal perovskite structure for all compositions. The materials were characterized at microwave frequencies. They show a linear variation of dielectric properties with the value of x. Their dielectric constant varies from 48.34 to 43.03, quality factor Qu × f from 20,291 to 39,088 GHz and temperature variation of resonant frequency from 8 to 1.39 ppm/°C as the value of x increases. These low loss ceramics might be used for dielectric resonator (DR) applications.  相似文献   

5.
The Al doping effects on high-frequency magneto-electric properties of Zn1 − x − yAlxCoyO (x = 0-10.65 at.%) thin films were systematically studied. In the current work, the Zn1 − x − yAlxCoyO thin films were deposited by magnetron co-sputtering onto quartz substrates. The magneto-impedance spectra of the thin films were measured by an impedance analyzer. Among all the doped films studied, the thin film with 6.03 at.% Al-doping showed the highest ac conductivity and relaxation frequency. To characterize the relaxation mechanism underlying the magneto-electric properties, a Cole-Cole impedance model was applied to analyze the impedance spectra. The analyzed result showed that the magneto-impedance of the Zn1 − x − yAlxCoyO is contributed by multiple processes of magnetization dynamics and dielectric relaxation. The results imply that Zn1 − x − yAlxCoyO may be applicable for high-frequency magneto-electric devices.  相似文献   

6.
Sintering behavior, microstructure and microwave dielectric properties of Li2+xTiO3 (0 ≤ x ≤ 0.2) ceramics have been studied by X-ray diffraction (XRD), scan electron microscopy (SEM), Raman spectra, dilatometery and microwave resonant measurement in this research. Homogeneous non-stoichiometric composition with rock salt structure existed for Li2+xTiO3 (0 ≤ x ≤ 0.2) ceramics. The sintering temperature was successfully reduced and highly densified sample could be obtained with appropriate excessive amount of lithium (x = 0.08). A transient reactive liquid phase sintering mechanism was proposed. The preferred orientation of grain growth and micro-cracks existed in the Li2TiO3 (x = 0) sample disappeared in the lithium excessive samples with x ≥ 0.08. The microwave dielectric properties varied significantly with the excessive amount of lithium. Optimized microwave dielectric properties were obtained for the x = 0.08 composition: ?r = 24.6, Q × f = 66,000 GHz, and τf = 22.1 ppm/°C.  相似文献   

7.
Nanostructured (Pb1 − xSrx)TiO3 (PST) (x = 0.1, 0.2 and 0.3) thin films have been prepared by chemical solution deposition process using spin coating technique. The solution as such was deposited on Pt/Ti/SiO2/Si substrates and annealed at 650 °C/3h. Nanograins dependent dielectric properties of PST films show dielectric constant up to the higher frequency region, low losses, large tunability and phase transition at small temperature. The impedance data has been fitted by Cole-Cole model to study the effect of grain boundaries on the dielectric properties. The current-voltage characteristics have been measured to study leakage current in PST films and described by Poole-Frenkel emission model. It is suggested that the key carrier transport process in PST films is emission of electrons from a trap state near the metal-film interface into a continuum of states associated with each conductive dislocation. The activation energy value for carrier transport in PST films is obtained from temperature-dependent current-voltage characteristics.  相似文献   

8.
This paper reports the structural and dielectric properties of Ba(Ti1 − xZrx)O3 (x = 0-0.3) ceramics. Single-phase solid solutions of the samples were determined by X-ray diffraction. Microscopic observation by scanning electron microscope revealed dense, single-phase microstructure with large grains (20-60 μm). The evolution of dielectric behavior from a sharp ferroelectric peak (for x ≤ 0.08) to a round dielectric peak (for 0.15 ≤ x ≤ 0.25) with pinched phase transitions and successively to a ferroelectric relaxor (for x = 0.3) was observed with increasing Zr concentration. Compared with pure BaTiO3, broaden dielectric peaks with high dielectric constant of 25,000-40,000 and reasonably low loss (tanδ: 0.01-0.06) in the Ba(Ti1 − xZrx)O3 ceramics have been observed, indicating great application potential as a dielectric material.  相似文献   

