首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
Titanium oxide (TiOx) thin films were deposited on the Si(100) substrates by direct-current reactive magnetron sputtering at 3-15 % oxygen flow ratios (FO2% = FO2/(FO2 + FAr) × 100%), and then annealed by rapid thermal annealing (RTA) at 350-750 °C for 2 min in air. The phase, bonding and luminescence behaviors of the as-deposited and annealed TiOx thin films were analyzed by X-ray diffraction (XRD), Raman spectroscopy and photoluminescence (PL) spectroscopy, respectively. The as-deposited TiOx films were amorphous from XRD and showed weak Raman intensity. In contrast, the distinct crystalline peaks of anatase and rutile phases were detected after RTA at 550-750 °C from both XRD and Raman spectra. A mixture of anatase and rutile phases was obtained by RTA at 3 FO2% and its amount increased with annealing temperature. Only the anatase phase was detected in the 6-15 FO2% specimens after RTA. The PL spectra of all post-annealed TiOx films showed a broad peak in visible light region. The PL peak of TiOx film at 3 FO2% at 750 °C annealing can be fitted into two Gaussian peaks at ~ 486 nm (2.55 eV) and ~ 588 nm (2.11 eV) which were attributed to deep-level emissions of oxygen vacancies in the rutile and anatase phases, respectively. The peak around 550 nm was observed at 6-15 FO2% which is attributed to electron-hole pair recombination from oxygen vacancy state in anatase phase to valence band. The variation of intensity of PL peaks is concerned with the formation of the rutile and anatase phases at different FO2% and annealing temperatures.  相似文献   

2.
The Mn-doped ZnO (Zn1 − xMnxO) thin films with manganese compositions in the range of 0-8 at.% were deposited by radio-frequency (RF) magnetron sputtering on quartz glass substrates at room temperature (RT). The influence of Mn concentration on the structural, electrical and optical properties of Zn1 − xMnxO films has been investigated. X-ray diffraction (XRD) measurements reveal that all the films are single phase and have wurtzite structure with (002) c-axis orientation. The chemical states of Mn have been identified as the divalent state of Mn2+ ions in ZnO lattice. As the content of Mn increases, the c-lattice constant and the optical band gap of the films increase while the crystalline quality deteriorates gradually. Hall-effect measurements reveal that all the films are n-type and the conductivity of the films has a severe degradation with Mn content. It is also found that the intensity of RT photoluminescence spectra (PL) is suppressed and saturates with Mn doping.  相似文献   

3.
A combustion process was used to synthesize crystalline powders of La-substituted barium chromium hexaferrites Ba1 − xLaxFe11.5Cr0.5O19 (x = 0-0.25). The structures, morphologies and ferromagnetic properties of La3+ substituted nanocomposites were characterized by powder X-ray diffractometer (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). XRD results showed that single-phase barium chromium ferrite powders was found at La content x ≤ 0.2. From the SEM, it was observed that the particles calcined at 1100 °C had a plate-like hexagonal shape. The results of magnetic mensuration revealed that both MS and HC of barium hexaferrite increased up to x = 0.1, and then decreased with the increasing of La content.  相似文献   

4.
Gd-substitution dependency on the photoluminescence in YVO4:Eu3+ films grown on Si (100) substrates have been investigated by analyzing the crystalline phase and surface morphology of the films. The substitution of Gd induced not only the change of crystallinity but also the surface roughness of the films. The change of the preferred orientation in the films can be explained on the basis of the lattice mismatch between the film and Si (100) substrate. Also, the surface roughness of the films shows the similar behavior to the grain size as a function of Gd amounts. The photoluminescence (PL) intensity obtained from the Y1 − xGdxVO4:Eu3+ films grown under optimized conditions have indicated that the PL intensity is more dependent on the surface roughness than the crystallinity of films. In particular, the incorporation of Gd into the YVO4 lattice remarkably enhanced the intensity of PL and the highest emission intensity of Y0.57Gd0.40Eu0.03VO4 film was 3.3 times higher than that of YVO4:Eu3+ film.  相似文献   

