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1.
High-TC superconducting Y-Ba-Cu-O films were prepared on certain ceramic and metal substrates by pyrolysis of 2-ethylhexanoates. Only the films on MgO, yttria-stabilized zirconia (YSZ), and Ag substrates exhibited the superconducting transition above liquid nitrogen temperature. Transition temperatures (TC) of 82, 85, and 82 K were observed in films of MgO, YSZ, and Ag substrates. The important factors in preparing superconducting films on substrates are the reactivity of the films and the substrates and the difference in their thermal expansions. The Y-Ba-Cu-O films were well suited for use with MgO, YSZ, and Ag substrates. Long superconducting tapes were produced on Ag substrate; flexible tape with a critical current density JC of 3 · 103 A/cm2 at 77 K has now been prepared.  相似文献   

2.

We report the preparation and characterization of YBa2Cu3O7 (YBCO) films grown onto SrTiO3 and YSZ substrates by the trifluoroacetates chemical solution deposition method and following sintering with oxygen atmosphere at 860 °C. The X-ray diffraction (XRD) reveals (00?) – oriented crystallites indicating epitaxial growth of the films in the c-direction. Despite granular morphology and the presence of Y2BaCuO5 and CuO as minor secondary phases, the technique shows the successful formation of the superconducting YBCO and preventing the formation of the unwanted BaCO3 phase. Rocking curve measurements of the (005) reflection for the YBCO/SrTiO3 was fitted with one Gaussian function with full width at the half maximum (FWHM) of 0.44° confirming that it consists of YBCO crystallites with different texture. For the sample grown on YSZ, the rocking curve was fitted with two Gaussian functions, one corresponding to the YBCO layer (FWHM?=?0.4°) and another to the substrate (FWHM?=?0.3°). The magnetic measurements taken in zero field cooling and field cooling modes confirm the formation of the superconducting YBCO with critical temperatures (TC) 91.8 and 85.7 K for the samples grown onto YSZ and SrTiO3, respectively. The critical current density (JC) curves indirectly calculated by using the Bean´s model from the M(T) loops were JC?~?109 A/cm2 for the sample deposited onto YSZ and JC?~?107A/cm2 for the YBCO deposited onto SrTiO3. Overall, the difference in TC and JC values between both samples could be related to their difference in oxygen content, porosity, hole concentration per Cu ion and the presence of secondary phases.

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3.
ABSTRACT

The integrated single element infrared detectors were developed for high-loading smart munition application using (Ba0.65Sr0.35)TiO3 (BST) pyroelectric films and SiO2 thermal insulating layer. (Ba,Sr)RuO3 (BSR) seeding-layer was deposited on the Pt/Ti/SiO2/Si to induce BST films c-axis preferred orientation growth. The capacitance dependant with temperature of BST films were measured at the temperature ranging from 230 K to 340 K, releasing that the temperature coefficient of capacitance was 1.6%/K. The pyroelectric coefficient of BST films was 7.45 × 10? 7 C/K cm2 measured by dynamic method. Infrared response evaluation of the fabricated sensor has been carried out with D* of 6.34 × 107 cm Hz1/2/W indicating that the integrated infrared detectors have potential application as gun-launched smart munition seeker.  相似文献   

4.
Pb(Zr0.52Ti0.48)O3 films with highly uniform c-axis orientation were fabricated on PbTiO3 (PT)/ Pt(111)/SiO2/Si(100) substrates by hot isostatic pressing (HIP) from the amorphous state. All the PZT samples HIP-treated 500°C for 1 h under gas pressures of 1.0–2.0 MPa showed the preferred (001) orientation with c-axis orientation, α > 0.80. The relative permittivity tended to decrease gently with increasing HIP pressure, whereas the dielectric loss increased almost linearly in the 1.5–100 MPa. The PZT sample treated at 1.5 MPa had a symmetric and slim hysteresis loop shape with a remanent polarization, P r = 15 μ C/cm2 and coercive field, E c = 60 kV/cm. Both samples treated at 10 and 100 MPa exhibited almost the fatigue-free behavior that resisted degradation even after 3 × 1010 cycles.  相似文献   