9.
Pb(ZrxTi1 − x)O3 (x = 0.35, 0.40, 0.60, 0.65) thin films were prepared by sol-gel spin on technique. From the X-ray diffraction analysis, PZT films with Zr-rich compositions (x = 0.60 and 0.65) had (111) preferential orientation and the preferential orientation changed to (100) for Ti-rich compositions (x = 0.35 and 0.40). The dielectric measurements on the above compositions at room temperature showed that the dielectric constant values were higher in Zr-rich compositions compared to Ti-rich compositions. The ferroelectric behavior measured in terms of the remnant polarization (Pr) and coercive field (Ec) up to an applied field of 260 kV/cm depicted that the Zr-rich PZT films with (111) preferential orientation had higher Pr and lower Ec values compared to the Ti-rich PZT films with (100) preferential orientation can be understood from the domain switching mechanism.  相似文献   

10.
Transparent conducting thin films of Al-doped and Ga-doped Zn1 − xMgxO with arbitrary Mg content x were deposited on glass substrates by simultaneous RF-magnetron sputtering of doped ZnO and MgO targets, and their fundamental properties were characterized. MgO phase separation in Zn1 − xMgxO films was not detected by X-ray diffraction. The Zn1 − xMgxO films show high optical transparency in the visible region. Although the carrier density of the Zn1  xMgxO films decreased with increasing x, the Zn1 − xMgxO films showed good electrical conductivity; electrical resistivity as low as 8 × 10− 4 Ω ·cm was achieved for the Zn0.9Mg0.1O:Ga thin film.  相似文献   

11.
Low-temperature (~ 250 °C) layer exchange crystallization of poly-Si1 − xGex (x = 1-0) films on insulators has been investigated for realization of advanced flexible devices. We propose utilization of Au as catalyst to enhance the crystallization at low temperatures. By annealing (~ 250 °C, 20 h) of the a-Si1 − xGex (x = 1-0)/Au stacked structures formed on insulating substrates, the SiGe and Au layers exchange their positions, and Au/poly-SiGe stacked structures are obtained. The Ge fractions of the obtained poly-SiGe layers are identical to that of the initial a-SiGe layers, and there is no Si or Ge segregation. This low temperature crystallization technique enables poly-SiGe films on plastic substrates, which are essential to realize advanced flexible devices.  相似文献   

12.
Zn1 − xMgxO thin films of various Mg compositions were deposited on quartz substrates using inexpensive ultrasonic spray pyrolysis technique. The influence of varying Mg composition and substrate temperature on structural, electrical and optical properties of Zn1 − xMgxO films were systematically investigated. The structural transition from hexagonal to cubic phase has been observed for Mg content greater than 70 mol%. AFM images of the Zn1 − xMgxO films (x = 0.3) deposited at optimized substrate temperature clearly reveals the formation of nanorods of hexagonal Zn1 − xMgxO. The variation of the cation-anion bond length to Mg content shows that the lattice constant of the hexagonal Zn1 − xMgxO decreases with corresponding increase in Mg content, which result in structure gradually deviating from wurtzite structure. The tuning of the band gap was obtained from 3.58 to 6.16 eV with corresponding increase in Mg content. The photoluminescence results also revealed the shift in ultraviolet peak position towards the higher energy side.  相似文献   

13.
The (0 0 l) textured BaBi2(Nb1 − xVx)2O9 (where x = 0, 0.03, 0.07, 0.1 and 0.13) ceramics were fabricated via the conventional melt-quenching technique followed by high temperature heat-treatment (800-1000 °C range). The influence of vanadium content and sintering temperature on the texture development and relative density were investigated. The samples corresponding to the composition x = 0.1 sintered at 1000 °C for 10 h exhibited the maximum orientation of about 67%. The Scanning electron microscopic studies revealed the presence of platy grains having the a-b planes perpendicular the pressing axis. The dielectric constant and the pyroelectric co-efficient values in the direction perpendicular to the pressing axis were higher. The anisotropy in the dielectric constant is about 100 (at 100 kHz) at the dielectric maximum temperature and anisotropy in the pyroelectric co-efficient is about 50 μC cm−2 °C−1 in the vicinity of pyroelectric anomaly for the sample corresponding to the composition x = 0.1 sintered at 1000 °C. Higher values of the dielectric loss and electrical conductivity were observed in the direction perpendicular to the pressing axis which is attributed to the high oxygen ion conduction in the a-b planes.  相似文献   

