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1.
The O3 absorption coefficients for the rotational lines P(12)–P(28) of the 9.4 μm emission band of the CO2 laser are presented. Measurements were made in O3–air dilute mixtures (20–600 ppm) at 25°C and a total pressure of 1013.25 h Pa using a frequency stabilized cw CO2 laser and values have been determined with greater precision than in previously reported studies.  相似文献   

2.
Kapil Dev  E. G. Seebauer   《Surface science》2004,550(1-3):185-191
Experiments employing photoreflectance spectroscopy have uncovered band bending due to electrically active defects at the Si(1 1 1)–SiO2 interface after sub-keV Ar+ ion bombardment. The band bending of about 0.5 eV resembles that for Si(1 0 0)–SiO2, and both interfaces exhibit two kinetic regimes for the evolution of band bending upon annealing due to defects healing. The healing takes place about an order of magnitude more quickly at the (1 1 1) interface, however, probably because of less fully saturated bonding and higher compressive stress.  相似文献   

3.
We have shown that, for thermally evaporated Ta2O5 or ZrO2 thin films on Si(1 0 0), O2 annealing at 300–500 °C causes the formation of an interfacial silicon oxide layer as thin as 1–2 nm which can be interpreted in terms of their high permeability to oxygen. And we have demonstrated how useful the energy loss spectra of photoexcited electrons from core levels such as O 1s are to measure the energy bandgaps of very thin insulators. With the combination of measured bandgaps and valence band lineups determined for X-ray photoelectron spectroscopy valence band spectra, we have determined the energy band alignments of Ta2O5 and ZrO2 with Si(1 0 0) before and after the O2 annealing at 500 °C. In addition, we have demonstrated that total photoelectron yield spectroscopy provides us direct information to quantify the energy distributions of both the defect states in the high-k dielectrics and the dielectric/Si(1 0 0) interface states over nearly entire Si bandgap.  相似文献   

4.
The Y0.85Bi0.1Eu0.05V1−yMyO4 (M=Nb, P) as new near-ultraviolet excited phosphors were synthesized and their luminescence properties under 365 nm excitation were investigated in detail. It indicated that by doping small amount of P5+ into V5+ sites, the excitation intensity of charge transfer (CT) band of Bi–O (330–400 nm) was greatly improved. By substituting Nb5+ for V5+, both the CT bands of Bi–O and Eu–O (240–320 nm) were significantly enhanced. As a result, the emission intensity of Y0.85Bi0.1Eu0.05V1−yMyO4 (M=Nb, P) could be improved about 90% by doping 5 mol% P5+ and 110% by doping 5 mol% Nb5+. Comparing with the commercial Y2O2S:Eu3+ phosphors, the Y0.85Bi0.1Eu0.05V0.95M0.05O4 (M=Nb, P) phosphors exhibited excellent color purity and much higher brightness. The results showed that these Y0.85Bi0.1Eu0.05V1−yMyO4 (M=Nb, P) phosphors could be considered as promising red phosphors for application in LED.  相似文献   

5.
Characterization by Auger electron spectroscopy (AES) and Fourier transformation infrared spectroscopy (FTIR) confirms (Ta2O5)x(Al2O3)1−x alloys are homogeneous pseudo-binary alloys with increased thermal stability with respect to end member oxides, Ta2O5 and Al2O3. Capacitance–voltage (CV) and current density–voltage (JV) data as a function of temperate show that the Ta d-states of the alloys act as localized electron traps, and are at an energy approximately equal to the conduction band offset of Ta2O5 with respect to Si.  相似文献   

6.
The transmission spectra of thermally evaporated Ga50Se45S5 films were measured over the wavelength range 300–900 nm. A simple method, suggested by Swanepoel, was used for the determination of the optical constants and thickness of the films. Increasing the thickness of the film beyond 450 nm does not affect the optical constants. The dependence of the absorption coefficient on the photon energy () at the edge of the absorption band is well described by the relation hν=β(hν−Eopt)2 with an optical gap equals 2.4 eV. A good fit of the experimental points with Tauc relation indicates that non-direct transition is the most probable mechanism responsible for the photon absorption inside the investigated film.  相似文献   