5.
Thin films of CuIn1 − xAlxSe2 were grown using a cathodic electrodeposition technique. The CuIn1 − xAlxSe2 films were electrodeposited on SnO2 coated glass from aqueous baths containing different Al contents using deposition potentials ranging from − 650 mV to − 850 mV versus a saturated calomel electrode. The electrodeposited films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays, atomic force microscopy, and UV-VIS-NIR spectroscopy. The results show that single phase CuIn1 − xAlxSe2 films with Al content x around 0.27-0.33 having good stoichiometry can be produced in the above potential range. XRD and SEM studies show that films deposited at − 650 mV and − 750 mV have good crystallinity while those grown at − 850 mV have comparatively poorer crystallinity. SEM studies show that the particle size of the films grown at − 650 and − 750 mV is in the micron range but is around 100 nm when grown at − 850 mV. Optical studies show that the optical band gap shifts with Al content from 1.21 eV for x = 0.27 to about 1.42 eV for x = 0.33. The as-grown as well as vacuum annealed films were n-type in conductivity with resistivity in the range 3-5 × 10−3 Ω cm.  相似文献   

6.
Zn1−xCoxO-diluted magnetic semiconductor bulks have been prepared by hot pressing. Mixed powders of pure ZnO and CoO were compacted under pressure of 10 MPa at the temperature of 1073 K. Then, the samples were annealed in vacuum at the temperature range from 673 K to 873 K for 10 h. The crystal structure and magnetic properties of Zn1−xCoxO bulks have been investigated by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). X-ray photoelectron spectroscopy (XPS) and was used to study chemical valence of zinc and cobalt in the samples. The results showed that Zn1−xCoxO samples had c-axis-oriented wurtzite symmetry neither cobalt nor cobalt oxide phase was found in the samples if x was less than 0.15. Zn and Co were existed in Zn0.9Fe0.1O sample in Zn2+ and Co2+ states. The results of VSM experiment proved the room temperature ferromagnetic properties (RTFP) of Co-doped ZnO samples. The saturation magnetization and the coercivity of Zn0.9Co0.1O sample, observed in the MH curve, were about 0.22 emu/g and 300 Oe, respectively.  相似文献   

7.
Nanocrystalline thin films of mixed rare earth oxides (Y1-xErx)2O3(0.1 ≤ x ≤ 1) were deposited by electron beam evaporation technique on polished fused silica glass at different substrate temperatures (200-500 °C). The effect of the substrate temperature as well as the mixing parameter (x) on the structural and optical properties of these films has been investigated by using X-ray diffraction (XRD), energy dispersive x-ray analysis and optical spectrophotometry. XRD investigation shows that mixed rare earth oxides film (Y1-xErx)2O3 grown at lower substrate temperature (Ts ≤ 300 °C) are poorly crystalline, whereas films grown at higher substrate temperatures (Ts ≥ 400 °C) tend to have better crystallinity. Furthermore, the mixing parameter (x) was found to stabilize the cubic phase over the entire of 0.1 ≤ x ≤ 1. The crystallite size of the films was found to vary in the range from 25 to 39 nm. Optical band gap of the films was deterimined by analysis of the absoprtion coeffifcient. For films deposited at different substrate temperatures direct and indirect transitions occur with energies varied from 5.29 to 5.94 eV and from 4.23 to 4.51 eV, respectively. However, films of different composition x, give optical band gap varied from 6.14 to 5.86 eV for direct transition and from 5.23 to 4.22 eV for indirect transitions. Consequently, one may conclude that it is possible to tune the energy band gap by relative fraction of constituent oxides. It was found that optical constants increase with increasing the substrate temperature. Nevertheless, the values of n and k decrease with increasing the mixing parameter, x.  相似文献   

8.
M.A. Gabal 《Materials Letters》2010,64(17):1887-4867
CuFe2  xCrxO4 (0 ≤ x ≤ 1) nanopowders were successfully synthesized by a simple method using metal nitrates and freshly extracted egg white. The resultant powders annealed at 550 °C for 2 h and were investigated by X-ray diffractometer (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM). The results revealed the formation of cubic spinel structure at Cr concentrations ≥ 0.2. In spite of the lattice constant is hardly changed with increasing of Cr content, the magnetic properties of Cr-substituted copper ferrite are strongly affected. The saturation magnetization, remanent magnetization, and coercive force were found to decrease monotonously with increasing of Cr content.  相似文献   

9.
Simultaneous measurements of electrical conductivity, the Hall coefficient, and photoluminescence (PL) spectra of ion-milled Hg1  xCdxTe films (∼ 0.30 and 0.38) were performed during post-milling ageing of the films at 293 K. In the course of the PL study, a ‘relaxation’ of the blue-shift of the PL band of ion-milled Hg0.70Cd0.30Te was observed. The relaxation was caused by the decrease of the electron concentration due to gradual disintegration of defects induced by the milling. It is shown that while ion milling substantially changes the electrical properties of Hg1 - xCdxTe, its PL spectrum in the long-term is affected insignificantly.  相似文献   

