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1.
Amorphous titanium phosphate (Ti-P-O) films are prepared by low-pressure chemical vapor deposition (CVD) using a mixture of titanium tetrachloride (TiCl4) and trimethyl phosphite (P(O-CH3)3). Two systems are studied: one is the TiCl4/P(O-CH3)3/CO2 or the CO2 system and the other is the TiCl4/P(O-CH3)3/H2 or the H2 system. Growth and properties of the CVD Ti-P-O films are functions of deposition temperature and the CO2 and H2 inputs. The films have a higher growth rate and a lower Ti content at higher deposition temperature. A high CO2 input favors for film growth, but a high H2 flow rate is detrimental. Variations of growth rate and film composition with the CO2 and H2 inputs are rationalized by the proposed growth mechanisms. The changes in internal stress with deposition temperature and the CO2 and H2 inputs are mainly attributed to film thickness. The large difference in electrical resistivity of films of the two systems deposited at 500 °C can be related to the drift of defect protons on the oxygen sites under an electric field.  相似文献   

2.
Anomalous SiO2 films have been prepared by sputtering Si in a mixture of Ar-10% O2 at 77 K. The same sputtering conditions at room temperature yield normal SiO2 which means that the anomaly is produced by the low temperature deposition. The anomaly reveals itself in several physical properties. The density of the anomalous SiO2 is 1.72 as compared with 2.20 for bulk and the dielectric constant is about 50% larger than bulk and with a much stronger temperature dependence. The infrared (ir) spectrum of the anomalous SiO2 is only slightly different from bulk SiO2 but esr experiments reveal about 3 × 1018 spins cm which do not exist in bulk SiO2. These anomalous films are extremely stable: upon heating only a small amount of oxygen (1 part in 105) evolves at 440°C but the density and IR spectrum remain unchanged up to 1300°C. Annealing at 1500°C completely removes the ESR signal and returns the ir spectrum and the density to that of cristobalite. An electron diffraction and transmission electron microscopy study reveals that the anomalous SiO2 films consist of essentially bulk like SiO2 clusters about 250 Å in diameter separated by a low density network. The low density network undoubtedly contains unbound O atoms and the SiSi bonds which give rise to the esr signal. The structural model can account for all the anomalous properties.  相似文献   

3.
SnO2 films have been deposited on Y-stabilized ZrO2 (YSZ) (1 0 0) substrates at different substrate temperatures (500–800 °C) by metalorganic chemical vapor deposition (MOCVD). Structural, electrical and optical properties of the films have been investigated. The films deposited at 500 and 600 °C are epitaxial SnO2 films with orthorhombic columbite structure, and the HRTEM analysis shows a clear epitaxial relationship of columbite SnO2(1 0 0)||YSZ(1 0 0). The films deposited at 700 and 800 °C have mixed-phase structures of rutile and columbite SnO2. The carrier concentration of the films is in the range from 1.15×1019 to 2.68×1019 cm−3, and the resistivity is from 2.48×10−2 to 1.16×10−2 Ω cm. The absolute average transmittance of the films in the visible range exceeds 90%. The band gap of the obtained SnO2 films is about 3.75–3.87 eV.  相似文献   

4.
The ionic conductivity of evaporated Li2OB2O3 thin films has been studied. These thin films were found to show a considerably high ionic conductivity of 1 × 10?7 Ω?1 cm?1 at room temperature. The conductivity increases with increasing Li content and exhibits a maximum value near 3Li2O·B2O3. The structure of these films was determined using infrared absorption and laser Raman scattering spectroscopy. Using the results, the correlation between structure and conductivity is also discussed.  相似文献   

