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1.
WOx films were prepared by reactive dc magnetron sputtering using tungsten target. Sputtering was carried out at a total pressure of 1.2 Pa using a mixture of argon plus oxygen in an effort to determine the influence of the oxygen partial pressure on structural and optical properties of the films. The deposition rate decreases significantly as the surface of the target is oxidized. X-Ray diffraction revealed the amorphous nature of all the films prepared at oxygen partial pressures higher than 1.71×10−3 Pa. For higher oxygen partial pressures, fully transparent films were deposited, which showed a slight increase in optical band gap with increasing oxygen partial pressure, while the refractive index was simultaneously decreased.  相似文献   

2.
We describe the structural properties and electrical characteristics of thin thulium oxide (Tm2O3) and thulium titanium oxide (Tm2Ti2O7) as gate dielectrics deposited on silicon substrates through reactive sputtering. The structural and morphological features of these films were explored by X-ray diffraction, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and atomic force microscopy, measurements. It is found that the Tm2Ti2O7 film annealed at 800 °C exhibited a thinner capacitance equivalent thickness of 19.8 Å, a lower interface trap density of 8.37 × 1011 eV−1 cm−2, and a smaller hysteresis voltage of ∼4 mV than the other conditions. We attribute this behavior to the Ti incorporated into the Tm2O3 film improving the interfacial layer and the surface roughness. This film also shows negligible degrees of charge trapping at high electric field stress.  相似文献   

3.
Ho3Fe5O12 ceramics with garnet structure were prepared by the solid-state reaction method. The results revealed the existence of Fe2+ ions have intensive influence on dielectric and magnetic properties of Ho3Fe5O12 ceramics, which could be further confirmed by oxygen treatment. With a magnetic field lower than 10 kOe, the ME coefficient reaches 33 ps m−1 at room temperature. And the ME coupling was further verified by dielectric anomaly near Néel temperature.  相似文献   

4.
The luminescence properties of Ce3+ in La3F3[Si3O9] are reported. Excitation and emission bands corresponding to 4f1→5d1 transitions of Ce3+ were identified. The center of gravity of the 5d states lies at remarkable high energy (43.2×103 cm−1) for Ce3+ in a silicate compound. This high value is attributed to the combined oxygen/fluoride coordination of the Ce3+ ion. Emission from the lowest 4f5d level to the 2F5/2 and 2F7/2 levels was found at 32.4×103 and 30.4×103 cm−1. These results are compared with literature data on silicates and fluorides. From the values found for Ce3+, predictions are made for the positions of the 4f5d bands of Pr3+ and Er3+ in La3F3[Si3O9]. For both ions, it is concluded that in this host lattice emission is expected from high lying 4fn energy levels.  相似文献   

5.
We report on the growth of cubic spinel ZnCo2O4 thin films by reactive magnetron sputtering and bipolarity of their conduction type by tuning of oxygen partial pressure ratio in the sputtering gas mixture. Crystal structure of zinc cobalt oxide films sputtered in an oxygen partial pressure ratio of 90% was found to change from wurtzite Zn1−xCoxO to spinel ZnCo2O4 with an increase of the sputtering power ratio between the Co and Zn metal targets, DCo/DZn, from 0.1 to 2.2. For a fixed DCo/DZn of 2.0 yielding single-phase spinel ZnCo2O4 films, the conduction type was found to be dependent on the oxygen partial pressure ratio: n-type and p-type for the oxygen partial pressure ratio below ∼70% and above ∼85%, respectively. The electron and hole concentrations for the ZnCo2O4 films at 300 K were as high as 1.37×1020 and 2.81×1020 cm−3, respectively, with a mobility of more than 0.2 cm2/V s and a conductivity of more than 1.8 S cm−1.  相似文献   

