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1.
Bi3.25La0.75Ti3O12 (BLT) thin films were fabricated on Pt/Ti/SiO2/Si(1 0 0) substrates by chemical solution deposition (CSD), and the dependence of ferroelectric and dielectric properties of the as-deposited BLT thin films on excess Bi content in precursor sols was studied. It is found that the prepared BLT thin film shows the best polarization-electric field, capacitance-voltage and dielectric constant (?r)-frequency characteristics, when the value of excess Bi content in precursor sols is 10%. In detail, its remnant polarization (2Pr) value is 40 μC/cm2, the capacitance tunability is 21% measured at room temperature under conditions of an applied voltage of 8 V and measurement frequency of 10 kHz, and the ?r is 696 at 100 kHz frequency.  相似文献   

2.
K0.5Bi0.5TiO3 thin films were deposited on fused quartz, n-type Si(100) and Pt/TiO2/SiO2/Si substrates by repeated coating/dying cycles. X-ray diffraction analysis shows that the films annealed at 700 °C for 10 min present perovskite phase. Atomic force microscopy reveals that the surface morphology is smooth, the grain sizes of the films on Si(100) are quite larger than on fused quartz. The capacitance-voltage hysteresis loops at various sweeping speed are collected as are polarization types. The films in the ON and OFF states are relatively stable. The films also exhibit a hysteresis loop at an applied voltage of 4 V, with a remanent polarization of 9.3 μC/cm2 and a coercive voltage of 2 V. The insulating property of negative bias voltage is better than that of positive bias voltage. The transmittance of the films is between 74 and 82% in the wavelength range of 200-2000 nm.  相似文献   

3.
Se85Te10Bi5 films of different thicknesses ranging from 126 to 512 nm have been prepared. Energy-dispersive X-ray (EDX) spectroscopy technique showed that films are nearly stoichiometric. X-ray diffraction (XRD) measurements have showed that the Se85Te10Bi5 films were amorphous. Electrical conduction activation energy (ΔEσ) for the obtained films is found to be 0.662 eV independent of thickness in the investigated range. Investigation of the current voltage (I-V) characteristics in amorphous Se85Te10Bi5 films reveals that it is typical for a memory switch. The switching voltage Vth increases with the increase of the thickness and decreases exponentially with temperature in the range from 298 to 383 K. The switching voltage activation energy (ε) calculated from the temperature dependence of Vth is found to be 0.325 eV. The switching phenomenon in amorphous Se85Te10Bi5 films is explained according to an electrothermal model for the switching process. The optical constants, the refractive index (n) and the absorption index (k) have been determined from transmittance (T) and reflectance (R) of Se85Te10Bi5 films. Allowed non-direct transitions with an optical energy gap (Egopt) of 1.33 eV have been obtained. ΔEσ is almost half the obtained value of Egopt, which suggested band to band conduction as indicated by Davis and Mott.  相似文献   

4.
PbO and PZT thin films were deposited on the p-type (1 0 0) Si substrate by the rf magnetron sputtering method with PbO and Pb1.1Zr0.53Ti0.47O3 targets for the application of the metal-ferroelectric-insulator-semiconductor (MFIS) structure. The MFIS structures with the PbO buffer layer show the good electric properties including a high memory window and a low leakage current density. The maximum value of the memory window is 2.0 V under the applied voltage of 9 V for the Pt/PZT (200 nm, 400 °C)/PbO (80 nm)/Si structures with the PbO buffer layer deposited at the substrate temperature of 300 °C. From the X-ray photoelectron spectroscopy (XPS) results, we could confirm that the substrate temperature of PbO affects the chemical states of the interface between the PbO buffer layer and Si substrate, which results in the inter-diffusion of Pb and the formation of the intermediate phases (PbSiO3). And the existence of the undesired SiO2 layer, which is the low dielectric layer, was confirmed at the surface region of the Si substrate by the XPS depth profile analysis.  相似文献   