7.
The optical properties of Tl4Ga3InSe8 layered single crystals have been studied by means of transmission and reflection measurements in the wavelength range of 500–1100 nm. The analysis of the room temperature absorption data revealed the presence of both optical indirect and direct transitions with band gap energies of 1.94 and 2.20 eV, respectively. Transmission measurements carried out in the temperature range of 10–300 K revealed that the rate of change of the indirect band gap with temperature is γ=−4.1×10−4 eV/K. The absolute zero value of the band gap energy was obtained as Egi(0)=2.03 eV. The dispersion of the refractive index is discussed in terms of the Wemple–DiDomenico single-effective-oscillator model. The refractive index dispersion parameters: oscillator energy, dispersion energy, oscillator strength and zero-frequency refractive index were found to be 4.10 eV, 23.17 eV, 6.21×1013 m−2 and 2.58, respectively. From X-ray powder diffraction study, the parameters of monoclinic unit cell were determined.  相似文献   

8.
Far-infrared and millimeter wave spectra of copper ion conducting crystal RbCu4Cl3+xI2−x, which has the same structure as the room temperature silver ion conductor RbAg4I5, were investigated. Broad absorption peaks observed around 40, 80, and 110–200 cm−1 at room temperature show doublet structures at low temperature; this may be attributed to the difference of local structure by chlorine and iodine ion. The 110–200 cm−1 bands seem to be symmetric breathing modes of CuX4 (X = Cl or I) tetrahedron and the frequency shift coincides with the square root of the mass ratio of conduction ions. The 80 cm−1 band seems to be Rb-X vibration in RbX6 octahedron. The 40 cm−1 band seems to be the attempt mode which is an outward motion of the mobile ion in halogen cage. The increase of the absorption intensity at the low energy side with temperature corresponds to an increase of the DC conductivity. Plasmon fitting in energy loss function spectra was attempted.  相似文献   

9.
Polycrystalline perovskite La0.67Ca0.33MnO3 was synthesized by a sol–gel method. Its adiabatic temperature change ΔTad induced by a magnetic field change was measured directly. At 268 K, near its Curie temperature TC, ΔTad of La0.67Ca0.33MnO3 induced by a magnetic field change of 2.02 T reaches 2.4 K. The latent heat Q and magnetic entropy change −ΔSM induced by a magnetic field change were calculated from the temperature dependence of ΔTad and zero-field heat capacity Cp. The maximum values of Q and −ΔSM in La0.67Ca0.33MnO3 induced by a magnetic field change of 2.02 T are 1.85 J g−1 and 6.9 J kg−1 K−1, respectively. The former is larger than the phase transition latent heat of heating or cooling, which is about 1.70 J g−1.  相似文献   

10.
D. K. Saha  K. Koga  H. Takeo 《Surface science》1998,400(1-3):134-139
The thermal parameter B for three different particle sizes of diamond samples (bulk powder 1–4 μm, fine particle 144–195 Å and cluster 55–61 Å) was determined by the grazing incidence X-ray diffraction method. The values of B were found to be in the range 0.50–0.70 Å2 for particles in the size range 195–55 Å and 0.27 Å2 for 1–4 μm. All of them are larger than that of diamond bulk. A clear size dependence of B, increasing with decreasing particle size, was found. By analysing X-ray diffraction data at several temperatures the magnitude of B was found to be due to BS (static part) instead of BT (dynamic part). The average BS values obtained were 0.04 Å2, 0.19 Å2 and 0.27 Å2 for bulk powder, fine particle and cluster samples respectively. Ultrahigh resolution transmission electron microscope (TEM) observation confirmed the presence of strain, distortion, roughness and dislocation lines in many particles. TEM images of particles indicate that the clusters were not spherical in shape; they were mostly cubiform and some were truncated prism-like polyhedral. The present study reveals that the BS component is responsible for the large B value in diamond fine particles and clusters. No clear surface local atomic distortion was found in the particles.  相似文献   

11.
In very rare circumstances, X-ray photoemission spectra of copper in spinel oxides exhibit a “negative binding energy shift”. The origin of such an anomalous XPS chemical shift was investigated. A metastable Ni0.48Co0.24Cu0.6+xMn1.68−xO4 (0 < x < 0.6) spinel was fabricated at 600 °C using a low-temperature solution technique. The binding energy of the 2p3/2 level of copper (930.8 eV) is found 1.9 eV lower than that of Cu0 (932.7 eV). XPS and EXAFS studies revealed that the post-thermal annealing between 600 and 800 °C undergoes an irreversible cubic-to-tetragonal phase transformation through oxidation–reduction reaction Cu1+ + Mn4+  Cu2+ + Mn3+, and only tetrahedral Cu1+ species in the cubic spinel shows this anomalous chemical shift. The negative shift of the core levels was correlated to an equal shift of the Cu 3d valence band levels. XPS valence bands from the samples annealed at different temperatures were compared to DOS calculations. The DOS computations were performed with FEFF-8.1 code using experimental crystal parameters established by the EXAFS analysis. It was found that the tetrahedral Cu1+ in the 600 °C annealed sample exhibits localization of the 3d orbitals showing behavior characteristic to zinc. The completely filled and isolated 3d electron shell appears as a false valence band edge in the XPS spectrum. The position of the Cu 3d, and other core levels, is established by oxygen pinning the Cu valence band levels and by the fixed value of the p–d gap characteristic to the tetrahedral copper environment in this spinel.  相似文献   

