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1.
Thin films of CdxSe1−x (0<x<1) have been deposited by the vacuum evaporation technique onto ultra clean substrates maintained at 300°C. The optical properties (specially transmission spectra) of these films were studied. The wavelength dependence of refractive index and extinction coefficient of the films along with the variation of these constants with composition was studied. 相似文献
2.
S. Seiro G. Remnyi M. Saint-Paul H. R. Salva A. A. Ghilarducci P. Monceau P. Ljay 《Materials Science and Engineering: A》2004,370(1-2):384-387
Manganese oxides with distorted perovskite structure have attracted much attention during the last decade due to their colossal magnetoresistance (CMR), and the strong correlations among the various degrees of freedom involved. In particular, Pr1−xCaxMnO3 compounds present in a wide Ca-doping range a charge ordering phenomenon, consisting of real space ordering of Mn3+ and Mn4+ in alternate lattice sites below a certain temperature TCO. This ordering brings about a lattice distortion and a large hardening of the sound velocity below TCO. Tomioka et al. have observed that an applied magnetic field can melt this charge ordered state and induce a transition from an insulating to a metallic state. In order to study the effects of this charge order melting, ultrasonic longitudinal sound velocity measurements were performed on polycrystalline Pr1−xCaxMnO3 (x=0.35 and 0.5) as a function of magnetic field and temperature. Interesting anomalies were found related to the melting of the charge ordered phase into a metal-like state even at low temperatures. 相似文献
3.
Optical constants of vacuum-evaporated thin films in the Ge1 − xSe2Pbx (x = 0, 0.2, 0.4, 0.6) system were calculated from reflectance and transmittance spectra. It is found that the films exhibit a non-direct gap, which decreases with increasing Pb content. The variation in the refractive index and the imaginary part of the dielectric constant with photon energy is reported. The relationship between the optical gap and chemical composition in chalcogenide glasses is discussed in terms of the average heat of atomization. 相似文献
4.
The phase relations in CeO2–Eu2O3 and CeO2–Sm2O3 systems have been established under slow-cooled conditions from 1400 °C. The two-phase relations differ as the CeO2–Eu2O3 system showed only two monophasic phase fields, namely F-type cubic and C-type cubic, whereas CeO2–Sm2O3 system showed three phase fields namely F-type cubic, C-type cubic and a biphasic field comprising of C-type cubic and monoclinic phase. An interesting observation of this investigation is the stabilization of C-type rare-earth oxide after Ce4+ substitution, which is attributed to decrease in average cationic size on Ce4+ substitution at RE3+ site. The lattice thermal expansion behavior of F-type solid solution and C-type solid solution in CeO2–Eu2O3 system was investigated by high-temperature XRD. 相似文献
5.
Sintered ZnSxSe1−x films have been prepared in the entire composition range from ZnSe to ZnS by using the screen printing method. To deposit good quality films, optimum conditions have been determined. Wide band gap ternary films have wide applications in solar cells. The band gap of these films are determined by reflection spectra in the wavelength range of 325–600 nm using the Tauc relation. These films have a direct band gap, which varies from 3.50 eV for ZnS to 2.66 eV for ZnSe films. The wurtzite structure of ZnSSe films was confirmed by X-ray diffraction analysis of these films. 相似文献
6.
B-doped a-Si1−xCx:H films for a window layer of Si thin film solar cells have been prepared by the Cat-CVD method. It is found that C is effectively incorporated into the films by using C2H2 as a C source gas, where an only little C incorporation is observed from CH4 and C2H6 under similar deposition conditions. Using a-Si1−xCx:H films grown from C2H2, heterojunction p–i–n solar cells have been prepared by the Cat-CVD method. The cell structure is (SnO2 Asahi-U)/ZnO/a-Si1−xCx:H(p)/a-Si:H(i)/μc-Si:H(n)/Al. The obtained conversion efficiency was 5.4%. 相似文献
7.