14.
Xiaofei Han  Zhude Xu 《Thin solid films》2009,517(19):5653-989
Cd1 − xZnxO nanocrystalline thin films with rock-salt structure were obtained through thermal decomposition of Cd1 − xZnxO2 (x = 0, 0.37, 0.57, 1) thin films which were electrodeposited from aqueous solution at room temperature. X-ray diffraction results showed that the Zn ions were incorporated into rock salt-structure of CdO and the crystal lattice parameters decreased with the increase of Zn contents. The bandgaps of the Cd1 − xZnxO thin films were obtained from optical transmission and were 2.40, 2.51, 2.63 and 3.25 eV, respectively.  相似文献   

15.
Ba(1 − x)SrxTiO3 powders with different Ba/Sr ratios (x = 0.10, 0.25, 0.40, 0.55, 0.70) and La-doped Ba0.9Sr0.1TiO3·yLa powders (y = 0.002, 0.004, 0.006, 0.008, 0.010) have been prepared by sol-gel technology using dehydrated barium-acetate, strontium-carbonate, lanthanum-nitrate, and titanium-isopropoxide as raw materials. The experimental results show that the dielectric properties of Ba(1 − x)SrxTiO3 powders depend on the Ba/Sr ratios. When the Sr fraction is 0.10, the dielectric constant is relatively higher and the dielectric loss is relatively lower, which are more than 2000 and less than 2.0 × 10− 2 at 1000 Hz, respectively, the most important is that this kind of powder has better frequency stability. La-doping can increase the dielectric constant distinctly, but the dielectric loss can also be increased. Their dielectric properties at 1.0 × 103 Hz are better than those at 1.0 × 105 Hz. At 1.0 × 103 Hz the dielectric constant is much higher, while the dielectric loss is much lower. The dielectric constant of different La-doping contents is nearly 3.5 × 104 and the dielectric loss is less than 0.20 when La fraction is 0.008. The La-doped BST sample also has better frequency stability, especially at high frequency. La-doped BST thin films are successfully deposited on mild steel substrates by using plasma spray system with suspension precursors of Ba0.90Sr0.10TiO3·0.8La powders. The XRD patterns of Ba0.90Sr0.10TiO3 and Ba0.90Sr0.10TiO3·0.8La powders are almost the same. No new peaks appear after La-doping, but the peaks move slightly to a larger degree, which indicates that the element La has entered the lattice of the Ba0.90Sr0.10TiO3 and has made the constant of the crystal cell reduce. The XRD pattern of the thin films is just like that of the Ba0.90Sr0.10TiO3·0.8La powders except a peak corresponding to Fe substrate. The SEM results show that the thin films have a uniform and smooth surface. The morphology of cross-section shows a columnar grain structure indicating smooth surface and uniform thickness of the film. The thickness of the film is about 15 um. The thin films obtained are expected to be prospective material for applications in tunable microwave devices.  相似文献   

16.
A comparative study of the microstructure and dielectric properties between Ba1−xCaxTiO3 (BCT) ceramics and films were performed in the whole Ca concentration range of x = 0-1. The ceramics were prepared by conventional solid-state reaction technique and the films by the method of pulsed-laser deposition. X-ray diffraction (XRD) study of the BCT ceramics exhibited a pure tetragonal phase for x = 0-0.25, a tetragonal-orthorhombic diphase for x = 0.25-0.85 and a pure orthorhombic phase for x = 0.90-1.00. And the dielectric phase transition temperature from tetragonal to cubic was marginally affected by the Ca doping into BaTiO3. However, BCT films deposited on Pt/Si/SiO2/Si substrates showed a different microstructure and dielectric properties. Tetragonal-orthorhombic diphase was not found in the BCT films for x = 0.25-0.85, and a large decrease of the Curie point and diffuse phase transition were observed in the BCT films. Based on the compositional analysis, such phenomena were ascribed to the occupancy of some Ca2+ to the Ti4+ sites in the BCT films.  相似文献   