6.
The structural, electronic and thermodynamic properties of cubic Zn3N2 under hydrostatic pressure up to 80 GPa are investigated using the local density approximation method with pseudopotentials of the ab initio norm-conserving full separable Troullier-Martin scheme in the frame of density functional theory. The structural parameters obtained at ambient pressure are in agreement with experimental data and other theoretical results. The change of bond lengths of two different types of Zn-N bond with pressure suggests that the tetrahedral Zn-N bond is slightly less compressible than the octahedral bond. By fitting the calculated band gap, the first and second order pressure coefficients for the direct band gap ofthe Zn3N2 were determined to be 1.18×10−2 eV/GPa and −2.4×10−4 eV/(GPa)2, respectively. Based on the Mulliken population analysis, Zn3N2 was found to have a higher covalent character with increasing pressure. As temperature increases, heat capacity, enthalpy, product of temperature and entropy increase, whereas the Debye temperature and free energy decrease. The present study leads to a better understanding of how Zn3N2 materials respond to compression.  相似文献   

7.
Neodymium doped strontium gallogermanate crystals were grown successfully by the Bridgman technique. The linear thermal expansion coefficients for the c- and a-axes were measured as 5.8 × 10−6 °C−1 and 6.5 × 10−6 °C−1. Absorption spectra, and fluorescence spectra, as well as fluorescence decay curves of Nd3+-doped Sr3Ga2Ge4O14 crystal, have been recorded at room temperature and used to calculate the absorption and stimulated emission cross-sections. Based on the Judd-Ofelt theory, three intensity parameters were obtained. The luminescent quantum efficiency of the 4F3/2 level was determined to be approximately 73.8% for this material. Compared with other Nd3+-doped laser crystals, Nd3+-doped Sr3Ga2Ge4O14 crystal displays special laser properties due to its disorder structure.  相似文献   

8.
(In1−xFex)2O3 (x = 0.02, 0.05, 0.2) powders were prepared by a solid state reaction method and a vacuum annealing process. A systematic study was done on the structural and magnetic properties of (In1−xFex)2O3 powders as a function of Fe concentration and annealing temperature. The X-ray diffraction and high-resolution transmission electron microscopy results confirmed that there were not any Fe or Fe oxide secondary phases in vacuum-annealed (In1−xFex)2O3 samples and the Fe element was incorporated into the indium oxide lattice by substituting the position of indium atoms. The X-ray photoelectron spectroscopy revealed that both Fe2+ and Fe3+ ions existed in the samples. Magnetic measurements indicated that all samples were ferromagnetic with the magnetic moment of 0.49-1.73 μB/Fe and the Curie temperature around 783 K. The appearance of ferromagnetism was attributed to the ferromagnetic coupling of Fe2+ and Fe3+ ions via an electron trapped in a bridging oxygen vacancy.  相似文献   

9.
This paper reports the growth and spectroscopic characterization of Er3+:Sr3Y(BO3)3 crystal. Er3+:Sr3Y(BO3)3 crystal with dimensions up to ∅20×35 mm3 has been grown by Czochralski method. The polarized spectroscopic properties of Er3+:Sr3Y(BO3)3 crystal were investigated. Based on the Judd-Ofelt theory, the effective intensity parameters Ωt were obtained: Ω2=1.71×10−20 cm2, Ω4=1.39×10−20 cm2, Ω6=0.74×10−20 cm2 for π-polarization, and Ω2=1.77×10−20 cm2, Ω4=1.44×10−20 cm2, Ω6=0.65×10−20 cm2 for σ-polarization. The emission cross-section σem was calculated to be 4.75×10−21 cm2 for π-polarization at 1536 nm and 6.30×10−21 cm2 for σ-polarization at 1537 nm. The investigated results showed that Er3+:Sr3Y(BO3)3 crystal may be regarded as a potential laser host material for 1.55 μm IR solid-state lasers.  相似文献   

10.
采用sol-gel法在Pt/TiO2/SiO2/p-Si(100)衬底上制备了Bi3.25La0.75Ti3O12(BLT)铁电薄膜,研究了在750 ℃时不同退火气压(pO2:10-4—3 atm)对薄膜微观结构和电学性能的影响.XRD和拉曼光谱结果表明在10-4和3 atm氧气压下退火 关键词: 3.25La0.75Ti3O12')" href="#">Bi3.25La0.75Ti3O12 铁电性能 sol-gel法 正交化度  相似文献   