5.
(Na0.85K0.15)0.5Bi0.5TiO3 thin films were deposited on LaNiO3(LNO)/SiO2/Si(1 0 0) and Pt/Ti/SiO2/Si(1 0 0) substrates by metal-organic decomposition, and the effects of bottom electrodes LNO and Pt on the ferroelectric, dielectric and piezoelectric properties were investigated by ferroelectric tester, impedance analyzer and scanning probe microscopy, respectively. For the thin films deposited on LNO and Pt electrodes, the remnant polarization 2Pr are about 22.6 and 8.8 μC/cm2 under 375 kV/cm, the dielectric constants 238 and 579 at 10 kHz, the dielectric losses 0.06 and 0.30 at 10 kHz, the statistic d33eff values 95 and 81 pm/V. The improved piezoelectric properties could make (Na1−xKx)0.5Bi0.5TiO3 thin film as a promising candidate for piezoelectric thin film devices.  相似文献   

6.
Amorphous Lu2O3 high-k gate dielectrics were grown directly on n-type (100) Si substrates by the pulsed laser deposition (PLD) technique. High-resolution transmission electron microscope (HRTEM) observation illustrated that the Lu2O3 film has amorphous structure and the interface with Si substrate is free from amorphous SiO2. An equivalent oxide thickness (EOT) of 1.1 nm with a leakage current density of 2.6×10−5 A/cm2 at 1 V accumulation bias was obtained for 4.5 nm thick Lu2O3 thin film deposited at room temperature followed by post-deposition anneal (PDA) at 600 °C in oxygen ambient. The effects of PDA process and light illumination were studied by capacitance-voltage (C-V) and current density-voltage (J-V) measurements. It was proposed that the net fixed charge density and leakage current density could be altered significantly depending on the post-annealing conditions and the capability of traps to trap and release charges.  相似文献   

7.
Ion beam sputtering process was used to deposit n-type fine-grained Bi2Te3 thin films on BK7 glass substrates at room temperature. In order to enhance the thermoelectric properties, thin films are annealed at the temperatures ranging from 100 to 400 °C. X-ray diffraction (XRD) shows that the films have preferred orientations in the c-axis direction. It is confirmed that grain growth and crystallization along the c-axis are enhanced as the annealing temperature increased. However, broad impurity peaks related to some oxygen traces increase when the annealing temperature reached 400 °C. Thermoelectric properties of Bi2Te3 thin films were investigated at room temperature. The Bi2Te3 thin films, including as-deposited, exhibit the Seebeck coefficients of −90 to −168 μV K−1 and the electrical conductivities of 3.92×102-7.20×102 S cm−1 after annealing. The Bi2Te3 film with a maximum power factor of 1.10×10−3 Wm−1 K−2 is achieved when annealed at 300 °C. As a result, both structural and transport properties have been found to be strongly affected by annealing treatment. It was considered that the annealing conditions reduce the number of potential scattering sites at grain boundaries and defects, thus improving the thermoelectric properties.  相似文献   

8.
The influence of substrate temperature on structural and dielectric properties of cubic pyrochlore Bi1.5Zn1.0Nb1.5O7 (BZN) thin films prepared by pulsed laser deposition process has been investigated. BZN thin films were deposited on Pt/Ti/SiO2/Si(1 0 0) substrate and in situ annealed at 700 °C. The results indicate that the substrate temperature has a significant effect on the structural and dielectric properties of BZN thin films. The films exhibit a cubic pyrochlore structure in the substrate temperature range from 550 °C to 700 °C and at the annealing temperature of 700 °C. With further increase of substrate temperature to 750 °C, the phases of Bi2O3, BiNbO4 and Bi5Nb3O15 can be detected in the XRD pattern due to the Zn loss. The dielectric constant and loss tangent of the films deposited at 650 °C are 192 and 6 × 10−4 at 10 kHz, respectively. The tunability is 10% at a dc bias field of 0.9 MV/cm.  相似文献   

