共查询到20条相似文献,搜索用时 15 毫秒
1.
F. W. Van Keuls C. H. Mueller R. R. Romanofsky J. D. Warner F. A. Miranda H. Jiang 《Integrated ferroelectrics》2013,141(1-4):437-448
Abstract Historically, tunable dielectric devices using thin crystalline BaxSr1-x TiO3 (BST) films deposited on lattice-matched substrates, such as LaAlO3, have generally been grown using pulsed laser deposition (PLD). Highly oriented BST films can be grown by PLD but large projects are hampered by constraints of deposition area, deposition time and expense. The Metal-Organic Chemical Liquid Deposition (MOCLD) process allows for larger areas, faster turnover and lower cost. Several BST films deposited on LaAlO3 by MOCLD have been tested in 16 GHz coupled microstrip phase shifters. They can be compared with many PLD BST films tested in the same circuit design. The MOCLD phase shifter performance of 293° phase shift with 53 V/μm dc bias and a figure of merit of 47°/dB is comparable to the most highly oriented PLD BST films. The PLD BST films used here have measured XRD full-width-at-half-maxima (FWHM) as low as 0.047°. The best FWHM of these MOCLD BST films has been measured to be 0.058°. 相似文献
2.
J. Lindner F. Weiss J. P. Senateur W. Haessler G. Köbernik S. Oswald 《Integrated ferroelectrics》2013,141(1-4):53-59
Abstract BaTiO3 (BTO) and SrTiO3 (STO) and BaxSr1-xTiO3 (x=0–1) (BST) thin films have been epitaxially grown on LaAlO3 and SrTiO3:Nb at a substrate temperature of 800°C using a new liquid source delivery technique called injection MOCVD. A X-ray study evidenced FWHMs of 0.16° and 0.45° for SrTiO3 and BaTiO3 respectively. In a next step the feasibility of BaTiO3/SrTiO3 superlattices was studied. The multilayers obtained were epitaxially grown on LaAlO3 as well as on SrTiO3:Nb. The structural properties were studied using X-ray diffraction as well as XPS, proving the low interface roughness of 1nm. The XPS study also confirmed the absence of carbon contamination in the film. 相似文献
3.
Abstract Excellent single crystal BaxSr1-xTiO3 (BST) films were grown on LaAlO3 substrates using the metal-organic chemical liquid deposition (MOCLD) method. Very low losses (tanδ ∽0.002-0.008) were measured from these films at 400 KHz. Biaxially oriented BST films were successfully grown on polycrystalline YIG substrates using both MOCLD and pulsed laser deposition methods with biaxially oriented MgO and YSZ buffer layers. The dielectric losses of the films range from 0.005 to 0.015 while 25% of dielectric constant change was observed with 40V bias voltage up to 10 MHz. Both the dissipation and dielectric constant of the films remained nearly constants over a wide temperature range (77 K to 380 K). A dual-tuning microwave coplanar phase shifter using a BST film grown on a MgO buffered polycrystalline YIG substrate was fabricated. A significant phase shift was observed in GHz frequency range when an electric bias or a magnetic field was applied to the device. 相似文献
4.
JUN-KI CHUNG SANG SU KIM DONG SIK BAE MYUNG-HO KIM TAE KWON SONG SEUNG EON MOON 《组合铁电体》2013,141(1):415-421
ABSTRACT Stress controlled epitaxial ferroelectric Ba0.5Sr0.5TiO3 (BST) films have been deposited on Gd2O3/SrTiO3 by pulsed laser deposition with oxygen background pressure of 200 mTorr at the deposition temperature of 750°C. In order to control the stress in BST films, oxygen pressures for Gd2O3 buffer layers have been varied from 0.1 to 100 mTorr, while that of BST films have been fixed at 200 mTorr. It has been found that the lattice parameters of the BST films deposited on Gd2O3 were changed. Furthermore, microwave properties of co-planar waveguide (CPW) fabricated on BST films were investigated by a HP 8510C vector network analyzer from 1–20 GHz. Large dielectric tunabilities were observed from the CPW's fabricated on BST films deposited on Gd2O3 layers deposited at low and high oxygen pressures, 0.1 and 100 mTorr, respectively. 相似文献
5.