10.
Thin ferroelectric films of PLTx (Pb1−xLaxTi1−x/4O3) have been prepared by a sol-gel spin coating process. As deposited films were thermally treated for crystallization and formation of perovskite structure. Characterization of these films by X-ray diffraction (XRD) have been carried out for various concentrations of La (x = 0.04, 0.08 and 0.12) on ITO coated corning glass substrates. For a better understanding of the crystallization mechanism, the investigations were carried out on films annealed at temperatures (350, 450, 550 and 650 °C). Characterization of these films by X-ray diffraction shows that the films annealed at 650 °C exhibit tetragonal phase with perovskite structure. Atomic force microscope (AFM) images are characterized by slight surface roughness with a uniform crack free, densely packed structure. Fourier transform infrared spectra (FTIR) studies of PLTx thin films (x = 0.08) deposited on Si substrates have been carried out to get more information about the phase stabilization.  相似文献   

11.
In this paper, a series of Zn1 − xCoxO nanocrystals with different cobalt percentages were fabricated by a simple chemical method, which were intensively explored for spintronics applications. X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectrophotometer, transmission electron microscope (TEM) and vibrating sample magnetometer (VSM) were used to characterize the structures and magnetic properties of prepared samples. It was concluded that Co2+ was well inserted into ZnO wurtzite structure. The ferromagnetism of Zn1 − xCoxO nanopowders was observed at room temperature. The relation between crystallization quality and magnetism of Zn1 − xCoxO nanopowders was discussed in detail. It was demonstrated the crystallization quality of Zn1 − xCoxO nanocrystals had a strong effect on the ferromagnetism.  相似文献   

12.
Novel continuous freestanding β-SiC/SiOxCy/Cfree nanocomposite films, namely, β-SiC nano-crystals in amorphous SiOxCy and free C cluster matrix material, were fabricated by melt spinning the polycarbosilane (PCS) precursor. Effects of oxidation curing time and sintering temperatures on the photoluminescence (PL) properties of nanocomposite films were investigated. The PL spectra show two strong blue emissions at 416 nm and 435 nm, which are unchanged neither with oxygen content nor with β-SiC crystallite size. The PL intensity of the films is enhanced by increasing curing time when sintered at 1200 °C. However, a reversed trend is identified after the films were sintered at 1300 °C. Spectroscopy and microscopy studies indicate that the radiative recombination of carriers is ascribed to the oxygen mono- and di-vacancy from SiOxCy at the surfaces of β-SiC nano-crystals, whereas the photogeneration of carriers occurs in the β-SiC nano-crystals cores. The obtained results are expected to have important applications in advanced optoelectronic devices.  相似文献   

13.
A facile sonochemical approach was applied for the large scale synthesis of iron oxide magnetic nanoparticles (NPs) using inexpensive and non-toxic metal salts as reactants. The as-prepared magnetic iron oxide NPs has been characterized by XRD, TEM, EDS, and VSM. X-ray diffraction (XRD) and EDS analysis revealed that Fe3O4 NPs have been successfully synthesized in a single reaction by this simple method. Transmission electron microscopy (TEM) data demonstrated that the particles were narrow range in size distribution with 11 nm average particle size. Moreover, TEM measurements also show that the synthesized nanoparticles are almost spherical in shape. The magnetization curve from vibrating sample magnetometer (VSM) measurement shows that as-synthesized NPs were nearly superparamagnetic in magnetic properties with very low coercivity, and magnetization values were 80 emu/g, which is very near to the bulk value of iron oxide. The estimated value of mass susceptibility of as-synthesized nanoparticles is Xg = 5.71 × 10− 4 m3/kg.  相似文献   

14.
The spherical particles CdSexS1 − x with 30-80 nm in radius have been successfully prepared by the hydrothermal reaction at 200 °C. The structure characterization which has been carried out using X-ray diffraction (XRD) shows hexagonal crystal structure. Novel properties have been observed via UV-visual absorption spectra and photoluminescence (PL) spectra. The absorption shoulder and the luminescence emission peaks have been tuned by changing the mole ratio of Se in the CdSexS1 − x samples.  相似文献   

