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1.
The crystallization of thin silicon nitride (Si3N4) films deposited on polycrystalline SiC substrates was investigated by X-ray diffractometry as a function of annealing time. The amorphous Si3N4 films were produced by means of reactive r.f. magnetron sputtering. Annealing at temperatures between 1300 and 1700 °C led to the formation of crystalline films composed of -Si3N4 and β-Si3N4. The fraction of β-Si3N4 in the films reaches approximately 40% at temperatures above 1550 °C. Both polymorphic modifications were formed simultaneously during the crystallization process. A transformation of -Si3N4 to β-Si3N4 could not be observed in the time and temperature range investigated. The crystallization process of amorphous Si3N4 can be described according to the Johnson–Mehl–Avrami–Kolmogorov (JMAK) formalism, assuming a three-dimensional, interface controlled grain growth from pre-existing nuclei. The rate constants show an Arrhenius behaviour with an activation enthalpy of approximately 5.5 eV.  相似文献   

2.
Tb3+ doped Zn2SiO4 films have been deposited on SiO2 buffered Si wafers by sol–gel method. The structures of these films have been investigated with X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The results revealed that these films were composed of nanometer-size grains with a Willemite structure and had smooth surfaces. Photoluminescence measurements of the films showed a strong emission from 5D4 to 7F5 at 544 nm. The blue emission from 5D37Fj was depressed because of cross-relaxation effect. The decay kinetics of the 5D47F5 green emission was studied and a best fitting was obtained by a double exponential function. The lifetime of the excited 5D4 state is estimated to be 5.2 ms.  相似文献   

3.
In this study, we have investigated different methods for preparation of thin films of C60 and C70-sulfur compounds. Films of good quality were obtained by reaction of amorphous C60 and C70 films with a saturated sulfur solution in toluene at 40°C or with saturated sulfur vapour at a temperature of 140°C for several hours. The quality of the fullerene-sulfur films were strongly dependent on the microstructure of the initially deposited fullerene film and the synthesis temperature. X-ray diffraction analyses showed that both methods lead to the formation of films consisting of C60S16 and C70S48 (space groups C 2/c and Amm2, respectively). C60S16 films synthesised on Al2O3(012) and Si(100) substrates were texture-free while C70S48 films typically exhibited a preferential (100) orientation. The films were also characterised by Raman and IR- spectroscopy, which confirmed that the interactions between the fullerene molecules and the S8 rings are weak. The fullerene-sulfur compounds were found to be unstable at high vacuum conditions. Both materials C60S16 and C70S48 are non-conductive at room temperature with conductivities less then 10−5 (Ω/cm).  相似文献   

4.
New materials for a transparent conducting oxide film are demonstrated. Highly transparent Zn2In2O5 films with a resistivity of 3.9 × 10−4 Ω cm were prepared on substrates at room temperature using a pseudobinary compound powder target composed of ZnO (50 mol.%) and In2O3 (50 mol.%) by r.f. magnetron sputtering. MgIn2O4---Zn2In2O5 films were prepared using MgIn2O4 targets with a ZnO content of 0–100 wt.%. The resistivity of the deposited films gradually decreased from 2 × 10−3 to 3.9 × 10−4 Ω cm as the Zn/(Mg + Zn) atomic ratio introduced into the films was increased. The greatest transparency was obtained in a MgIn2O4 film. The optical absorption edge of the films decreased as the Zn/(Mg + Zn) atomic ratio was increased, corresponding to the bandgap energy of their materials. It was found that the resistance of the undoped Zn2In2O5 films was more stable than either the undoped MgIn2O4, ZnO or In2O3 films in oxidizing environments at high temperatures.  相似文献   

5.
Thin films of SrBi4Ti4O15 (SBTi), a prototype of the Bi-layered-ferroelectric oxide family, were obtained by a soft chemical method and crystallized in a domestic microwave oven. For comparison, films were also crystallized in a conventional method at 700 °C for 2 h. Structural and morphological characterization of the SBTi thin films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. Using platinum coated silicon substrates, the ferroelectric properties of the films were determined. Remanent polarization Pr and a coercive field Ec values of 5.1 μC/cm2 and 135 kV/cm for the film thermally treated in the microwave oven and 5.4 μC/cm2 and 85 kV/cm for the film thermally treated in conventional furnace were found. The films thermally treated in the conventional furnace exhibited excellent fatigue-free characteristics up to 1010 switching cycles indicating that SBTi thin films are a promising material for use in non-volatile memories.  相似文献   