F. W. Van Keuls C. H. Mueller F. A. Miranda R. R. Romanofsky J. S. Horwitz W. Chang 《Integrated ferroelectrics》2013,141(1-4):49-61
Abstract We report measurements of gold circuits fabricated on four BaxSr1-xTiO3 ferroelectric films doped with 1% Mn grown on MgO substrates by laser ablation. Low frequency (1 MHz) measurements of σT and tanδ on interdigital capacitors are compared with high frequency measurements of phase shift and insertion loss on coupled microstrip phase shifters patterned onto the same films. The variation in temperature of both high and low frequency device parameters is compared. Annealed with amorphous buffer layer and unannealed films are compared. Room temperature figures of merit of phase shift per insertion loss of up to 58.4°/dB at 18 GHz and 400 V dc bias were measured. 相似文献
6.
Laura A. Wills Thorsten Schmitz Tina Reyes Jun Amano 《Integrated ferroelectrics》2013,141(1-4):429-440
Abstract Ba1-x SrxTiO3 (BST) thin films were deposited by reactive rf-magnetron sputtering onto Si substrates. The influence of the deposition parameters such as temperature and oxygen ambient on the dielectric constant of the films is presented. BST films deposited at 450°C and optimum conditions exhibited a dielectric constant of approximately 200 at frequencies as high as 1GHz. In addition, the films were found to have leakage current densities of <0.1μAmp/cm2 at fields of 5×105V/cm. An extrapolated lifetime greater than 10 years was obtained from stress tests at elevated temperatures and fields. These films compared favorably with published data. 相似文献
7.
《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
8.
Steven C. Stowell Yongfei Zhu Xubai Zhang Somnath Sengupta Louise C. Sengupta Alex J. Hsieh 《组合铁电体》2013,141(1-4):441-449
Abstract The RF sputtering method was utilized to deposit thin films of Ba1-xSrxTiO3 (BST). The targets utilized in these experiments were prepared from ceramic powders with different particle size. The goal of this work is to examine whether the particle size distribution of the target can affect the properties of the thin films fabricated by the sputtering method. The Atomic Force Microscope (AFM) was used to examine the grain size in the thin films. The composition of the thin films and the bulk materials were examined by Fourier Transform Infrared (FTIR) spectroscopy. The dielectric properties of the thin films were measured and compared to its bulk counterparts. It was found that on lattice matched electrodes of SrRuO3 on LaAlO3 substrates, the thin films deposited from ceramic targets manufactured from ball-milled powders had finer grain size than those deposited from targets made from unmilled powders. However, this phenomenon was not observed in the case of polycrystalline films deposited on platinized silicon wafers. 相似文献
9.
J. K. KIM S. S. KIM W. J. KIM J. K. CHUNG I. -S. KIM J. -S. SONG 《Integrated ferroelectrics》2013,141(1):423-428
ABSTRACT BaxSr1-xTiO3(BST) thin films with x = 0.5, 0.6, 0.7 and 0.8 were fabricated on p-type Si(100) substrates by a sol-gel spin coating method. All samples show the perovskite polycrystalline structures without the pyrochlore phase and have dense surface texture and crack-free uniform microstructures. The C-V characteristics of the BST thin film/p-type Si(100) capacitors exhibit clockwise hysteresis loops and also clearly show regions of accumulation, depletion and inversion corresponding to those of metal-ferroelectric-semiconductor structures. Furthermore, a constant memory window has been observed through the entire frequency ranges from 1 kHz to 10 MHz. 相似文献
10.