11.
(Mg0.476Mn0.448Zn0.007)(Fe1.997Ti0.002)O4 nanocrystalline powder prepared by high energy ball-milling process were consolidated by microwave and conventional sintering processes. Phases, microstructure and magnetic properties of the ferrites prepared by different processes were investigated. The (Mg0.476Mn0.448Zn0.007)(Fe1.997Ti0.002)O4 nanocrystalline powder could be prepared by high energy ball-milling process of raw Fe3O4, MnO2, ZnO, TiO2 and MgO powders. Prefired and microwave sintered ferrites could achieve the maximum density (4.86 g/cm−3), the average grain size (15 μm) was larger than that (10 μm) prepared by prefired and conventionally sintered ferrites with pure ferrite phase, and the saturation magnetization (66.77 emu/g) was lower than that of prefired and conventionally sintered ferrites (88.25 emu/g), the remanent magnetization (0.7367 emu/g) was higher than that of prefired and conventionally sintered ferrites (0.0731 emu/g). Although the microwave sintering process could increase the density of ferrites, the saturation magnetization of ferrites was decreased and the remanent magnetization of ferrites was also increased.  相似文献   

12.
Bifunctional magnetic-optical Fe3O4/ZnO nanocomposites with different molar ratio were successfully synthesized by a facile two-step strategy. Compared with the other methods, it was found to be mild, inexpensive, green, convenient and efficient. Fe3O4 nanocrystal was used as seed for the deposit and growth of ZnO nanoparticle. A series of the characterizations manifested that the combination of Fe3O4 with ZnO nanoparticles was successful. Photocatalytic activity studies confirmed that as-prepared nanocomposites had excellent photodegradating behavior to Methyl Orange (MO) compared to the pure ZnO nanoparticles. The results showed that the degradation percentage of MO was about 93.6% for 1 h when the amount of catalyst was 0.51 g L−1 and initial concentration of MO was 6 × 10−5 mol L−1 in the pH 7 solution. Moreover, the kinetics of photocatalytic degradation reaction could be expressed by the first-order reaction kinetic model. Furthermore, the Fe3O4/ZnO nanocomposites could be also served as convenient recyclable photocatalysts because of their magnetic properties.  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.
An electronically conducting nanomaterial was synthesized by nanocrystallization of a 90V2O5·10P2O5 glass and its electrical properties were studied in an extended temperature range from − 170 to + 400 °C. The conductivity of the prepared nanomaterial reaches 2 ? 10− 1 S cm− 1 at 400 °C and 2 ? 10− 3 S cm− 1 at room temperature. It is higher than that of the original glass by a factor of 25 at room temperature and more than 100 below − 80 °C. A key role in the conductivity enhancement was ascribed to the material's microstructure, and in particular to the presence of the large number of small (ca. 20 nm) grains of crystalline V2O5. The observed conductivity dependencies are discussed in terms of the Mott's theory of the electronic hopping transport in disordered systems. Since V2O5 is known for its ability to intercalate lithium, the presented results might be helpful in the development of cathode materials for Li-ion batteries.  相似文献   

15.
Y2O3 transparent ceramics with different Nd concentration (0.1-7.0at%) were fabricated using ZrO2 as additive. All the samples exhibit high transparency over a broad spectral region. The elements (Y, O and Nd) are uniformly distributed in the ceramic body, and the average grain size increases with Nd content. Based on the absorption spectrum, the Judd-Ofelt intensity parameters are calculated (Ω2=4.364×10−20 cm2, Ω4=3.609×10−20 cm2 and Ω6=2.919×10−20 cm2). The absorption coefficients increase linearly with Nd3+ doping concentration. The absorption cross-section at 804 nm and stimulated emission cross-section at 1078 nm are calculated to be 1.54×10−20 and 7.24×10−20 cm2, respectively. All the emission bands exhibit the highest emission intensities with 1.0at% Nd3+ ion content, while the lifetime decreases dramatically from 321.5 μs (0.1at% Nd) to 17.9 μs (7.0at% Nd). According to the emission spectra and measured lifetime, the optimum doping concentration of Nd3+ ion in Y2O3 transparent ceramic might be around 1.0at%.  相似文献   