6.
Transmission electron microscopy (TEM) studies of epitaxial YBa2Cu3O7−x thin films and YBa2Cu3O7/PrBa2Cu3O7 superlattices are summarized. High-resolution imaging of cross-sections and plan views and energy-dispersive X-ray microanalysis and electron energy loss spectroscopy in the transmission electron microscope were the methods applied. In the first section results on YBa2Cu3O7−x thin films With varying oxygen stoichiometry deposited onto SrTiO3 are discussed. Then, YBa2Cu3O7/PrBa2Cu3O7 superlattices deposited onto SrTiO3 and MgO are investigated. Finally, an interface analysis of high-quality YBa2Cu3O7−x thin films deposited onto sapphire with yttrium-stabilized zirconia buffer layers is presented.  相似文献   

7.
HfO2 thin films with columnar microstructure were deposited directly on ZnS substrates by electron beam evaporation process. SiO2 thin films, deposited by reactive magnetron sputtering, were used as buffer layers, HfO2 thin films of granular microstructure were obtained on SiO2 interlayer by this process. X-ray diffraction patterns demonstrate that the as-deposited HfO2 films are in an amorphous-like state with small amount of crystalline phase while the HfO2 films annealed at 450 °C in O2 for 30 min and in Ar for 150 min underwent a phase transformation from amorphous-like to monoclinic phase. Antireflection effect in certain infrared wave band, such as 3–6 μm, 4–12 μm, 4–8 μm and 3–10 μm, can be observed, which was dependent on the thickness of thin films. The cross-sectional images of HfO2 films, obtained by field emission scanning electron microscopy, revealed that there was no distinct morphological change upon annealing.  相似文献   

8.
TiO2/SnO2 thin films with different tin atomic percentages were successfully prepared on glass substrates by the spray pyrolysis method from an alcoholic solution of TiO[C5H7O2]2 with different concentrations of SnCl4. The TiO2/SnO2 thin films prepared at 450 °C presented the anatase phase in polycrystalline configuration from %Sn = 0 in the starting solution up to %Sn = 20, at higher tin content the films present an amorphous configuration. The resulting thin films have a homogeneous surface structure with some porosity. The photocatalytical properties of the films were evaluated with the degradation of methylene blue. The products of the degradation reaction were identified by 1H nuclear magnetic resonance and the film properties were studied by atomic force microscopy, scanning electron microscopy, UV–Vis spectroscopy, and X-ray diffraction.  相似文献   

9.
Thin films of the system xAl2O3–(100 − x)Ta2O5–1Er2O3 were prepared by a sol–gel method and a dip-coating technique. The influences of the composition and the crystallization of the films on Er3+ optical properties were investigated. Results of X-ray diffraction indicated that the crystallization temperature of Ta2O5 increased from 800 to 1000 °C with increased values of x. In crystallized films, the intensities of the visible fluorescence and upconversion fluorescence tend to decrease with an increase in x values, due to the high phonon energy of Al2O3; the strongest fluorescence is observed in a crystallized film for x = 4 heat treated at 1000 °C. In amorphous films obtained by heat treatment at relatively low temperatures the Er3+ fluorescence could not be observed because strong fluorescence from organic residues remaining in the films thoroughly covered the Er3+ fluorescence. On the other hand, the Er3+ upconversion fluorescence in the amorphous films was observed to be stronger than that in the crystallized films. The strongest upconversion fluorescence is observed in an amorphous film for x = 75 heat treated at 800 °C.  相似文献   

10.
The crystallographic texture and the grain size have been measured by X-ray diffraction techniques for about 200 nm-thick Cu films sputter-deposited on amorphous Ta35Si18N47 and Ti33Si23N44 underlayers, and for comparison also on TiN underlayers and oxidized silicon, all on Si (100) substrates. The (111) texture of the as-deposited Cu films increases in the sequence TiN233Si23N4435Si18N47. Amorphous Ta35Si18N47 and Ti33Si23N44 layers evidently promote quite effectively the growth of highly (111) textured Cu films. After vacuum annealing at 450°C for 30 min the texture of Cu rises on Ti33Si23N44, falls on Ta35Si18N47, while that on TiN and on SiO2 changes little and the sequence becomes TiN235Si18N4733Si23N44. The grain size of the as-deposited Cu films increases in the sequence Ti33Si23N44235Si18N4747N53 and rises moderately upon annealing, least for TiN and most for SiO2 and Ti33Si23N44.  相似文献   

