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1.
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   

2.
Nanocrystalline Y2Si2O7:Eu phosphor with an average size about 60 nm is easily prepared using silica aerogel as raw material under ultrasonic irradiation and annealing temperature at 300-600 °C and this nanocrystalline decomposes into Y2O3:Eu and silica by heat treatment at 700-900 °C. The excitation broad band centered at 283 and 254 nm results from Eu3+ substituting for Y3+ in Y2Si2O7 and Y2O3/SiO2, respectively. Compared with Y2O3:Eu/SiO2 crystalline, the PL excitation and emission peaks of Y2Si2O7:Eu nanocrystalline red-shift and lead to the enhance of its luminescence intensity due to the different chemical surroundings of Eu3+ in above nanocrystallines. The decrease of PL intensity may be ascribed to quenching effect resulting from more defects in Y2O3:Eu/SiO2 crystalline.  相似文献   

3.
In this work the Mn5Si3 and Mn5SiB2 phases were produced via arc melting and heat treatment at 1000 °C for 50 h under argon. A detailed microstructure characterization indicated the formation of single-phase Mn5Si3 and near single-phase Mn5SiB2 microstructures. The magnetic behavior of the Mn5Si3 phase was investigated and the results are in agreement with previous data from the literature, which indicates the existence of two anti-ferromagnetic structures for temperatures below 98 K. The Mn5SiB2 phase shows a ferromagnetic behavior presenting a saturation magnetization Ms of about 5.35×105 A/m (0.67 T) at room temperature and an estimated Curie temperature between 470 and 490 K. In addition, AC susceptibility data indicates no evidence of any other magnetic ordering in 4-300 K temperature range. The magnetization values are smaller than that calculated using the magnetic moment from previous literature NMR results. This result suggests a probable ferrimagnetic arrangement of the Mn moments.  相似文献   

4.
Long afterglow Sr3MgSi2O8: Eu, Dy phosphor with high brightness was prepared by sintering at high temperature and weak reductive atmosphere. The luminescent properties of this photoluminescent pigment were studied systematically by investigating concentration effects. The analytical results indicated that the main emission peaks appear at 482 nm. The excitation and emission spectra of this phosphor show that both of them are broadband. This is ascribed to the 4f7→4f65d1 transition of Eu2+ in the pigment matrix, which is in good agreement with the calculated value of 470 nm, and implies that luminescent centers Eu2+ occupy the deca-coordinated Sr2+ sites with the host of Sr3MgSi2O8.  相似文献   

5.
The Ni-Cu-Zn ferrites with different contents of Bi4Ti3O12 ceramics (1-8 wt%) as sintering additives were prepared by the usual ceramic technology and sintered at 900 °C to adapt to the low temperature co-fired ceramic (LTCC) technology. The magnetic and dielectric properties of the ferrite can be effectively improved with the effect of an appropriate amount of Bi4Ti3O12. For all samples, the ferrite sintered with 2 wt% Bi4Ti3O12 has relatively high density (98.8%) and permeability, while the ferrite with 8 wt% Bi4Ti3O12 has relatively good dielectric properties in a wide frequency range. The influences of Bi4Ti3O12 addition on microstructure, magnetic and dielectric properties of the ferrite have been discussed.  相似文献   

6.
Zn/Zn5(OH)8Cl2·H2O flower-like nanostructures was electrodeposited on the coated Zn with poly (N-methyl pyrrole) in 0.1 M Zn (NO3)2 and 0.1 M KCl solution. The morphology and the structure of the Zn/Zn5(OH)8Cl2·H2O were characterized by Field Emission Scanning Electron Microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction analysis (XRD). The FT-IR results showed special peaks at 908 and 728 cm−1 related to Zn5(OH)8Cl2·H2O. The FESEM results indicated that Zn/Zn5(OH)8Cl2·H2O consists of a flower-like nanostructure and these flower-shaped structures contain many shaped nanopetals with the thickness of 27.8 nm. The XRD result confirmed that the major phase of electrodeposited product in 0.1 M KCl as supporting electrolyte was Zn5(OH)8Cl2·H2O. The ability of PMPy to create a thin film and the existence of several pores in its matrix act as a mold for the growth of Zn/Zn5(OH)8Cl2·H2O flower-like nanostructure. The trapping of Cl and OH within pores can be considered as the reason for the formation of flowerlike Zn/Zn5(OH)8Cl2·H2O nanostructures in 0.1 M KCl.  相似文献   