5.
The dc conductivity of semiconducting vanadium tellurite glasses of compositions in the range 50 to 80 mol% V2O5 has been measured in the temperature region 77 to 400 K. Measurements have been made on annealed samples at different annealing temperatures. Annealing the samples at temperature of about 250°C causes the appearance of a complex crystalline phase resulting in an increase of conductivity. Results are reported for amorphous samples of different compositions. The conductivity of tellurite glasses is slightly higher than the corresponding composition of phosphate glasses, but the general trend of the increase of conductivity and decrease of high temperature activation energy with increasing V2O5 content is similar in the two systems. The data have been analysed in the light of existing models of polaronic hopping conduction. A definite conclusion about the mechanics of conduction (adiabatic or nonadiabatic) is difficult in the absence of a precise knowledge of the characteristic phonon frequency v0. Adiabatic hopping is indicated for v0~1011 Hz, however this value leads to unreasonably low value for the Debye temperature θD, and higher values for v0~1013 hz satifiies the conditions for nonadiabatic hopping which appears to be the likely mechanism of conduction in V2O5TeO2 glasses. The low temperature data (< 100 K) can be fitted to Mott's variable range hopping, which when combined with ac conductivity data gives reasonable values of α, but a high value for the disorder energy.  相似文献   

6.
Deposition of SrTiO3 (STO) thin films by ultra-high vacuum rf magnetron sputtering was performed in order to produce high-quality STO/p-Si (1 0 0) interfaces and STO insulator layers with high dielectric constants. The deposition temperatures were in the range from room temperature to 550 °C. Capacitance-voltage (C-V) and conductance-frequency measurements showed that the dielectric constant of the films ranges from 55 to 120. C-V measurements on Al/STO/p-Si structures clearly revealed the creation of metal-insulator-semiconductor diodes. The interface state densities (Dit) at the STO/p-Si interfaces were obtained from admittance spectroscopy measurements. The samples deposited at lower temperatures revealed values of Dit between 2×1011 and 3.5×1012 eV−1 cm−2 while the higher temperature deposited samples had a higher Dit ranging between 1×1011 and 1×1013 eV−1 cm−2. The above results were also well correlated to X-ray diffraction measurements, Rutherford backscattering spectroscopy, and spectroscopic ellipsometry.  相似文献   

7.
E. Sheha 《Journal of Non》2010,356(43):2282-2285
In this work, solid acid membrane consisting of poly(vinyl alcohol) (PVA), ammonium bromide (NH4Br) and sulfuric acid (SA) has been prepared by a solution casting technique method. X-ray diffraction of the (PVA)0.75(NH4Br)0.25(H2SO4)xM polymer matrix and pure (PVA)0.75(NH4Br)0.25 revealed the difference in crystallinity between them. The effect of different amounts of SA on the conductivity of the polymer electrolytes was studied. The ionic conductivity of the prepared electrolytes can reach 3.1 × 10−2 S cm−1 at room temperature. The conductivity measurements carried out at different temperatures indicate that all the films follow Arrhenius behavior and that the activation energy decreases with the increase in SA concentration. The a.c. conductivity seems to follow the universal power law.  相似文献   

8.
Fluorinated nanoporous silica (denoted as SiO2:F) thin films with low dielectric constant were prepared by a sol-gel method and spin coating technique. The leakage current densities of the SiO2:F thin films were 10−8 and 3 × 10−6 A/cm2 respectively for the as-deposited films and for those subjected to annealing at a temperature of 450 °C. These currents are more than one order of magnitude lower than those of the common SiO2 films. Photoluminescent results showed strong blue-light emission and a small blue shift in the SiO2:F films that were related to the increment of the porosity. The dielectric properties were also characterized and the k value of the annealed SiO2:F film was found to be about 1.67. The hole size in the films is small and the size distribution is uniform for the annealed SiO2:F samples due to the effects of fluorination. The underlying mechanism for fluorination is discussed in this paper.  相似文献   

9.
The nanostructured 6CaO·6SrO·7Al2O3 (C6S6A7) thin films with cubic structure using calcium, strontium metals, aluminium isopropoxide and ethylene glycol monomethyl ether as stating materials has been fabricated via sol-gel route. Based on hydrolysis of Ca2+, Sr2+ and Al3+ in the sol-gel processing using ethylene glycol monomethyl ether as solvent have been employed as the precursor material. The films were coated on soda lime float glass by the dip coating technique and annealed at 450 °C in air atmosphere. The structure, morphology and composition of the films were investigated by Fourier transformed infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy indicating that the films were composed of C6S6A7 nanoparticles with cubic structure. The spectral transmittance of the films was measured in the wavelength range of 200-1100 nm using an UV-visible spectrometer. It has been found that the optical properties of the films significantly affected by precursor chemistry and annealing temperature due to the improvement of the crystallinity of the films with increasing annealing temperature and became stable when the annealing temperature is higher than 450 °C. The C6S6A7 films annealed at 450 °C had high transparency about 80% in wide visible range.  相似文献   