11.
A highly oriented FeO thin film was formed from a Fe3O4 thin film containing Fe nanocrystallines by post-annealing at 600°C. Fe3O4 thin films were grown on Si(100) substrates by ion beam sputter deposition under oxygen ambient. The stoichiometry of the iron oxide thin film could be precisely controlled by in situ X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) pattern of the Fe3O4 thin film grown at substrate temperature of 300°C showed a mixed phase of Fe3O4 and Fe nanocrystallines with a preferred orientation (110). However, the mixed phase was converted to a highly oriented FeO(200) phase by post-annealing at 600°C. This could be inverted as a result of Ostwald ripening of the Fe3O4 and Fe nanocrystallines.  相似文献   

12.
Tantalum oxide films have been deposited by 355 nm pulsed laser ablation of metallic Ta target in O3/O2 ambient. The structure and the composition of as-deposited and annealed films were examined by X-ray diffraction and Fourier transform infrared spectroscopy. The measurements of the current–voltage and capacitance–voltage characteristics of the Al/Ta2O5/Si capacitors were performed to reveal the electrical properties of the Ta2O5 films. The effects of annealing temperature on the characteristics of thin films have been studied. The results suggest that the films annealed above 700°C have the structure of orthorhombic β-Ta2O5, thc annealing treatment at high temperature decreases the bulk trap charge, the border trap, and the interface trap densities of as-deposited films, and improves significantly the dielectric and electrical properties of Ta2O5 film.  相似文献   

13.
为了得到最优发光的薄膜材料成分参数,采用均匀设计和二次通用旋转组合设计相结合的方法建立发光强度与薄膜中氧含量和Ce3+ 离子掺杂浓度的回归方程,并用遗传算法求其取最大值时的解。用中频反应磁控溅射技术制备了相应成分的Al2O3:Ce非晶薄膜。在320nm光激发下,获得了较理想的发射光谱,对薄膜发光机理分析表明:薄膜的光致发光来自于Ce3+ 离子的5d1激发态向基态4f1的两个劈裂能级的跃迁。发光强度强烈的依赖于薄膜的掺杂浓度和氧元素含量。XPS检测表明,Al2O3:Ce薄膜中存在Ce3+ 。Ce3+ 含量和薄膜的化学成分是通过X射线散射能谱(EDS)测量的。薄膜试样的晶体结构应用X射线衍射分析。  相似文献   

14.
We have studied the surface termination of ZnO(0001¯) films grown on Al2O3 substrates with high epitaxial quality. The structural properties of the ZnO films were investigated by X-ray scattering, revealing a predominant (0001¯)ZnO out-of-plane texture with the [112¯0]ZnO[0001]Al2O3 and [112¯0]ZnO[101¯0]Al2O3 azimuthal orientations for (112¯0)Al2O3 and(0001)Al2O3 substrates, respectively. The surface termination was determined by X-ray photoemission spectroscopy (XPS) via pyridine (C5H5N) adsorption at the ZnO surface. XPS data recorded at different temperatures after exposure to pyridine revealed that for both orientations of the Al2O3 substrates the deposited ZnO films were terminated by oxygen atoms, i.e. corresponding to a ZnO (0001¯) surface.  相似文献   

15.
This paper reports the preparation process and the long lasting phosphorescence of the Sr4Al14O25:Eu2+,Dy3+ thin films obtained by magnetron sputtering. Phosphorescence was achieved by annealing the films in reducing atmosphere. Sr4Al14O25 thin film was obtained when the films were treated at 1200 °C, while SrAl2O4 was generated as the intermediate phase during the annealing process. Sr4Al14O25:Eu2+,Dy3+ film generated an emission at 485 nm, and SrAl2O4:Eu2+,Dy3+ film showed an emission peaking at 515 nm. Afterglow characteristics were observed for both films, and Sr4Al14O25:Eu2+,Dy3+ film showed a better afterglow property than the SrAl2O4:Eu2+,Dy3+ film due to a deeper trap level and a higher trap concentration formed in the thin films.  相似文献   