16.
The [TMA]2Zn0.5Cu0.5Cl4 hybrid material was prepared and its dielectric spectra were measured in the 10−1 Hz-106 Hz frequency range and 200-305 K temperature interval. The dielectric permittivity showed a ferroelectric-paraelectric phase transition at 293 K. Double relaxation peaks are observed in the imaginary part of the electrical modulus, suggesting the presence of grain and grain boundary in the sample. The frequency dependent conductivity was interpreted in term of Jonscher's law: σ(ω)=σdc+n. The temperature dependent of the dc conductivity (σdc) was well described by the Arrhenius equation: σdcT=σo×exp(−Ea/kT).  相似文献   

17.
We present new experimental data on the collision-induced fundamental absorption in N2-H2 mixtures at room temperature and at low enough pressures so that the binary contribution is dominant. Previous measurements have been made at pressures where the ternary and possibly higher absorption coefficients are significant, and this makes it difficult to obtain accurate values for the binary absorption enhancement coefficient. To obtain the enhancement spectrum from the measurements of the mixture, it is necessary to subtract out both the spectra of pure H2 and N2, along with some CO2 impurities thus increasing the experimental uncertainty. Nevertheless, we obtain a value for the integrated intensity of 1.15×10−4 cm−2 amagat−2 that is in good agreement with the previous value of 1.38×10−4. We also discuss how one can scale this result to high temperatures for application to brown dwarf or methane dwarf atmospheres.  相似文献   

18.
Tb3+-doped Sr3(PO4)2 phosphor was prepared by a sol-gel combustion method. A trigonal structure having Sr and O atoms occupying two different lattice sites were obtained. Scanning Auger nanoprobe was used to analyze the morphology of the particles. Photoluminescence (PL) and cathodoluminescence (CL) properties of Sr3(PO4)2:Tb powder phosphors were evaluated and compared. In addition, the CL intensity degradation of Sr3(PO4)2:Tb was evaluated when the powders were irradiated with a beam of electrons in a vacuum chamber maintained at an O2 pressure of 1 × 10−6 Torr or a background pressure of 1 × 10−8 Torr O2. The surface chemical composition of the degraded powders, analyzed by X-ray photoelectron spectroscopy (XPS), suggests that new compounds (metal oxides) of strontium and phosphorous were formed on the surface. It is most likely that these compounds contributed to the CL intensity degradation of the Sr3(PO4)2:Tb phosphors. The CL properties and possible mechanism by which the new metal oxides were formed on the surface due to a prolonged electron beam irradiation are discussed.  相似文献   

19.
The microstructure and magnetic properties have been investigated systematically for Sn1−xMnxO2 polycrystalline powder samples with x=0.02-0.08 synthesized by a solid-state reaction method. X-ray diffraction revealed that all samples are pure rutile-type tetragonal phase and the cell parameters a and c decrease monotonously with the increase in Mn content, which indicated that Mn ions substitute into the lattice of SnO2. Magnetic measurements revealed that all samples exhibit room temperature ferromagnetism. Furthermore, magnetic investigations demonstrate that magnetic properties strongly depend on doping content, x. The average magnetic moment per Mn atom decreases with increase in the Mn content, because antiferromagnetic super-exchange interaction takes place within the neighbor Mn3+ ions through O2− ions for the samples with higher Mn doping. Our results indicate that the ferromagnetic property is intrinsic to the SnO2 system and is not a result of any secondary magnetic phase or cluster formation.  相似文献   

20.
Ta2O5 films were deposited on BK7 substrates by e-beam evaporation with different deposition parameters such as substrate temperature (323-623 K), oxygen pressure (0.5-3.0×10−2 Pa) and deposition rate (0.2-0.5 nm/s). Absorption, scattering and chemical composition were investigated by surface thermal lensing (STL) technique, total integrated scattering (TIS) measurement and X-ray photoelectron spectroscopy (XPS), respectively. The laser-induced damage threshold (LIDT) was assessed using pulsed Nd:YAG 1064 nm laser at a pulse length of 12 ns. The results showed that optical properties, absorption and LIDT were influenced by the deposition parameters and annealing. However, scattering was little correlated with the deposition parameters. On the whole, the LIDT increased with increasing substrate temperature and oxygen pressure, whereas it increased firstly and then decreased upon increasing deposition rate. After annealing at 673 K for 12 h, the LIDT of films improved significantly. The dependence of possible damage mechanism on deposition parameters was discussed.  相似文献   

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