10.
Thin films of LiCoO2 were prepared by pulsed laser deposition technique and the properties were studied in relation to the deposition parameters. The films deposited from a sintered composite target (LiCoO2+Li2O) in an oxygen partial pressure of 100 mTorr and at a substrate temperature of 300 °C exhibited preferred c-axis (0 0 3) orientation perpendicular to the substrate surface. The AFM data demonstrated that the films are composed of uniform distribution of fine grains with an average grain size of 80 nm. The grain size increased with an increase in substrate temperature. The (0 0 3) orientation decreased with increase in (1 0 4) orientation for the films deposited at higher substrate temperatures (>500 °C) indicating that the films’ growth is parallel to the substrate surface. The composition of the experimental films was analyzed using X-ray photoelectron spectroscopy (XPS). The binding energy peaks of Co(2p3/2) and Co(2p1/2) are, respectively, observed at 779.3 and 794.4 eV, which can be attributed to the Co3+ bonding state of LiCoO2. The electrochemical measurements were carried out on Li//LiCoO2 cells with a lithium metal foil as anode and LiCoO2 film as cathode of 1.5 cm2 active area using a Teflon home-made cell hardware. The Li//LiCoO2 cells were tested in the potential range 2.6-4.2 V. Specific capacity as high as 205 mC/cm2 μm was measured for the film grown at 700 °C. The growth of LiCoO2 films were studied in relation to the deposition parameters for their effective utilization as cathode materials in solid-state microbattery application.  相似文献   

11.
Thin films (1-10 μm thickness) of nanocomposites (NC) based on organic coordinated compound (OCC) Eu(TTA)2(Phen3PO)2NO3 (where TTA is thenoyltrifluoroacetonate (C8H5F3O2S), Phen - 1,10-phenanthroline (C12H8N2)) and polymer - polyvinylpyrrolidone ((C6H9NO)n) (PVP)) were obtained by chemical methods. NC were characterized by measurements of optical transmission, and photoluminescence (PL) at different concentrations of Eu(TTA)2(Phen3PO)2NO3 in NC. Using the optical transmission spectra, the characteristic parameters of NC such as threshold of absorbance and the position of the absorption edge on the concentration of the OOC in NC, etc., were determined. The light displacement of threshold absorption to infrared region was observed with increasing of concentration of coordinated material in NC. It was established that the excitation spectrum at which the photoluminescence in NC take place cover the range of wavelength from 200 to 410 nm. The PL of nanocomposites was detected as specific for internal transitions 4f-4f of the Eu3+ ion 5D0  7Fi (i = 0,1,2,3 and 4) centred at 537, 580, 615, 650 and 702 nm, respectively at T = 300 K. The dominant PL was observed at 615 nm and its halfwidth is less than 10 nm. The intensity of photoluminescence at 615 nm of NC is 2 times higher than the value of intensity of PL of Eu(TTA)2(Phen3PO)2NO3 powders at equal conditions of excitation.  相似文献   