16.
Ferroelectric SrBi2Ta2O9/SrBi2Nb2O9 (SBT/SBN) multilayer thin films with various stacking periodicity were deposited on Pt/TiO2/SiO2/Si substrate by pulsed laser deposition technique. The X-ray diffraction patterns indicated that the perovskite phase was fully formed with polycrystalline structure in all the films. The Raman spectra showed the frequency of the O–Ta–O stretching mode for multilayer and single layer SrBi2(Ta0.5Nb0.5)2O9 (SBNT) samples was 827–829 cm−1, which was in between the stretching mode frequency in SBT (813 cm−1) and SBN (834 cm−1) thin films. The dielectric constant was increased from 300 (SBT) to 373 at 100 kHz in the double layer SBT/SBN sample with thickness of each layer being 200 nm. The remanent polarization (2Pr) for this film was obtained 41.7 μC/cm2, which is much higher, compared to pure SBT film (19.2 μC/cm2). The coercive field of this double layer film (67 kV/cm) was found to be lower than SBN film (98 kV/cm).  相似文献   

17.
Spectrally selective Ni-Al2O3 composite films were prepared by r.f. planar magnetron sputtering using hot-pressed targets of two different compositions. The composition of the films were varied by co-sputtering the target with additional nickel pellets distributed uniformly on the target. The composition of the films were analysed by energy-dispersive X-ray analysis. Optical simulations were carried out with the experimentally measured n and k and the published n and k of the metallic substrate. R.f.-sputtered SiO2 and Al2O3 were used as antireflection coatings. From the computer optimization studies we found that = 0.94 and (100°C) = 0.07 could be obtained with 650 Å of Ni-Al2O3 (f = 0.61) antireflected with 780 Å SiO2 on a nickel-coated glass substrate. When molybdenum-coated nickel-plated stainless steel substrates were used, the films were found to be stable up to 500°C in air.  相似文献   

18.
Bi2Ti2O7 thin films have been grown directly on n-type GaAs (1 0 0) by the chemical solution decomposition technique. X-ray diffraction analysis shows that the Bi2Ti2O7 thin films are polycrystalline. The optical properties of the thin films are investigated using infrared spectroscopic ellipsometry (3.0–12.5 μm). By fitting the measured ellipsometric parameter (Ψ and Δ) data with a three-phase model (air/Bi2Ti2O7/GaAs), and Lorentz–Drude dispersion relation, the optical constants and thickness of the thin films have been obtained simultaneously. The refractive index and extinction coefficient increase with increasing wavelength. The fitted plasma frequency ωp is 1.64×1014 Hz, and the electron collision frequency γ is 1.05×1014 Hz, and it states that the electron average scattering time is 0.95×10−14 s. The absorption coefficient variation with respect to increasing wavelength has been obtained.  相似文献   

19.
We report on epitaxial {1 0 0} K1−xRbxTiOPO4 waveguide films for the visible spectral range grown on KTiOPO4 substrates by liquid phase epitaxy. Using the m-line technique a refractive index increase of Δnx≈0.007 and Δnz≈0.004 for TM and TE polarisation has been determined for a K0.78Rb0.22TiOPO4 film. Optical transmission and nearfield distribution are comparable to conventional ion-exchanged waveguides. Typical attenuation of about 1 dB/cm for both TM and TE polarisation was obtained at λ=532 and 1064 nm. Energy-dispersive X-ray spectrometry reveals solid-solution films with graded rubidium composition profiles. X-ray rocking curve analyses confirm the epitaxial growth process and indicate perfect and relaxed K1−xRbxTiOPO4 films. Atomic force microscopy investigations reveal regular step structures with step heights Δh<1.3 nm resulting in rms-roughness values of ≈0.4 nm.  相似文献   

20.
The average grain size and strain in the direction parallel to the surface of thin Ni0.8Fe0.2 and Cu films, sandwiched between Ta layers, have been determined as a function of layer thickness by grazing incidence X-ray diffraction. The in-plane grain size and grain size distribution were also assessed by plan-view transmission electron microscopy. Standard θ-2θ X-ray powder diffraction was used to determine the uniform strain in the direction perpendicular to the surface. Both for Ni0.8Fe0.2 and Cu, an elongation of the lattice parameter perpendicular to the surface and a compression of the lattice parameter in the plane of the film is observed, which decreases with increasing film thickness. Additionally, for Ni0.8Fe0.2 a non-uniform elongation of the perpendicular interactomic distance at the Ta interfaces is deduced by fitting a kinematical model to the θ-2θ diffraction spectrum. This study illustrates the strength and the complementary character of standard powder X-ray diffraction, grazing incidence X-ray diffraction and transmission electron microscopy for the structural analysis of thin metal films.  相似文献   

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