17.
Amorphous thin films of glassy alloys of Se75S25 − xCdx (x = 2, 4 and 6) were prepared by thermal evaporation onto chemically cleaned glass substrates. Optical absorption and reflection measurements were carried out on as-deposited and laser-irradiated thin films in the wavelength region of 500-1000 nm. Analysis of the optical absorption data shows that the rule of no-direct transitions predominates. The laser-irradiated Se75S25 − xCdx films showed an increase in the optical band gap and absorption coefficient with increasing the time of laser-irradiation. The results are interpreted in terms of the change in concentration of localized states due to the shift in Fermi level. The value of refractive index increases decreases with increasing photon energy and also by increasing the time of laser-irradiation. With the large absorption coefficient and change in the optical band gap and refractive index by the influence of laser-irradiation, these materials may be suitable for optical disc application.  相似文献   

18.
Electrical and magnetoelectric properties of magnetoelectric (ME) composites containing barium titanate as electrical component and a mixed Ni-Co-Mn ferrite as the magnetic component are reported. The ME composites with a general formula (x)BaTiO3 + (1 − x)Ni0.94Co0.01Mn0.05Fe2O4 where x varies as 0, 0.55, 0.70, 0.85 and 1 were prepared by standard double sintering ceramic method. The presence of both the phases was confirmed by X-ray diffraction technique. The dc resistivity was measured as a function of temperature. The variation of dielectric constant (?) and loss tangent (tan δ) with frequency (100 Hz-1 MHz) and with temperature was studied. The conduction is explained on the basis of small polaron model based on ac conductivity measurements. The static value of ME conversion factor i.e. dc (ME)H was studied as function of intensity of magnetic field. The changes were observed in dielectric properties as well as ME effect as the molar ratio of the components was varied. A maximum value of ME conversion factor of 610 μV/cm Oe was observed in the case of a composite containing 15 mol% ferrite phase.  相似文献   

19.
The dielectric function of bulk CuAl1 − xInxSe2 with composition x varying from x = 0.07 to x = 0.6 were studied over the photon energy region 1.0-6.0 eV at room temperature by spectroscopic ellipsometry. Information on the inter-band optical transitions was obtained from the results of the standard critical point analysis of the obtained dielectric function. With increasing Indium content, all spectral features of the obtained dielectric functions were found to gradually shift towards lower energies. The details of this shift for each critical point retrieved from the obtained dielectric function were disclosed. A compositional dependence of the optical transitions in Γ point of the Brillouin zone was verified to be strong. Such dependence for N and T points turned out to be weak by comparison. The later fact was accounted for a small compositional shift of the conduction band states in N and T points as compared to Γ point.  相似文献   

20.
Thin films of Bi3.15Nd0.85Ti3O12 (BNT) and Bi3.15Nd0.85Ti3 − xZrxO12 (BNTZx, x = 0.1 and 0.2) were fabricated on Pt/TiO2/SiO2/Si(100) substrates by a chemical solution deposition (CSD) technique at 700 °C. Structures, surface morphologies, leakage current characteristics and Curie temperature of the films were studied as a function of Zr ion content by X-ray diffraction, atomic force microscopy, ferroelectric test system and thermal analysis, respectively. Experimental results indicate that Zr ion substitution in the BNT film markedly decreases the leakage current of the film, while almost not changing the Curie temperature of the film, which is at about 420-460 °C. The decrease of the leakage current in BNTZx films is that the conduction by the electron hopping between Ti4+ and Ti3+ ions is depressed because Zr4+ ions can block the path between two adjacent Ti ions and enlarge hopping distance.  相似文献   

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