5.
《Integrated ferroelectrics》2013,141(1):769-779
Ferroelectric Na0.5K0.5NbO3 (NKN) thin films were grown on the Pt80Ir20 polycrystalline substrates by pulsed laser deposition (PLD) and radio frequency-magnetron sputtering (RF) technique using the same stoichiometric Na0.5K0.5NbO3 ceramic target. X-ray diffraction proved both PLD- and RF-made Na0.5K0.5NbO3/Pt80Ir20 films are single phase and have preferential c-axis orientation. Temperature dependence of dielectric permittivity reveals the presence of two phase transitions around 210 and 410°C. Capacitance vs. applied voltage C-V @ 100 kHz, I-V, and P-E hysteresis characteristics recorded for the vertical capacitive structures yielded loss tanδ = 0.026 and 0.016, tunability about 44.5 and 30% @ 100 kV/cm, Ohmic resistivity 6.7 × 1012 Ω·cm and 0.2 × 1012 Ω·cm, remnant polarization 11.7 and 9.7 μC/cm2, coercive field 28.0 and 94.6 kV/cm for PLD- and RF-films, respectively. Piezoelectric test carried out in hydrostatic conditions showed piezoelectric coefficient d H = 21 for PLD-NKN and 15 pC/N for RF-NKN film.  相似文献   

6.
Abstract

The effects of deposition temperature on the properties of thin films of sputtered lead-zirconate-titanate (PZT) have been studied for ULSI DRAM storage capacitor dielectric applications. The films were deposited by reactive dc magnetron sputtering from a multi-component target. The grain size for the films deposited at 400°C was found to be less than 1000 Å, while it was ~ 10–30 μm for films deposited at 200°C. Small grain-sized material is desirable since it leads to better cell-to-cell uniformity in terms of charge storage capacity and other electrical and reliability properties. The optimum lead compensation was found to increase as the deposition temperature (T dep) increased. Leakage current density stays fairly constant as T dep is varied. As-deposited films, with a deposition temperature of 500°C, were rich in the perovskite phase and showed a high charge storage density of 11.2 μC/cm2 and a low leakage current density of 5.1 × 10?7 A/cm2 (both at 1.5 V). This implies the possibility of eliminating the high temperature crystallization-annealing step.  相似文献   

7.
Abstract

PZT thin films with a uniform distribution of components were prepared by plasma enhanced chemical vapor deposition (PECVD) using Pb(C2H5)4, Z (O-i-C4H9)4, Ti(O-i-C3H7)4, and oxygen. The crystallization of films was occure after annealing in the temperature range between 450 and 550°C under O2 ambient for 1 hr. The significant change of Pb concentration in PECVD PZT thin films was not observed in the relation to annealing temperature and time. The dielectric constant PECVD PZT thin films increased with the Ti content, showed the maximum value in the vicinity of morphotropic phase boundary (MPB) composition of PZT material, and decreased with the Ti content. The leakage current density of PZT (65/35) thin film of 180 nm in thickness was 3·37 × 10?7 A/cm2 at the applied voltage of 3 V. Remanent polarization increased with increasing of Zr content in the film and coercive field was nearly independent of the composition. The typical values of electrical properties were εr = 570, Ec = 90 kV/cm, and Pr = 19 μC/cm2 in the PECVD PZT (54/46) thin film of 220 nm in thickness.  相似文献   

8.
c-axis oriented Bi3.25La0.75Ti3O12 (BLT) thin films were grown on a RuO2 top electrode deposited on a (100) SiO2/Si substrate by the polymeric precursor method. X-ray diffraction and atomic force microscope investigations indicate that the films exhibit a dense, well crystallized microstructure having random orientations with a rather smooth surface morphology. The electrical properties of preferred oriented Bi3.25La0.75Ti3O12 (BLT) thin films deposited on RuO2 bottom electrode leaded to a large remnant polarization (P r ) of 17.2 μC/cm2 and (V c ) of 1.8 V, fatigue free characteristics up to 1010 switching cycles and a current density of 2.2 μA/cm2 at 5 V. We found that the polarization loss is insignificant with nine write/read voltages at a waiting time of 10,000 s. Independently of the applied electric field the retained switchable polarization approached a nearly steady-state value after a retention time of 10 s.  相似文献   