An electrode/electrolyte interface has been formed between an n-type CdSe1−xTex (0≤x≤1) alloyed/mixed type semiconductor and a sulphide/polysulphide redox electrolyte. It has been investigated through the current–voltage, capacitance–voltage and spectrally selective properties. The dependence of the dark current through the junction and the junction capacitance on the voltage across the junction have been examined and analysed. It appeared that the current transport mechanism across the junction is strongly influenced by the recombination mechanism at the interface and series resistance effects. Upon illumination of the interface with a light of 20 mW cm−2, an open circuit voltage of the order of 0.35 V and a short circuit current of 212 μA cm−2 have been developed (for x=0.2), yielding an efficiency of energy conversion equal to 0.2% and a form factor of 45%. The action spectra in the 450–1000 nm wavelength range showed presence of the interface states at the electrode/electrolyte interface. The magnitudes of the barrier heights at the interfaces were also determined. It has been seen that a significant improvement in the electrochemical performance of a cell is noticed for the electrode composition with x=0.2. 相似文献
8.
The E1 and E1+Δ1 energy bands of metal–organic chemical vapor deposition grown AlxGa1−xAs, with x in the range 0–0.55, have been determined using photoreflectance technique. The aluminum composition for each sample was determined using the energy of the room-temperature photoluminescence compensated peak value and a suitable fundamental band gap formula. The positions of the E1 and E1+Δ1 peaks were determined from curve-fitting an appropriate theoretical model to our experimental data by a modified downhill simplex method. Using the results, we propose new E1 and E1+Δ1 cubic expressions as functions of the aluminum composition, x, and compare them with the available reported expressions. 相似文献
9.
Nanocrystalline Nd2(Zr1 − xSnx)2O7 series solid solutions were prepared by a convenient salt-assisted combustion process using glycine as fuel. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The results showed the Zr ion can be partially replaced by Sn ion. The partial substituted products were still single-phase solid solutions and the crystal form remained unchanged. TEM images reveal that the products are composed of well-dispersed square-shaped nanocrystals. The method provides a convenient and low-cost route for the synthesis of nanostructures of oxide materials. 相似文献
10.
J. Olejní?ek C.A. KamlerS.A. Darveau C.L. ExstromL.E. Slaymaker A.R. VandeventerN.J. Ianno R.J. Soukup 《Thin solid films》2011,519(16):5329-5334
CuIn1 − xAlxSe2 (CIAS) thin films (x = 0.06, 0.18, 0.39, 0.64, 0.80 and 1) with thicknesses of approximately 1 μm were formed by the selenization of sputtered Cu―In―Al precursors and studied via X-ray diffraction, inductively coupled plasma mass spectrometry and micro-Raman spectroscopy at room temperature. Precursor films selenized at 300, 350, 400, 450, 500 and 550 °C were examined via Raman spectroscopy in the range 50-500 cm− 1 with resolution of 0.3 cm− 1. Sequential formation of InxSey, Cu2 − xSe, CuInSe2 (CIS) and CIAS phases was observed as the selenization temperature was increased. Conversion of CIS to CIAS was initiated at 500 °C. For all CuIn1 − xAlxSe2 products, the A1 phonon frequency varied nonlinearly with respect to the aluminum composition parameter x in the range 172 cm− 1 to 186 cm− 1. 相似文献
11.
The pseudopotential method within the virtual crystal approximation combined with the Harrison bond-orbital model were used to determine all three elastic constants, and hence Poisson's ratio of GaxIn1−xSb semiconductor alloys. Our results for parent compounds are compared to experiment and other theoretical calculations and showed generally good agreement. The effect of compositional disorder on the studied quantities has been examined. We found an important bowing in all elastic constants and bulk modulus versus Ga content. The Poisson ratio was found to be independent of alloy composition x. 相似文献
12.
