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851.
In this study, we monitored the HfAlO3 etch rate and selectivity to SiO2 as a function of the etch parameters (gas mixing ratio, RF power, DC-bias voltage, and process pressure). A maximum etch rate of 52.6 nm/min was achieved in the 30% BCl3/(BCl3 + Ar) plasma. The etch selectivity of HfAlO3 to SiO2 reached 1.4. As the RF power and the DC-bias voltage increased, the etch rate of the HfAlO3 thin film increased. As the process pressure decreased, the etch rate of the HfAlO3 thin films increased. The chemical state of the etched surfaces was investigated by X-ray Photoelectron Spectroscopy (XPS). According to the results, the etching of HfAlO3 thin films follows the ion-assisted chemical etching mechanism. 相似文献
852.
Phase evolution during the synthesis of Cu(InGa)Se2 from glass/Mo/(In1 − xGax)2Se3/CuSe bilayer precursors were investigated by in-situ high-temperature X-ray diffraction. With Se overpressure, CuSe was transformed to CuSe2 at 220 °C. The CuSe2 phase returned to CuSe by releasing Se at its peritectic point of 330 °C, where the formation of Cu(InGa)Se2 phase was initiated as well. Rapid thermal processing of bilayer precursors showed the potential of fast formation of Cu(InGa)Se2 within 2–5 min reaction with fairly uniform Ga and In depth profile. Further annealing with Se overpressure caused the formation of MoSe2 at the interface of Mo and Cu(InGa)Se2. 相似文献
853.
The novel Fe/Nb co-doped SrCo1 ? 2x(Fe,Nb)xO3 ? δ (x = 0.05, 0.10) perovskite oxides were synthesized by the solid-state method. Structural and chemical stability of the SrCo1 ? 2x(Fe,Nb)xO3 ? δ (x = 0.05, 0.10) oxides were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and X-ray diffraction (XRD). The results demonstrated that the structural and chemical stability of the Fe/Nb co-doped SrCo1 ? 2x(Fe,Nb)xO3 ? δ (x = 0.05, 0.10) is improved significantly. The oxygen sorption properties of the SrCo1 ? 2x(Fe,Nb)xO3 ? δ (x = 0.05, 0.10) oxides were investigated between 300–900 °C in air, and the high oxygen sorption capacity of 11.5 and 10.3 mL O2 (STP)/g oxide, respectively, are obtained. 相似文献
854.
We present a new method to improve the oxygen flux properties and stability of Ba0.5Sr0.5Co0.8Fe0.2O3 − δ tube membrane using a thin layer of La0.6Sr0.4Ti0.3Fe0.7O3 − δ as protective coatings. The first relevant result is that the La0.6Sr0.4Ti0.3Fe0.7O3 − δ protective layer had an extraordinary positive effect on improving the oxygen permeation flux of the tubular Ba0.5Sr0.5Co0.8Fe0.2O3 − δ membranes. La0.6Sr0.4Ti0.3Fe0.7O3 − δ-coated Ba0.5Sr0.5Co0.8Fe0.2O3 − δ tubular membrane showed the highest oxygen permeability with the flux reaching ~ 3 ml cm−2 min−1 (oxygen purity > 99%) at 950 °C in static atmospheric pressure through a 1.0 mm thick membrane. 相似文献
855.
In this study, Sn-free Zr–1.5Nb–O–P alloys were manufactured and their mechanical properties were characterized. The ultimate tensile strength (UTS) of cold rolled Zr–1.5Nb–O–P alloy with 160 ppm phosphorous (680 MPa) were close to that of a commercially available Zr–1Nb–1Sn–0.1Fe alloy (720 MPa), achieving a good mechanical strength without the addition of Sn, an effective solution strengthening element. The UTS of recrystallized Zr–1.5Nb–O–P alloy with 160 ppm phosphorous (533 MPa) was far greater than that of a commercially available Zr–1Nb–O (323 MPa) because of the strengthening due to higher Nb and oxygen content combined with phosphorous strengthening. The activation volumes for the cold rolled Zr–1.5Nb–P alloys were not much different from those of annealed Zr–1.5Nb–P alloys despite the higher dislocation density in the cold rolled alloys. Insensitivity of the activation volume to the dislocation density and the decrease of the activation volume with the addition of phosphorous support the suggestion linking the activation volume with the activated bulge of dislocations limited by segregation of oxygen and phosphorous atoms. 相似文献
856.
857.
Matte GM Van Neer PL Danilouchkine MG Huijssen J Verweij MD de Jong N 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2011,58(3):533-546
Second-harmonic imaging is currently one of the standards in commercial echographic systems for diagnosis, because of its high spatial resolution and low sensitivity to clutter and near-field artifacts. The use of nonlinear phenomena mirrors is a great set of solutions to improve echographic image resolution. To further enhance the resolution and image quality, the combination of the 3rd to 5th harmonics--dubbed the superharmonics--could be used. However, this requires a bandwidth exceeding that of conventional transducers. A promising solution features a phased-array design with interleaved low- and high-frequency elements for transmission and reception, respectively. Because the amplitude of the backscattered higher harmonics at the transducer surface is relatively low, it is highly desirable to increase the sensitivity in reception. Therefore, we investigated the optimization of the number of elements in the receiving aperture as well as their arrangement (topology). A variety of configurations was considered, including one transmit element for each receive element (1/2) up to one transmit for 7 receive elements (1/8). The topologies are assessed based on the ratio of the harmonic peak pressures in the main and grating lobes. Further, the higher harmonic level is maximized by optimization of the center frequency of the transmitted pulse. The achievable SNR for a specific application is a compromise between the frequency-dependent attenuation and nonlinearity at a required penetration depth. To calculate the SNR of the complete imaging chain, we use an approach analogous to the sonar equation used in underwater acoustics. The generated harmonic pressure fields caused by nonlinear wave propagation were modeled with the iterative nonlinear contrast source (INCS) method, the KZK, or the Burger's equation. The optimal topology for superharmonic imaging was an interleaved design with 1 transmit element per 6 receive elements. It improves the SNR by ~5 dB compared with the interleaved (1/2) design reported in literature. The optimal transmit frequency for superharmonic echocardiography was found to be 1.0 to 1.2 MHz. For superharmonic abdominal imaging this frequency was found to be 1.7 to 1.9 MHz. For 2nd-harmonic echocardiography, the optimal transmit frequency of 1.8 MHz reported in the literature was corroborated with our simulation results. 相似文献
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