9.
Thin films of BixCo2−xMnO4 (x=0, 0.1 and 0.3) were grown on quartz, LaAlO3 (LAO) and YBa2Cu3O7 (YBCO) buffer layer coated LAO substrates by pulsed laser deposition (PLD). X-ray diffraction (XRD) and Raman scattering measurements showed that the thin films exhibit single phase polycrystalline cubic spinel structure on all the substrates. Near edge X-ray absorption fine structure (NEXAFS) studies confirmed the octahedral occupancy of the substituted Bi3+ ions. Temperature dependent zero-field cooled (ZFC) magnetization measurements show the ferrimagnetic (FM) behavior (TC∼186 K) and magnetization undergoes a crossover from positive to negative, owing to the opposite contributions of magnetic moments from Co and Mn ions. A weak ferroelectric property exhibited by the films above room temperature was evidenced through the capacitance-voltage (C-V) and dielectric measurements. Magnetoelectric coupling was found to be maximum just below FM-TC.  相似文献   

10.
Metal-insulator-metal (MIM) capacitors were fabricated using ZrO2 films and the effects of structural and native defects of the ZrO2 films on the electrical and dielectric properties were investigated. For preparing ZrO2 films, Zr films were deposited on Pt/Si substrates by ion beam deposition (IBD) system with/without substrate bias voltages and oxidized at 200 °C for 60 min under 0.1 MPa O2 atmosphere with/without UV light irradiation (λ = 193 nm, Deep UV lamp). The ZrO2(∼12 nm) films on Pt(∼100 nm)/Si were characterized by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM), capacitance-voltage (C-V) and current-voltage (I-V) measurements were carried out on MIM structures. ZrO2 films, fabricated by oxidizing the Zr film deposited with substrate bias voltage under UV light irradiation, show the highest capacitance (784 pF) and the lowest leakage current density. The active oxygen species formed by UV irradiation are considered to play an important role in the reduction of the leakage current density, because they can reduce the density of oxygen vacancies.  相似文献   

11.
We report the enhancement of ferroelectric properties in vanadium-doped Bi4Ti3O12 (BIT) thin films prepared by rf magnetron sputtering method for MFM and MFIS structures. The optimal sputtering parameters of the as-deposited Bi3.9Ti2.9V0.08O12 (BTV) ferroelectric films for different depositing times were obtained. Compared to the undoped BIT, vanadium doped BIT (BTV) showed better physical and electrical characteristics. The as-deposited BTV showed a remanent polarization (2P r ) of 23 μC/cm2, higher than the value of 16 μC/cm2 for BIT, as the measured frequency was 100 kHz. For BTV thin films in the MFIS structure, the leakage current density and the memory window decreased, the change ratio of capacitance critically increased as the depositing time increased from 30 to 120 min. Regarding the measured physical properties, the micro-structure and thickness of as-deposited undoped and vanadium doped BIT thin films were obtained and compared by XRD patterns and SEM images.  相似文献   

12.
The structural, dielectric and magnetic properties of single crystalline Ba1−xBixFe0.3Zr0.7O3−δ (x=0.0-0.29) thin films have been studied. The pseudotetragonal epitaxial thin films were obtained by pulsed laser-beam deposition (PLD) on (0 0 1) SrTiO3 (STO) single-crystal substrates. The Bi substitution for the Ba ions up to an extent of x=0.18 caused a slight improvement in the leakage current properties, as well as an enhancement of the apparent dielectric constant. The saturation magnetization of the films was significantly decreased following Bi substitution. These changes were thought to be related to the increase in oxygen deficiencies in the films. The effect of the Bi substitution on the dielectric and magnetic properties was analyzed in conjunction with the change in valence value of the Fe ions.  相似文献   