C. Couvert J.P. Contour O. Durand Y. Lemai^tre B. Marcilhac P. Woodall 《Journal of Electroceramics》2000,4(2-3):319-325
RHEED controlled ultra-thin buffer layers of SrTiO3 have been deposited on (1 0 0) MgO by pulsed laser deposition to grow YBa2Cu3O7 films for microwave applications. A buffer layer with a thickness from 5 to 40 unit cells of SrTiO3 is sufficient to expand to more than 60°C the range of deposition temperatures for which a low microwave surface resistance [Rs(10 GHz, 77 K)<0.5 m] is obtained. The Rs values are as low as those obtained on LaAlO3 substrates, furthermore they present a slightly lower magnetic field dependency. The XRD -scans show that the SrTiO3 seed layer induces an oriented epitaxial growth with the [1 0 0] axis of YBCO parallel to the one of MgO over this broadened range of deposition temperatures. This seed layer promoting effect is not observed with other oxides such as Ba0.15Sr0.85TiO3, CeO2, Ce1–x
La
x
O2. 相似文献
11.
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
12.
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
13.
Robert A. York Amit S. Nagra Padmini Periaswamy Orlando Auciello Stephen K. Streiffer Jaemo Im 《Integrated ferroelectrics》2013,141(1-4):177-188
Abstract Precise control of composition and microstructure is critical for the production of (BaxSr1?x)Ti1+yO3+z (BST) dielectric thin films with the large dependence of permittivity on electric field, low losses, and high electrical breakdown fields that are required for successful integration of BST into tunable high frequency devices. Here we review recent results on composition-microstructure-electrical property relationships of polycrystalline BST films produced by magnetron sputter deposition, that are appropriate for microwave devices such as phase shifters. Films with controlled compositions were grown from a stoichiometric Ba0.5Sr0.5TiO3 target by control of the background processing gas pressure. It was determined that the (Ba+Sr)/Ti ratios of these BST films could be adjusted from 0.73 to 0.98 by changing the total (Ar+O2) process pressure, while the O2/Ar ratio did not strongly affect the metal ion composition. Film crystalline structure and dielectric properties as a function of the (Ba+Sr)/Ti ratio are discussed. Optimized BST layers yielded capacitors with low dielectric losses (0.0047), among the best reported for sputtered BST, while still maintaining tunabili-ties suitable for device applications. These BST films were used to produce distributed-cir-cuit phase-shifters, using a discrete periodic loading of a coplanar waveguide with integrated BST varactors on high-resistivity silicon. Phase shifters yielding 30 degrees of phase shift per dB of insertion loss were demonstrated at 20GHz. 相似文献
14.
Abstract Ferroelectric Ba(1-x)SrxTiO3 (x = 0.5 and 0.25) thin films were grown on (001) LaAlO3 by using pulsed laser ablation. Extensive x-ray diffraction and selected area electron diffraction reveal that the as-grown films were (001) oriented with a good in plane relationship of <100>BSTO // <100>LAO. Rutherford Backscattering Spectroscopy ion-channeling studies suggested that the films had excellent epitaxial quality and crystallinity with an ion beam minimum yield χmin of only 2.6%. Atomically sharp interfaces were seen by cross-sectional high-resolution electron microscopy, indicated that the density of misfit dislocations was consistent with the lattice mismatch from the theoretical calculation. 相似文献
15.
《Integrated ferroelectrics》2013,141(1):863-869
Epitaxial (111) oriented ferroelectric (Ba1 ? xSrx)TiO3 (BST) films were deposited on MgO (111) single crystals using pulsed laser deposition. Structural properties of BST films were investigated using X-ray diffractometer. The dielectric properties of BST films were investigated under the dc bias field of 0–40 V using interdigital capacitors (IDT) fabricated by photolithography and etching process. The small signal dielectric properties of BST films were calculated by modified conformal mapping both the measured data using an impedance gain/phase analyzer and the reflection coefficient data measured using a HP 8510C vector network analyzer in 0.05–10 GHz at room temperature. The IDT capacitor based on (111) oriented BST film exhibits about 40% of capacitance change with an dc bias of 40 V which value is somewhat smaller than that of the IDT device based on (001) oriented BST film. But the dielectric quality factor value is about twice that of the device based on (001) oriented BST film. 相似文献
16.