7.
The electrical as well as the structural properties of La2O3 thin films on TiN substrates were investigated. Amorphous stoichiometric La2O3 thin films were grown at 300 °C via atomic layer deposition technique by using lanthanum 2,2,6,6-tetramethyl-3,5-heptanedione [La(TMHD)3] and H2O as precursors. Post-annealing of the grown film induced dramatic changes in structural and the electrical properties. Crystalline phases of the La2O3 film emerged with the increase of the post-annealing temperature. Metal-insulator-metal (MIM) capacitor was fabricated to measure the electrical properties of the grown film. The dielectric constant of the La2O3 thin films increased with annealing temperature to reach the value of 17.3 at 500 °C. The leakage current density of the film post-annealed at 400 °C was estimated to be 2.78 × 10−10 and 2.1 × 10−8 A/cm2 at ±1 V, respectively.  相似文献   

8.
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   

9.
Nanocomposite of hard (BaFe12O19)/soft ferrite (Ni0.8Zn0.2Fe2O4) have been prepared by the sol–gel process. The nanocomposite ferrite are formed when the calcining temperature is above 800 °C. It is found that the magnetic properties strongly depend on the presintering treatment and calcining temperature. The “bee waist” type hysteresis loops for samples disappear when the presintering temperature is 400 °C and the calcination temperature reaches 1100 °C owing to the exchange-coupling interaction. The remanence of BaFe12O19/Ni0.8Zn0.2Fe2O4 nanocomposite ferrite with the mass ratio of 5:1 is higher than a single phase ferrite. The specific saturation magnetization, remanence magnetization and coercivity are 63 emu/g, 36 emu/g and 2750 G, respectively. The exchange-coupling interaction in the BaFe12O19/Ni0.8Zn0.2Fe2O4 nanocomposite ferrite is discussed.  相似文献   

10.
The phase relation of LaFe11.5Si1.5 alloys annealed at different high-temperature from 1223 K (5 h) to 1673 K (0.5 h) has been studied. The powder X-ray diffraction (XRD) patterns show that large amount of 1:13 phase begins to form in the matrix alloy consisting of α-Fe and LaFeSi phases when the annealing temperature is 1423 K. In the temperature range from 1423  to 1523 K, α-Fe and LaFeSi phases rapidly decrease to form 1:13 phase, and LaFeSi phase is rarely observed in the XRD pattern of LaFe11.5Si1.5 alloy annealed at 1523 K. With annealing temperature increasing from 1573  to 1673 K, the LaFeSi phase is detected again in the LaFe11.5Si1.5 alloy, and there is La5Si3 phase when the annealing temperature reaches 1673 K. There almost is no change in the XRD patterns of LaFe11.5Si1.5 alloys annealed at 1523 K for 3-5 h. According to this result, the La0.8Ce0.2Fe11.5−xCoxSi1.5 (0≤×≤0.7) alloys are annealed at 1523 K (3 h). The analysis of XRD patterns shows that La0.8Ce0.2Fe11.5xCoxSi1.5 alloys consist of the NaZn13-type main phase and α-Fe impurity phase. With the increase of Co content from x=0 to 0.7, the Curie temperature TC increases from 180 to 266 K. Because the increase of Co content can weaken the itinerant electron metamagnetic transition, the order of the magnetic transition at TC changes from first to second-order between x=0.3 and 0.5. Although the magnetic entropy change decreases from 34.9 to 6.8 J/kg K with increasing Co concentration at a low magnetic field of 0-2 T, the thermal and magnetic hysteresis loss reduces remarkably, which is very important for the magnetic refrigerant near room temperature.  相似文献   