9.
Transition metal (Ni, Mn, Cu) doped Bi0.9Nd0.1FeO3 thin films were prepared on Pt(111)/Ti/SiO2/Si(100) substrates by using a chemical solution deposition method. Compared to pure BiFeO3 (BFO) thin film, improved ferroelectric and leakage current properties were observed in the transition metal doped thin films. The values of remnant polarization (2P r ) and coercive electric field (2E c ) of the transition metal doped thin films were 59 μC/cm2 and 690 kV/cm at 700 kV/cm for the Ni-doped Bi0.9Nd0.1FeO3 thin film, 57 μC/cm2 and 523 kV/cm at 670 kV/cm for the Mn-doped thin film, and 85 μC/cm2 and 729 kV/cm at 700 kV/cm for the Cu-doped thin film, respectively. The 2P r values observed in the transition metal doped thin films were much larger than that of the BFO thin film, 21 μC/cm2 at 660 kV/cm. Also the 2E c values of in the transition metal doped thin films were lower than that of the BFO thin film, 749 kV/cm at 660 kV/cm. The reduced leakage current density was observed in the transition metal doped thin films, which is approximately two orders of magnitude lower than the BFO thin film, 2.6?×?10?3 A/cm2 at 100 kV/cm.  相似文献   

10.
Abstract

Submicron thick ferroelectric Ag(Ta,Nb)O3 films have been pulsed laser deposited on the bulk Pt80lr20 polycrystalline substrates. They are ferroelectric at temperatures below 125 K with the remnant polarization of 0.4 μC/cm2 @ 77K and paraelectric at higher temperatures with tanδ@ 100 kHz as low as 0.015. Extensive I-V characterization has been performed in a wide temperature range 77 K to 350 K for vertical Me/Ag(Ta,Nb)O3/Pt80Ir20 capacitive cells, where the metals Me = Pd, Au, Cr, and Al have been used as a top electrode. The electronic transport in thin Me/Ag(Ta,Nb)O3/Pt80Ir20 capacitors follows the Schottky emission mechanism with the barrier height for the Pd, Au, Cr, and Al of 0.85, 0.8, 0.74, and 0.69 eV, respectively.  相似文献   

11.
Abstract

Bi–layered ferroelectric SrBi2Ta2O9 (SBT) films were successfully prepared on Pt/Ti/SiO2/Si substrates at 650°C by a modified rf magnetron sputtering technique. The SBT films annealed for 1 h in O2 (760 torr) and again for 30 min in O2 (5 torr) at 650°C show a average grain size of about 49 nm. The SBT films annealed at 65 0°C have a remanent polarization (Pr) of 6.0 μC/cm2 and coercive field (Ec) of 36 kV/cm at an excitation voltage of 5 V. The films showed fatigue–free characteristics up to 4.0 × 1010 switching cycles under 5 V bipolar pulse. The retention characteristics of SBT films looked very promosing up to 1.0 × 105 s.  相似文献   

12.
Abstract

Pulsed UV excimer laser ablation was employed to deposit multi-axial, bi-axial and uni-axial ferroelectric compositions of PZT, bismuth titanate and lead germanate respectively. In general, a fluence lower than 2 J/cm2 caused a preferential evaporation of volatile components, resulting in stoichiometric imbalance. However, the fluences beyond 2 J/cm2 enabled the deposition of stoichiometric thin films of multi-component oxide systems. The intrinsic bombardment due to the energetic ablated species during the thin film deposition seemed to influence the composition, structure, orientation and the electrical properties. The electrical characterization of ferroelectric films indicated a dielectric constant of 800–1000, a Pr of 32μC/cm2 and Ec of 130KV/cm for polycrystalline PZT films and the corresponding quantities were measured to be 150, 7 μC/cm2 and 20 KV/cm for in-situ crystallized c-axis preferred oriented bismuth titanate films. Lead germanate thin films oriented along c-axis (003) showed a dielectric constant of 30, a Pr of 2.5 μC/cm2 and Ec of 55 KV/cm.  相似文献   