Abstract Experimental and simulated spectra of microwave (30GHz) signal at the output of the coplanar waveguide (CPW) based on BaxSr1-xTiO3 film are presented and discussed. The modulation of BaxSr1-xTiO3 film dielectric constant by the application of high frequency (f ≈ 20MHz) control signal results in the generation of side frequency components in the output signal spectrum. The analysis of experimental data is performed on the basis of considering the CPW section with tunable effective dielectric constant as a phase modulator 相似文献
17.
Ba0.6Sr0.4Ti1+yO3 (BST, y?=?0.1, 0.15, 0.2, 0.25, 0.3) thin films were fabricated on Pt-coated silicon substrates by modified sol-gel techniques. It was found that the tunability of BST thin films and dissipation factor decreased with the increase of Ti content. The multilayer structure of Ba0.6Sr0.4Ti1+yO3(200 nm)/Ba0.6Sr0.4TiO3(100 nm)/Ba0.6Sr0.4Ti1+yO3 (200 nm; y?=?0.1, 0.2, 0.25) was designed to enhance the tunability. Our results indicated that the modified composition and multilayer structure were beneficial to lowering the dielectric dissipation and enhancing the tunability simultaneously. The tunability of 26.7% and dielectric dissipation of 0.013 were achieved for modified BST thin films. 相似文献
18.
《Integrated ferroelectrics》2013,141(1):877-885
(Ba0.5Sr0.5)TiO3 (BST) thin films were deposited by pulsed laser deposition (PLD) and investigated as a function of Ni dopant concentration in low and high frequency regions. In low frequency region (<10 MHz), the Ni-dopant concentration in BST films has a strong influence on the material properties including dielectric and tunable properties. Ni-doped (≤3 mol%) BST films showed denser, smoother morphologies and smaller grain sizes than those with 6 and 12 mol% Ni. Dielectric constant and loss of 3 mol% Ni-doped BST films were about 980 and 0.3%, respectively. In addition, tunability and figure of merit of 3 mol% doped BST films showed maximum values of approximately 39% and 108, respectively. In high frequency region (>1 GHz), the frequency tunability range at center frequency of undoped BST and 3 mol% Ni-doped BST coplanar waveguide (CPW) resonators showed 102 and 152 MHz, respectively at 30 V dc bias. The Ni-doped BST thin films are possible in applications of microwave tunable capacitors. 相似文献
19.
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
20.
R. Lyonnet A. Khodan A. Barthe´le´my J.-P. Contour O. Durand J.L. Maurice D. Michel J. Teresa de 《Journal of Electroceramics》2000,4(2-3):369-377
We have studied the pulsed laser deposition (PLD) of Zr1-xCexO2 and Ce1-xLaxO2-x/2 initially to grow buffer layers for perovskite films deposited on Si, LaAlO3, SrTiO3 and MgO and then to produce tunneling barriers for cuprate or manganite heterostructures. On (1 0 0) Si, the deposition of Zr1-xCexO2 (x = 0.12) produces a smooth epitaxial layer (R
RMS = 0.25/1m2), which allows the further deposition of high quality YBa2Cu3O7 (Tc 88 K) and La0.7Sr0.3MnO3 films. On the other hand, the use of Ce1-xLaxO2-x/2 (0 x 0.4) makes it possible to match the YBa2Cu3O7 and La0.7Sr0.3MnO3 layers to various substrates. The buffer layers are epitaxially grown with a 45° rotation of the in-plane axes with respect to those of the substrate, and the smoothness is high (R
RMS = 0.25/1m2). In the case of an ultra-thin barrier (2.5 nm) of Ce1-xLaxO2-x/2 sandwiched in a La0.7Sr0.3MnO3, the out-of-plane mismatch of 2 induces distortions at the interface steps, which propagate into the topmost La0.7Sr0.3MnO3 layer. This is in contrast to the case of SrTiO3 barriers where an ideal crystal continuity in the growth direction is observed. 相似文献