11.
Aminated-CoFe2O4/SiO2 magnetic nanoparticles (NPs) were prepared from primary silica particles using modified StÖber method. Glucose oxidase (GOD) was immobilized on CoFe2O4/SiO2 NPs via cross-linking with glutaraldehyde (GA). The optimal immobilization condition was achieved with 1% (v/v) GA, cross-linking time of 3 h, solution pH of 7.0 and 0.4 mg GOD (in 3.0 mg carrier). The immobilized GOD showed maximal catalytic activity at pH 6.5 and 40 °C. After immobilization, the GOD exhibited improved thermal, storage and operation stability. The immobilized GOD still maintained 80% of its initial activity after the incubation at 50 °C for 25 min, whereas free enzyme had only 20% of initial activity after the same incubation. After kept at 4 °C for 28 days, the immobilized and free enzyme retained 87% and 40% of initial activity, respectively. The immobilized GOD maintained approximately 57% of initial activity after reused 7 times. The KM (Michaelis-Menten constant) values for immobilized GOD and free GOD were 14.6 mM and 27.1 mM, respectively.  相似文献   

12.
Nano-sized magnetic Y3Fe5O12 ferrite having a high heat generation ability in an AC magnetic field was prepared by bead milling. A commercial powder sample (non-milled sample) of ca. 2.9 μm in particle size did not show any temperature enhancement in the AC magnetic field. The heat generation ability in the AC magnetic field improved with a decrease in the average crystallite size for the bead-milled Y3Fe5O12 ferrites. The highest heat ability in the AC magnetic field was for the fine Y3Fe5O12 powder with a 15-nm crystallite size (the samples were milled for 4 h using 0.1 mm? beads). The heat generation ability of the excessively milled Y3Fe5O12 samples decreased. The main reason for the high heat generation property of the milled samples was ascribed to an increase in the Néel relaxation of the superparamagnetic material. The heat generation ability was not influenced by the concentration of the ferrite powder. For the samples milled for 4 h using 0.1 mm? beads, the heat generation ability (W g−1) was estimated using a 3.58×10−4 fH2 frequency (f/kHz) and the magnetic field (H/kA m−1), which is the highest reported value of superparamagnetic materials.  相似文献   

13.
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   

14.
We report on the formation of a novel ternary compound Ce2PdIn8 that is isostructural with the heavy-fermion superconductors Ce2CoIn8 and Ce2RhIn8. Its magnetic, electrical transport and thermodynamic properties were studied on polycrystalline samples in wide ranges of temperature and magnetic field strength. The results revealed Ce2PdIn8 to be a paramagnetic Kondo lattice with a coherence temperature of about 12 K. The C/T ratio of the specific heat reaches at 350 mK a strongly enhanced magnitude of about per Ce-atom, thus clearly indicating a heavy-fermion nature of this material. Moreover, a logarithmic divergence of C/T vs. T, observed below 3 K, which is accompanied by a linear temperature dependence of the electrical resistivity below 6 K, hint at a non-Fermi liquid character of the electronic ground state in the new compound reported.  相似文献   

15.
16.
A novel synthesis method was developed for the efficient red phosphor, Eu2+-activated Sr2Si5N8, by employing the strontium acetate as both the reducing agent and strontium source. The phase purity of final product was strongly dependent on the heating rate of the precursors. Sr2Si5N8:Eu2+ (2 at%) phosphor presented a broadband excitation spectrum in the range 300–500 nm, matching well with the blue emission (400/460 nm) of current InGaN light-emitting diodes (LEDs). The red emission peaking at 619 nm gave the relatively high (about 155%) intensity compared with the Y3Al5O12 (YAG) (P46-Y3) standard phosphor. In addition, the saturated chromatic coordinates (0.638, 0.359) allowed it a promising candidate as a red phosphor in white LEDs application for illumination or display.  相似文献   

17.
Lithium borate (Li2B4O7) is a low Zeff, tissue equivalent material that is commonly used for medical dosimetry using the thermoluminescence (TL) technique. Nanocrystals of lithium borate were synthesized by the combustion method for the first time in the laboratory. TL characteristics of the synthesized material were studied and compared with those of commercially available microcrystalline Li2B4O7. The optimum pre-irradiation annealing condition was found to be 300 °C for 10 min and that of post-irradiation annealing was 300 °C for 30 min. The synthesized Li2B4O7 nanophosphor has very poor sensitivity for low doses of gamma up to 101 Gy whereas from 101 to 4.5×102 Gy this phosphor exhibits a linear response and then from 4.5×102 to 103 Gy it shows supralinearity. Thermoluminescence properties of Li2B4O7 nanophosphor doped with Cu has also been investigated in this paper. It shows low fading and a linear response over a wide range of gamma radiation from 1×102 to 5×103 Gy. Therefore the synthesized lithium borate nanophosphor doped with Cu may be used for high dose measurements of gamma radiations.  相似文献   