13.
Pure BiFeO3 (BFO) and rare earth (RE) ion co-doped (Bi0.9RE0.1)(Fe0.975Mn0.025)O3 (RE?=?Sm, Tb and Ho, denoted by BSFM, BTFM and BHFM) thin films were prepared on Pt(111)/Ti/SiO2/Si(100) substrates by using a chemical solution deposition method. Formations of distorted rhombohedral perovskite structure for the thin films were confirmed by using an X-ray diffraction and a Raman scattering analysis. Microstructural features for the thin films were examined by using a scanning electron microscopic analysis. Among the thin films, the lowest leakage current density of 1.22?×?10?6 A/cm2 (at 100 kV/cm), large remnant polarization (2Pr) of 72.4 μC/cm2 and low coercive field (2E c ) of 689 kV/cm (at 980 kV/cm) were measured for the BTFM thin film.  相似文献   

14.
Abstract

Highly c-axis oriented single phase Na0.5K0.5NbO3 (NKN) thin films have been deposited onto polycrystalline Pt80lr20 substrates and SiO2/Si(001) wafers using pulsed laser ablation of stoichiometric ceramic target. Strong self-assembling of NKN films along the [001] direction has been observed. Properties of NKN/Pt thin film structures have been successfully tailored by oxygen pressure control from the ferroelectric state, characterized by the remnant polarization of 12 uC/cm2, dielectric constant ? ~ 520 and tan δ ~ 0.024 @ 100 kHz, to superparaelectric state with tan δ as low as 0.003 and ? = 210 with very small 1.7% dispersion in the frequency domain 0.4–100 kHz and less than 10% variation in the temperature range 77–415 K. NKN films grown onto SiO2/Si(001) substrates show quadrupled super-lattice structure along c-axis, loss tan δ less than 0.01, and ? ~ 110 @ 1 MHz. C-V measurements for Au/NKN (270nm)/SiO2/Si MFIS-diode structure yield memory window of 3.26 V at the programmable voltage of 8 V.  相似文献   

15.
A new low-temperature processing method to prepare SrBi2Ta2O9 thin films is proposed. These thin films were prepared on Pt/Ta/SiO2/Si substrates by a sol-gel method, and their structural and electrical properties were investigated. Films were annealed before and after the top Pt electrode deposition. The first annealing was performed in a 760-Torr oxygen atmosphere at 600 °C for 30 min, and the second annealing was performed in a 5-Torr oxygen atmosphere at 600 °C for 30 min. The films were well crystallized and fine-grained after the second annealing. The electrical characteristics of the 200-nm-thick film obtained by this new process were as follows: remanent polarization, Pr = 8.5 μC/cm2; coercive field, Ec = 36 kV/cm; and leakage current density, IL = 1 × 10−7 A/cm2 (at 150 kV/cm). This process is very attractive for highly integrated ferroelectric nonvolatile memory applications. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 27–33, 1997  相似文献   

16.
Abstract

CeO2 and SrBi2Ta2O9 (SBT) thin films for MFISFET (metal-fcrroelectrics-insulator-semiconductor field effect transistor) were deposited by rf sputtering and pulsed laser deposition method, respectively. The effects of oxygen partial pressure during deposition for CeO2 films were investigated. The oxygen partial pressure significantly affected the preferred orientation, grain size and electrical properties of CeO2 films. The CeO2 thin films with a (200) preferred orientation were deposited on Si(100) substrates at 600°C. The films deposited under the oxygen partial pressure of 50 % showed the best C-V characteristics among those under various conditions. The leakage current density of films showed order of the 10?7~10?8 A/cm2 at 100 kV/cm. The SBT thin films on CeO2/Si substrate showed dense microstructure of polycrystalline phase. From the C-V characteristics of MFIS structure composed of the SBT film annealed at 800°C, the memory window width was 0.9 V at ±5 V. The leakage current density of Pt/SBT/CeO2/Si structure annealed at 800°C was 4×10?7 A/cm2 at 5 V.  相似文献   

17.
Bi3.25La0.75Ti3O12 (BLT) and V-doped BLT (BLTV) thin films were prepared on Pt/Ti/SiO2/Si substrates by a pulsed laser deposition method. The effects of V doping on ferroelectric and electrical properties were investigated by polarization-electric field hysteresis loops and leakage current-voltage measurements. BLTV single phases were confirmed by X-ray diffraction. Remnant polarization was increased and the leakage current density was decreased by V doping. The leakage current density of BLT thin films suddenly increased at 100 kV/cm while that of BLTV thin films increased at the higher electric field of 160 kV/cm. The power law relationship J α En of current density vs. applied electric field is estimated to be J αE2.0 for BLT and J αE1.0 for BLTV thin films. The leakage current of the BLT/Pt junction can be explained by space-charge-limited current. However, that of the BLTV/Pt junction was characterized by the Schottky emission behavior.  相似文献   