12.
The structural and optical properties of β-FeSi2 precipitates produced by ion beam synthesis have been investigated by transmission electron microscopy, photoluminescence (PL) analysis and near infrared transmission measurements. The PL spectrum of β-FeSi2 precipitates in a dislocation free sample has been observed to consist of a sharp line at 1.54 μm and a weak peak at 1.46 μm. Optical transmission measurements showed a direct band gap about 0.8 eV smaller than in continuous β-FeSi2 film. Calculation of the electronic bands of β-FeSi2 for different values of the lattice parameters indicates that this reduction can be ascribed to band distortion provided by the lattice strain.  相似文献   

13.
The magnetic properties of nanocomposite melt-spun magnets with composition Sm16−xCo68+xB16 (x=0–10, 2 at% interval) and Sm8Co92−yBy (y=10–18, 2 at% interval) have been studied systematically. Several ribbons were fabricated with a wheel speed of 50 m/s, followed by annealing in the temperature range of 700–800°C for 2.5–40 min. XRD results and magnetization versus temperature curves showed that almost all of the samples were composed of the tetragonal Sm2Co14B and rhombohedral SmCo12B6 phases which are not magnetically hard at room temperature. However, a relatively high coercivity in the range of 3.5–5.5 kOe has been obtained in these samples. The highest coercivity of 5.5 kOe and a very promising β value of −0.28%/°C were obtained in Sm8Co74B18 ribbons annealed at 750°C for 5 min. The high coercivities are attributed to the small grain size of the 2 : 14 : 1 phase, in which the large surface areas enhance its effective anisotropy, and make it uniaxial type.  相似文献   

14.
Preferred crystal orientation and low electrical resistivity are required for ZrNx films applied in electronic devices. In this paper, effects of N2:(N2+Ar) flow ratio (F(N2)) and substrate temperature on the properties of the films deposited on glass substrate by reactive dc sputtering are investigated. In a wide range of F(N2) (4–24%), the films show fcc NaCl structure. While for F(N2) in the ranges of 5–12, 12–24 and >24%, the films show (1 1 1)/(2 0 0), (1 1 1) only and amorphous structures, respectively. The electrical resistivity increases with F(N2) from 5 to 24%, and can be controlled to some extent by changing the substrate temperature.  相似文献   

15.
Nd2Fe14B Φ phase crystallites were formed in Nd16.7Fe65.5B17.8 thin films prepared by RF sputtering with subsequent heat treatment. The 2 μm-thick films were deposited onto 0.1 mm Mo sheets at an average substrate temperature (Ts) of 365°C. The enhanced magnetic properties of the magnetically anisotropic thin films were investigated using different heating rates (hr) of 10°C, 20°C, 50°C and 100°C/min in an annealing experiment. Transformation from the amorphous phase to the crystalline phase is clearly manifested by the formation of fine crystallites embedded as a columnar matrix of Nd2Fe14B phase. High-resolution scanning electron microscope data of the cross-section of the annealed films show columnar stacking of Nd2Fe14B crystallites with sizes <500 nm. Transmission electron microscope observations revealed that the microstructure of these films having out-of-plane magnetization consists of uniformly distributed Φ phase with grain size around 400 nm together with small Nd rich particles. This grain size of Φ phase is comparable to the single domain particle diameter of Nd2Fe14B. Significant change in iHc, 4πMr and 4πMs with hr was confirmed. Annealing conditions with a heating rate of 50°C/min to an annealing temperature (Ta) of 650°C for 30 min was consequently found to give optimum properties for the NdFeB thin films. The resulting magnetic properties, considered to be the effect of varying hr were iHc= 1307–1357 kA/m, 4πMr=0.78–1.06 T and 4πMs=0.81–1.07 T.  相似文献   