12.
The well known and characterized fast ion conducting (FIC) LiI + Li2S + GeS2 glass-forming system has been further optimized for higher ionic conductivity and improved thermal and chemical stability required for next generation solid electrolyte applications by doping with Ga2S3 and La2S3. These trivalent dopants are expected to eliminate terminal and non-bridging sulfur (NBS) anions thereby increasing the network connectivity while at the same time increasing the Li+ ion conductivity by creating lower basicity [(Ga or La)S4/2] anion sites. Consistent with the finding that the glass-forming range for the Ga2S3 doped compositions is larger than that for the La2S3 compositions, the addition of Ga2S3 is found to eliminate NBS units to create bridging sulfur (BS) units that not only gives an improvement to the thermal stability, but also maintains and in some cases increases the ionic conductivity. The compositions with the highest Ga2S3 content showed the highest Tgs of ∼325 °C. The addition of La2S3 to the base glasses, by comparison, is found to create NBS by forming high coordination octahedral LaS63− sites, but yet still improved the chemical stability of the glass in dry air and retained its high ionic conductivity and thermal stability. Significantly, at comparable concentrations of Li2S and Ga2S3 or La2S3, the La2S3-doped glasses showed the higher conductivities. The addition of the LiI to the glass compositions not only improved the glass-forming ability of the compositions, but also increased the ionic conductivity glasses. LiI concentrations from 0 to 40 mol% improved the conductivities of the Ga2S3 glasses from ∼10−5 to ∼10−3 (Ω cm)−1 and of the La2S3 glasses from ∼10−4 to ∼10−3 (Ω cm)−1 at room temperature. A maximum conductivity of ∼10−3 (Ω cm)−1 at room temperature was observed for all of the glasses and this value is comparable to some of the best Li ion conductors in a sulfide glass system. Yet these new compositions are markedly more thermally and chemically stable than most Li+ ion conducting sulfide glasses. LiI additions decreased the Tgs and Tcs of the glasses, but increased the stability towards crystallization (Tc − Tg).  相似文献   

13.
Gd2O3-doped CeO2 (Gd0.1Ce0.9O1.95, GDC) thin films were synthesized on (1 0 0) Si single crystal substrates by a reactive radio frequency magnetron sputtering technique. Structures and surface morphologies were characterized by X-ray diffraction (XRD), Atomic Force Microscopy (AFM) and one-dimensional power spectral density (1DPSD) analysis. The XRD patterns indicated that, in the temperature range of 200–700 °C, f.c.c. structured GDC thin films were formed with growth orientations varying with temperature—random growth at 200 °C, (2 2 0) textures at 300–600 °C and (1 1 1) texture at 700 °C. GDC film synthesized at 200 °C had the smoothest surface with roughness of Rrms=0.973 nm. Its 1DPSD plot was characterized with a constant part at the low frequencies and a part at the high frequencies that could be fitted by the f−2.4 power law decay. Such surface feature and scaling behavior were probably caused by the high deposition rate and random growth in the GDC film at this temperature. At higher temperatures (300–700 °C), however, an intermediate frequency slope (−γ2≈−2) appeared in the 1DPSD plots between the low frequency constant part and the high frequency part fitted by f−4 power law decay, which indicated a roughing mechanism dominated by crystallographic orientation growth that caused much rougher surfaces in GDC films (Rrms>4 nm).  相似文献   

14.
GeO2/SiO2-glasses with relatively high expansion coefficients (between 5 and 7.3 × 10?6 °C?1) were prepared by hydrolysis of metal alkoxides (tetramethoxy silane+tetraethoxy germane as well as mixtures of the silane with GeO2-powder) with subsequent heat treatment up to 1000°C. It is shown that the preparation of thin films on glasses and ceramics is possible but also that this technique can be used for liquid infiltration of porous SiC- and Si3N4-materials to increase the oxidation behaviour in the temperature range 1000 to 1400°C. In the case of molybdenumdisilicide as a ceramic material it is shown that the catastrophic inner oxidation in the low temperature range (600 to 800°C) of porous specimens (tested with plasma-sprayed MoSi2-layers on refractory metals) can be hindered if these materials are infiltrated and heat treated.  相似文献   

15.
B. Ko?cielska 《Journal of Non》2008,354(14):1549-1552
The studies of electrical conductivity of NbN-SiO2 films are reported. To obtain these films, sol-gel derived xNb2O5-(100 − x)SiO2 (where x = 100, 90, 80, 70, 60, 50 mol%) coatings were nitrided at 1200 °C. The nitridation process leads to the formation of some disordered structures, with NbN metallic grains dispersed in insulating SiO2 matrix. The structure of the samples was studied using X-ray diffraction (XRD) and atomic force microscopy (AFM). The electrical conductivity was measured with the conventional four-terminal method in the temperature range from 5 to 280 K. The superconducting transition was not observed even for the sample that does not contain silica. All the samples exhibit negative temperature coefficient of resistivity. The results of conductivity versus temperature may be described on the grounds of a model proposed for a weakly disordered system.  相似文献   