18.
ZnO transparent conducting thin films co-doped with aluminium and fluorine (AZO:F) were prepared on glass substrates by RF magnetron sputtering at room temperature. The effect of discharge power density on the microstructure, surface morphology, electrical and optical properties was investigated. From XRD analysis, it was revealed that the intensity of (002) favoured orientation of ZnO films increased with power density from 2.6 to 6.1?W/cm2 and then turned to a randomly orientated structure as power density continuously increased to 7.8?W/cm2. The film prepared at 6.1?W/cm2 showed a better crystallization and microstructure with larger, pyramid-like grains that were approximately 180?nm long and 90?nm wide. As a result, the electrical resistivity of the AZO:F films had a minimum of 4.1?×?10?4???cm. The improvement in the electrical resistivity of AZO:F films was due to the increase in carrier concentration from 8.8?×?1020 to 1.38?×?1021?cm?3 and the mobility from 5.8 to 11.8?cm2 V?1 s?1. The increase in carrier concentration with power density was also found to affect the optical property of the films due to the Moss-Burstein shift.  相似文献   

19.
High-dielectric-constant (Ba, Sr)TiO3 [BST] films were deposited by the liquid source chemical vapor deposition (CVD) method. The system consisted of a single-wafer, low-pressure thermal CVD reactor, a vaporizer for liquid source materials, and a shower-type gas nozzle head, giving stable BST film deposition on a 6-in. diam. substrate with uniform thickness and uniform chemical composition ratio. The source materials employed were Ba(DPM)2, Sr(DPM)2, and TiO(DPM)2 dissolved in tetrahydrofuran (THF), resulting in conformal step coverage of BST films at lowered substrate temperatures, where DPM denotes dipivaloylmethanate. Moreover, the two-step deposition technique was developed to restart protrusions formed on BST film surfaces at low temperatures, where the BST films consisted of a buffer layer and a main layer; the buffer layer was a layer about 60 Å thick of CVD-BST film annealed in N2. Thus, the two-step CVD deposition of BST films on Pt and Ru electrodes achieved an equivalent SiO2 thickness of teq ∼ 0.5 nm, a leakage current of JL ∼ 1.0 × 10−8 A/cm2 (at +1.1 V), and a dielectric loss of tan δ ∼ 0.01 at a total film thickness of 250 Å, along with conformal coverage of 80% for a trench with an aspect ratio of 0.65. Then, for BST films deposited on patterned electrodes 0.24 μm wide, 0.60 μm deep, and 0.15 μm high (each spaced by 0.14 μm), the capacitance was demonstrated to be increased without significant deterioration of the leakage current: the capacitance was increased in comparison with that for films on flat electrodes, by a factor corresponding to the increase in surface area due to sidewalls of storage-node-like pattern features. This capacitance increase reflects the most characteristic advantage of CVD, an excellent step coverage on microscopic pattern features. These electrical properties satisfy the specifications for capacitors for Gb-scale dynamic random access memories (DRAMs), giving a storage capacitance of more than 25 fF/cell for a stacked capacitor having a storage node 0.2 to 0.3 μm high. © 1998 Scripta Technica, Electr Eng Jpn, 125(1): 47–54, 1998  相似文献   

20.
PZT thin films and interlayers were fabricated by the radio frequency (r.f.) Magnetron-sputtering from the Pb1.1Zr0.53Ti0.47O3, PbO and TiO2 target. As a result of the XPS depth profile analysis, we can confirm that the substrate temperature affects the oxidation condition of each element of interlayers and the PZT film. Compared to the PZT/Pt structure, the dielectric and pyroelectric properties of PZT thin films inserted by interlayers were measured to a relatively high value. In particular, the PZT/PbO structure had the highest pyroelectric properties (P = 189.4 μC/cm2K; F D = 12.7×10−6 Pa−1/2; F V = 0.018 m2/C).  相似文献   

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