16.
In this work, the investigation of the interface states density and series resistance from capacitance–voltage (CV) and conductance–voltage (GV) characteristics in Au/SnO2/n-Si (MOS) structures prepared at various SnO2 layer thicknesses by spray deposition technique have been reported. It is fabricated five samples depending on deposition time. The thicknesses of SnO2 films obtained from the measurement of the oxide capacitance in the strong accumulation region for MOS Schottky diodes are 37, 79, 274, 401, and 446 Å, for D1, D2, D3, D4, and D5 samples, respectively. The CV and GV measurements of Au/SnO2/n-Si MOS structures are performed in the voltage range from −6 to +10 V and the frequency range from 500 Hz to 10 MHz at room temperature. It is observed that peaks in the forward CV characteristics appeared because of the series resistance. It has been seen that the value of the series resistance Rs of samples D1 (47 Ω), D2 (64 Ω), D3 (98 Ω), D4 (151 Ω), and D5 (163 Ω) increases with increasing the oxide layer thickness. The interface state density Dit ranges from 2.40×1013 cm−2 eV−1 for D1 sample to 2.73×1012 cm−2 eV−1 for D5 sample and increases with increasing the oxide layer thickness.  相似文献   

17.
Transparent conducting oxide thin film CdTe-doped indium oxide (In2O3) has been grown by pulsed-laser deposition from a target of CdTe powder embedded in metallic indium. The electro-optical and structural properties were investigated as a function of oxygen partial pressure (PO2) and substrate temperature (Ts). A film deposited at Ts=420 °C and PO2=4 Pa shows the minimum resistivity 7.5×10−4 Ω cm, its optical transmission is 83% and the carrier concentration was 8.9×1020 cm3. The optical band gap and the average roughness of that sample were 3.6 eV and 6.45 Å, respectively. X-ray diffraction studies indicated that the films were polycrystalline. This material is a good candidate for being used as transparent conductor in the CdTe–CdS solar cell.  相似文献   

18.
In2S3 layers have been grown by close-spaced evaporation of pre-synthesized In2S3 powder from its constituent elements. The layers were deposited on glass substrates at temperatures in the range, 200–350 °C. The effect of substrate temperature on composition, structure, morphology, electrical and optical properties of the as-grown indium sulfide films has been studied. The synthesized powder exhibited cubic structure with a grain size of 63.92 nm and S/In ratio of 1.01. The films grown at 200 °C were amorphous in nature while its crystallinity increased with the increase of substrate temperature to 300 °C. The films exhibited pure tetragonal β-In2S3 phase at the substrate temperature of 350 °C. The surface morphological analysis revealed that the films grown at 300 °C had an average roughness of 1.43 nm. These films showed a S/In ratio of 0.98 and a lower electrical resistivity of 1.28 × 103 Ω cm. The optical band gap was found to be direct and the layers grown at 300 °C showed a higher optical transmittance of 78% and an energy band gap of 2.49 eV.  相似文献   

19.
The nature of the interaction of isocyanic acid (HNCO) with the active centers at the ideal anatase TiO2 (1 0 1) surface were studied using ab initio density functional theory (DFT) method with a cluster model. Two types of adsorption of isocyanic acid are found to be likely at (1 0 1) surface – dissociative and molecular adsorption. Only molecular adsorption of HNCO leads to the direct weakening and further splitting of the NC bond, which is a necessary step for the hydrolysis of isocyanic acid. During molecular adsorption of HNCO, an energetically stable intermediate surface complex is created with an adsorption energy of −1.33 eV, in which the HNCO skeleton is changing due to new strong bonds between C–Os and N–Tis. Based on the existence of this intermediate complex a probable reaction pathway for the hydrolysis of HNCO over the ideal anatase (1 0 1) surface was developed. A surface oxygen vacancy was formed after the decomposition of the intermediate complex and CO2 desorption. Afterwards, water adsorbs at the oxygen vacancy site and NH3 is successively formed. The HNCO hydrolysis over TiO2 was found to be energetically favorable with global energy gain of about −2.08 eV.  相似文献   

20.
This study was conducted to investigate the ultraweak delayed radiochemiluminescence (RCL) spectra, kinetics and spectroscopic properties of humic acids (HAs) after γ-radiation exposure (absorbed doses of 1−10 kGy, Co-60) in model systems.

The kinetics and spectral distribution of RCL (340–650 nm) were measured using the single photon counting (SPC) method and cut-off filters.

The intensity of fluorescence (λex=390, 440, 490 and 540 nm) covering the spectral range 400–580 nm was heavily dependent on the λex and slightly increased with the absorbed dose of γ-radiation.

Absorption spectra (the range 240−800 nm) and color coefficients E2.6/4 and E4/6 of irradiated solutions indicated that post-radiative degradation/polymerization processes take place in the HA, changing their macromolecule size or properties.

Comparison of FTIR spectra and elemental analysis proved an increased O and decreased C atoms in irradiated samples. The data indicate on the radiolysis-induced degradation of native HA into fulvic-like acids with higher hydrophilicity and lower molecular size.  相似文献   


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