16.
Gel-glass transformation has been studied by Mössbauer spectroscopy, DTA-TG analyses and X-ray diffractometry for four compositions in the SiO2Fe2O3 system (A: 5 wt% Fe2O3, B: 10 wt% Fe2O3, C: 20 wt% Fe2O3, D: 40 wt% Fe2O3).The gels were prepared by the hydrolysis of silicon tetraethoxide and iron triethoxide and successively dried and heated in oxygen in the temperature range 40–1000°C.Samples A and B gave typical amorphous X-ray patterns up to 700°C; heating at higher temperature yielded the precipitation of quartz, cristobalite and hematite in sample A, cristobalite and hematite in sample B. Crystallization was also detected by DTA in sample A for which X-ray diffraction exhibited a larger effect.In samples C and D crystallization took place starting from 300°C with the precipitation of hematite, which remained the only crystalline phase up to 1000°C.The presence of hematite was confirmed by the obtained Mössbauer spectra which showed the characteristic sextet. The apportion of iron ions in the Fe3+ and Fe2+ oxidation states was also determined, together with the attribution of the probable coordination states for Fe3+ ions.Complex magnetic structure appeared in samples treated above 800°C.  相似文献   

17.
The conductivity of glazes consisting of SnO2 in Sb-doped BaAl-borate and BaAl-borosilicate glasses has been studied for fields in the range 102–105 V/cm at temperatures 4.2 K ? T ? 470 K. The glazes were free of mobile ions such as K, Na, Li and Pb. Conduction takes place between Sb-doped SnO2 particles concentrated in the fused contact region between the much larger glass particles. At high temperatures (300–470 K), the conductivity is thermally activated of the Frenkel-Poole type. At 77 K, both tunneling and thermally activated conductivity appear to be present.  相似文献   

18.
Single crystals of β-SiC were prepared on Si substrates at a temperature around 1390°C with the standard conditions: H2 ≈ 1 1/min, SiCl4≈3 ml/min, C3H8≈1 ml/min, deposition period≈10 min. The dependences of the growth rate and the crystallinity on the substrate temperature were studied. By detailed reflection electron diffraction analyses, the crystallinity of β-SiC with 1 μm thickness was found to be better for the layer on the (100) and (110)Si substrates than for that on the (111)Si substrate. An activation energy of 25kcal/mole was obtained for the formation of β-SiC. Optimum conditions to obtain thicker β-SiC films are discussed.  相似文献   

19.
T. Serin  N. Serin  H. Sar?  O. Pakma 《Journal of Non》2006,352(3):209-215
This study investigated the effect of the substrate temperature on the structural, optical, morphological, and electrical properties of undoped SnO2 films prepared by a spray deposition method. The films were deposited at various substrate temperatures ranging from 300-500 °C in steps of 50 °C and characterized by different optical and structural techniques. X-ray diffraction studies showed that the crystallite size and preferential growth directions of the films were dependent on the substrate temperature. These studies also indicated that the films were amorphous at 300 °C and polycrystalline at the other substrate temperatures used. Infrared and visible spectroscopic studies revealed that a strong vibration band, characteristic of the SnO2 stretching mode, was present around 630 cm−1 and that the optical transmittance in the visible region varied over the range 75-95% with substrate temperature, respectively. The films deposited at 400 °C exhibited the highest electrical conductivity property.  相似文献   

20.
On the basis of the known data on the (NH4)H2PO4-KCl-KNO3-H2O system, 65.0 × 9.0 × 8.0-mm3-large crystals of the [K0.75(NH4)0.25]H2PO4 solid solutions are grown on seed by the method of temperature decrease. It is shown that the 60.0 × 17.0 × 10.0 mm3-large KH2PO4 crystals contain impurities: 6.0 × 10−3 wt % Li and 0.1 wt % Na. __________ Translated from Kristallografiya, Vol. 50, No. 4, 2005, pp. 761–764. Original Russian Text Copyright ? 2005 by Soboleva.  相似文献   

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