13.
The effects of vanadium(V) doping into SrBi4Ti4O15 (SBTi) thin films on the structure, ferroelectric, leakage current, dielectric, and fatigue properties have been studied. X-ray diffraction result showed that the crystal structure of the SBTi thin films with and without vanadium is the same. Enhanced ferroelectricity was observed in the V-doped SrBi4Ti4O15 (SrBi4−x/3Ti4−xVxO15, SBTiV-x (x = 0.03, 0.06, and 0.09)) thin films compared to the pure SrBi4Ti4O15 thin film. The values of remnant polarization (2Pr) and coercive field (2Ec) of the SBTiV-0.09 thin film capacitor were 40.9 μC/cm2 and 105.6 kV/cm at an applied electric field of 187.5 kV/cm, respectively. The 2Pr value is over five times larger than that of the pure SBTi thin film capacitor. At 100 kHz, the values of dielectric constant and dielectric loss were 449 and 0.04, and 214 and 0.06 for the SBTiV-0.09 and the pure SBTi thin film capacitors, respectively. The leakage current density of the SBTiV-0.09 thin film capacitor measured at 100 kV/cm was 6.8 × 10−9 A/cm2, which is more than two and a half orders of magnitude lower than that of the pure SBTi thin film capacitor. Furthermore, the SBTiV-0.09 thin film exhibited good fatigue endurance up to 1010 switching cycles. The improved electrical properties may be related to the reduction of internal defects such as bismuth and oxygen vacancies with changes in the grain size by doping of vanadium into SBTi.  相似文献   

14.
Thin Cd2Nb2O7 films were grown on single-crystal p-type SiO2/Si substrates by the metallo-organic decomposition (MOD) technique. The films were investigated by X-ray diffraction, X-ray energy-dispersive spectroscopy, and field emission scanning electron microscopy, and showed a single phase (cubic pyrochlore), a crack-free spherical grain structure, and nanoparticles with a mean size of about 68 nm. A Cauchy model was also used in order to obtain the thickness and index of refraction of the stack layers (transparent layer/SiO2/Si) by spectroscopic ellipsometry (SE). The dielectric constant (K) of the films was calculated to be about 25 from the capacitance-voltage (C-V) measurements.  相似文献   

15.
The formation and optical response of VOx nanoparticles embedded in amorphous aluminium oxide (Al2O3) thin films by pulsed laser deposition is studied. The thin films have been grown by alternate laser ablation of V and Al2O3 targets, which has resulted in a multilayer structure with embedded nanoparticles. The V content has been varied by changing the number of pulses on the V target. It is found that VOx nanoparticles with dimensions around 5 nm have been formed. The structural analysis shows that the vanadium nanoparticles are oxidized, although probably there is not a unique oxide phase for each sample. The films show a different optical response depending on their vanadium content. Optical switching as a function of temperature has been observed for the two films with the highest vanadium content, at transition temperatures of about −20 °C and 315 °C thus suggesting the presence of nanoparticles with compositions V4O7 and V2O5, respectively.  相似文献   

16.
BaZr0.1Ti0.9O3 and BaZr0.2Ti0.8O3 (BZT) thin films were deposited on Pt/Ti/LaAlO3 (1 0 0) substrates by radio-frequency magnetron sputtering, respectively. The films were further annealed at 800 °C for 30 min in oxygen. X-ray diffraction θ-2θ and Φ-scans showed that BaZr0.1Ti0.9O3 films displayed a highly (h 0 0) preferred orientation and a good cube-on-cube epitaxial growth on the LaAlO3 (1 0 0) substrate, while there are no obvious preferential orientation in BaZr0.2Ti0.8O3 thin films. The BaZr0.1Ti0.9O3 films possess larger grain size, higher dielectric constant, larger tunability, larger remanent polarization and coercive electric field than that of BaZr0.2Ti0.8O3 films. Whereas, BaZr0.1Ti0.9O3 films have larger dielectric losses and leakage current density. The results suggest that Zr4+ ion can decrease dielectric constant and restrain non-linearity. Moreover, the enhancement in dielectric properties of BaZr0.1Ti0.9O3 films may be attributed to (1 0 0) preferred orientation.  相似文献   