15.
Single crystalline phase lead calcium titanate (Pb1−xCaxTiO3) (PCT) thin films, with Ca2+ contents between 24 and 50 at.%, have been prepared onto Pt/(1 0 0)MgO by chemical solution deposition and rapid thermal processing. The sol-gel process used enables the synthesis of air-stable and precipitate-free solutions with high Ca2+ contents (up to 50 at.% of substitution of Pb2+ by Ca2+ in the PbTiO3 perovskite has been tested). Structure and texture of the crystalline films have been determined by X-ray diffraction (XRD), using the Bragg-Brentano geometry. Strain of the films structure has been calculated by the variance method using the 1 1 1 perovskite peak of the grazing incidence XRD patterns. Data obtained by XRD and dielectric properties measured in the PCT films are compared with those reported for bulk ceramics.  相似文献   

16.
By using a sputter-assisted chemical vapor deposition (CVD) of supermagnetron plasma, amorphous CNx:H films were deposited on the lower part of two parallel electrodes. By applying rf power to the upper electrode (UPRF) at 5 W to 800 W, polymer-like a-CNx:H films were deposited on substrates placed on the lower electrode with an rf power (LORF) of 10 W. The deposition rate increased as UPRF increased. The hardness was as low as about 6.5 GPa, which is less than that of glass (13.1 GPa). The refractive index changed only slightly as UPRF changed from 1.6 to 1.75. The FT-IR spectrum showed strong absorption bands of NH and CH bonds at high and low UPRFs, respectively. The optical band gap was as large as 2.1 to 2.5, and it decreased as UPRF increased. These a-CNx:H films showed white photoluminescence (PL) with broadband. With the increase of UPRF from 5 W to 800 W, the PL peak energy shifted down from 2.3 eV to 1.9 eV.  相似文献   

17.
Nanocrystalline magnetic particles of Ni0.7−xZn0.3CoxFe2O4 with x lying between 0.0 and 0.3 were synthesized by combustion method using metal nitrates, sucrose and polyvinyl alcohol (PVA). The synthesized powders where characterized by X-ray diffraction and Transmission electron microscopy (TEM). The average crystallite size determined from XRD data using Scherrer formula lie in the range of 20-30 nm. TEM micrographs show a well defined nano-crystallite state with an average particle size of around ~ 10 nm. The electron diffraction patterns confirm the spinel crystal structure of the ferrite. Magnetic properties measured at room temperature by vibrating sample magnetometer (VSM) reveal an increase in saturation magnetization with increase in cobalt concentration. Non-linear increase in saturation magnetization is related to surface effects and method of preparation.  相似文献   

18.
Vanadium doped ZnO thin films (Zn1 − xVxO, where = 0.05 or = 0.13) were grown on c-cut sapphire substrates using pulsed laser deposition technique. Their structure and magnetic properties were examined in relation to the doping concentration. All deposited films were highly oriented along the c-axis and exhibited ferromagnetic behavior with a Curie temperature up to 300 K. The crystal structure was found to be better for layers with lower vanadium concentration. The films had a porous fine-grained microstructure and a column-like character as the V concentration was reduced. A weak dependence of magnetization on temperature was observed. The saturation magnetization was found to be strongly dependent on the crystal structure, grain size and V-ion concentration.  相似文献   

19.
High permeability magnetic films can enhance the inductance of thin-film inductors in DC-DC converters. In order to obtain high permeability, effective uniaxial anisotropic field should be as low as possible. A multilayered technique (laminating the magnetic layers with oxide spacers) was exploited to improve the magnetic properties of thick films. The FeCoHfO/AlOx multilayered films were fabricated by dc reactive magnetron sputtering. Inserting an insulator (AlOx) layer can decrease the magneto-elastic anisotropy by reducing the residual stress of the FeCoHfO magnetic films. The anisotropic field and resistivity of the FeCoHfO/AlOx multilayered films were evidently improved by multilayered coating. With this optimum configuration of 9 layers structure [FeCoHfO (133 nm)/AlOx (10 nm)]9, low anisotropic field (HK = 65 Oe) and high resistivity (ρ ∼ 1350) μΩ cm were achieved.  相似文献   

20.
Structural and magnetic properties have been studied for polycrystalline Zn1  xTMxO films where transition metal (TM) = Fe, Cr. The Zn1  xTMxO films were prepared by the radio frequency magnetron sputtering technique on Al2O3 (001) substrates. The microstructures of the films are characterized by X-ray diffraction and X-ray photoelectron spectroscopy. TM in the films exists mainly in the form of TM2+, and the TM2+ ions have substituted for the Zn2+ ions bonded in TM-O in the ZnO lattice and do not change the wurtzite structure of ZnO. The result of magnetic measurement shows that the Zn1  xTMxO films are ferromagnetic at 5 K and 300 K respectively. Subsequently, we discuss the origin of the ferromagnetism in the films.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号