18.
The diamond abrasive particles were coated with the TiO2/Al2O3 film by the sol-gel technique. Compared with the uncoated diamonds, the TiO2/Al2O3 film was excellent material for the protection of the diamonds. The results showed that the incipient oxidation temperature of the TiO2/Al2O3 film coated diamonds in air atmosphere was 775 °C, which was higher 175 °C than that of the uncoated diamonds. And the coated diamonds also had better the diamond's single particle compressive strength and the impact toughness than that of uncoated diamonds after sintering at 750 °C. For the vitrified bond grinding wheels, replacing the uncoated diamonds with the TiO2/Al2O3 film coated diamonds, the volume expansion of the grinding wheels decreased from 6.2% to 3.4%, the porosity decreased from 35.7% to 25.7%, the hardness increased from 61.2HRC to 66.5HRC and the grinding ratio of the vitrified bond grinding wheels to carbide alloy (YG8) increased from 11.5 to 19.1.  相似文献   

19.
The secondary ion mass spectrum of silicon sputtered by high energy C60+ ions in sputter equilibrium is found to be dominated by Si clusters and we report the relative yields of Sim+ (1 ≤ m ≤ 15) and various SimCn+ clusters (1 ≤ m ≤ 11 for n = 1; 1 ≤ m ≤ 6 for n = 2; 1 ≤ m ≤ 4 for n = 3). The yields of Sim+ clusters up to Si7+ are significant (between 0.1 and 0.6 of the Si+ yield) with even numbered clusters Si4+ and Si6+ having the highest probability of formation. The abundances of cluster ions between Si8+ and Si11+ are still significant (>1% relative to Si+) but drop by a factor of ∼100 between Si11+ and Si13+. The probability of formation of clusters Si13+-Si15+ is approximately constant at ∼5 × 10−4 relative to Si+ and rising a little for Si15+, but clusters beyond Si15 are not detected (Sim≥16+/Si+ < 1 × 10−4). The probability of formation of Sim+ and SimCn+ clusters depends only very weakly on the C60+ primary ion energy between 13.5 keV and 37.5 keV. The behaviour of Sim+ and SimCn+ cluster ions was also investigated for impacts onto a fresh Si surface to study the effects that saturation of the surface with C60+ in reaching sputter equilibrium may have had on the measured abundances. By comparison, there are very minor amounts of pure Sim+ clusters produced during C60+ sputtering of silica (SiO2) and various silicate minerals. The abundances for clusters heavier than Si2+ are very small compared to the case where Si is the target.The data reported here suggest that Sim+ and SimCn+ cluster abundances may be consistent in a qualitative way with theoretical modelling by others which predicts each carbon atom to bind with 3-4 Si atoms in the sample. This experimental data may now be used to improve theoretical modelling.  相似文献   

20.
Physical and electrical properties of sputtered deposited Y2O3 films on NH4OH treated n-GaAs substrate are investigated. The as-deposited films and interfacial layer formation have been analyzed by using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). It is found that directly deposited Y2O3 on n-GaAs exhibits excellent electrical properties with low frequency dispersion (<5%), hysteresis voltage (0.24 V), and interface trap density (3 × 1012 eV−1 cm−2). The results show that the deposition of Y2O3 on n-GaAs can be an effective way to improve the interface quality by the suppression on native oxides formation, especially arsenic oxide which causes Fermi level pinning at high-k/GaAs interface. The Al/Y2O3/n-GaAs stack with an equivalent oxide thickness (EOT) of 2.1 nm shows a leakage current density of 3.6 × 10−6 A cm−2 at a VFB of 1 V. While the low-field leakage current conduction mechanism has been found to be dominated by the Schottky emission, Poole-Frenkel emission takes over at high electric fields. The energy band alignment of Y2O3 films on n-GaAs substrate is extracted from detailed XPS measurements. The valence and conduction band offsets at Y2O3/n-GaAs interfaces are found to be 2.14 and 2.21 eV, respectively.  相似文献   

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