17.
The (Pb0.90La0.10)Ti0.975O3/PbTiO3 (PLT/PT), PbTiO3/(Pb0.90La0.10)Ti0.975O3/PbTiO3 (PT/PLT/PT) multilayered thin films with a PbOx buffer layer were in situ deposited by RF magnetron sputtering at the substrate temperature of 600 °C. With this method, highly (1 0 0)-oriented PLT/PT and PT/PLT/PT multilayered thin films were obtained. The PbOx buffer layer leads to the (1 0 0) orientation of the films. The dielectric, ferroelectric and pyroelectric properties of the PLT multilayered thin films were investigated. It is found that highly (1 0 0)-oriented PT/PLT/PT multilayered thin films possess higher remnant polarization 2Pr (44.1 μC/cm2) and better pyroelectric coefficient at room temperature p (p = 2.425 × 10−8 C/cm2 K) than these of PLT and PLT/PT thin films. These results indicate that the design of the PT/PLT/PT multilayered thin films with a PbOx buffer layer should be an effective way to enhance the dielectric, ferroelectric and pyroelectric properties. The mechanism of the enhanced ferroelectric properties was also discussed.  相似文献   

18.
In this work we have compared the SiO2/SiC interface electrical characteristics for three different oxidations processes (dry oxygen, water-containing oxygen and water-containing nitrogen atmospheres). MOS structures were fabricated on 8° off-axis 4H-SiC(0 0 0 1) n- and p-type epi-wafers. Electrical characteristics were obtained by I-V measurements, high-frequency capacitance-voltage (C-V) and ac conductance (G-ω) methods. Comparing the results, one observes remarkable differences between samples which underwent different oxidation routes. Among the MOS structures analyzed, the sample which underwent wet oxidation with oxygen as carrier gas presented the higher dielectric strength and lower values of interface states density.  相似文献   

19.
Glasses with composition xBi2O3·(30−x)M2O·70B2O3 (M=Li, Na) containing 2 mol% V2O5 have been prepared over the range 0≤x≤15 (x is in mol%). The electron paramagnetic resonance spectra of VO2+ of these glasses have been recorded in the X-band (≈9.3 GHz) at room temperature (RT≈300 K). Spin Hamiltonian parameters, g, g, A, A, dipolar hyperfine coupling parameter, P, and Fermi contact interaction parameter, K, have been calculated. The molecular orbital coefficients, α2 and γ2, have been calculated by recording the optical transmission spectra. In xBi2O3·(30−x)Li2O·70B2O3 glasses there is decrease in the tetragonality of the V4+O6 complex for x up to 6 mol% whereas for x≥6 mol%, tetragonality increases. In xBi2O3·(30−x)Na2O·70B2O3 glasses there is increase in the tetragonality of the V4+O6 complex with increasing x. The 3dxy orbit expands with increase in Bi2O3:M2O ratio. Values of the theoretical optical basicity, Λth, have also been reported. The DC conductivity increases with increase in temperature. The order of conductivity is 10−5 ohm−1 m−1 at low temperature and 10−3 ohm−1 m−1 at high temperature. The DC conductivity decreases and the activation energy increases with increase in Bi2O3:M2O ratio.  相似文献   

20.
La-doped HfO2 gate dielectric thin films have been deposited on Si substrates using La(acac)3 and Hf(acac)4 (acac = 2,4-pentanedionate) mixing sources by low-pressure metal-organic chemical vapor deposition (MOCVD). The structure, thermal stability, and electrical properties of La-doped HfO2 films have been investigated. Inductive coupled plasma analyses confirm that the La content ranging from 1 to 5 mol% is involved in the films. The films show smaller roughness of ∼0.5 nm and improved thermal stability up to 750 °C. The La-doped HfO2 films on Pt-coated Si and fused quartz substrates have an intrinsic dielectric constant of ∼28 at 1 MHz and a band gap of 5.6 eV, respectively. X-ray photoelectron spectroscopy analyses reveal that the interfacial layer is Hf-based silicate. The reliable value of equivalent oxide thickness (EOT) around 1.2 nm has been obtained, but with a large leakage current density of 3 A/cm2 at Vg = 1V + Vfb. MOCVD-derived La-doped HfO2 is demonstrated to be a potential high-k gate dielectric film for next generation metal oxide semiconductor field effect transistor applications.  相似文献   

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