Nous avons obtenu par épitaxie à partir d'une phase vapeur des couches minces monocristallines de ZnSexSe1−x (0 < x < 1) sur un substrat de fluorine (CaF2) d'épaisseur comprise entre 5 et 30 microm. La méthode utilisée est le transport en tube ouvert, à partir de deux sources (ZnSe et ZnS en poudre), sous flux d'hydrogène. Les vitesses de croissance sont fonction de la température de substrat. L'étude en luminescence montre que ces couches d'orientation (111) sont de bonne qualité. 相似文献
13.
In this study, we report a systematic investigation of the metastable morphologies of Si1−xGex layers obtained by the interplay of kinetics and thermodynamics during growth on Si(001). We show that three main growth regimes can be distinguished as a function of the misfit and of the deposited thickness. They correspond to three equilibrium steady state morphologies that consist of (105)-facetted hut islands, huts and domes in co-existence, and a bimodal size distribution of domes, respectively. The shape transitions between these states are attributed to different levels of relaxation. 相似文献
14.
R.V. Mangalaraja S. Thomas Lee K.V.S. Ramam S. Ananthakumar P. Manohar 《Materials Science and Engineering: A》2008,480(1-2):266-270
The mechanical properties like hardness, Hv and compressive strength, σ of Ni1−xZnxFe2O4 (x = 0.2, 0.3, 0.4 and 0.5) prepared by the non-conventional flash combustion and citrate-gel decomposition techniques are studied and reported. It is observed that there is an increase in hardness with zinc content as well as sintering temperature. The hardness in the order of 2.0–3.63 GPa and compressive strength in the order of 150–240 MPa are obtained for Ni–Zn ferrites prepared by these non-conventional techniques. The influence of density, porosity and microstructure on hardness and compressive strength of Ni–Zn ferrites with respect to sintering temperature was studied. 相似文献
15.
A series of CuCr1 − xNixO2 (0 ≤ x ≤ 0.06) polycrystalline samples was prepared. The electrical conductivity was measured in the temperature range of 160–300 K. It was found that the electrical conductivity (σ) increases rapidly with the doping of Ni2+ ions. At room temperature, the σ is 0.047 S cm− 1 for the sample with x = 0.06, which is two orders of magnitude larger than that of the CuCrO2 sample (9.49E− 4 S cm− 1). The Seebeck coefficients are positive for all samples, which indicate p-type conducting of the samples. The experimental results imply that it is possible to get higher electrical conductivity p-type transparent conducting oxides (TCO) from CuMO2 by doping with divalent ions. 相似文献
16.
Ti1−xVxO2 solid solution film photoelectrodes were prepared by the dip-coating sol–gel method. X-ray diffraction and X-ray photoelectron spectroscopy were employed to ensure the formation of the solid solution and their composition. Obvious photoresponses were observed in the visible region for the solid solution film electrodes with x0.05 and the red shift of the photoresponse was enhanced with increasing x. Moreover, the solid solution film electrodes were found to be photoelectrochemically stable. However, the onset potential of photocurrent shifted positively with increasing x. Band model of the solid solution was suggested to explain the effects of the vanadium incorporation on the photoelectrochemical properties. 相似文献
17.
Oxygen non-stoichiometry, electrical conductivity and thermal expansion of La2−xSrxNiO4−δ phases with high levels of strontium-substitution (1 ≤ x ≤ 1.4) have been investigated in air and oxygen atmosphere in the temperature range 20–1050 °C. These phases retain the K2NiF4-type structure of La2NiO4 (tetragonal, space group I4/mmm). The oxygen vacancy fraction was determined independently from thermogravimetric and neutron diffraction experiments, and is found to increase considerably on heating. The electrical resistivity, thermal expansion and cell parameters with temperature show peculiar variations with temperature, and differ notably from La2NiO4±δ in this respect. These variations are tentatively correlated with the evolution of nickel oxidation state, which crosses from a Ni3+/Ni4+ to a Ni2+/Ni3+ equilibrium on heating. 相似文献
18.
A series of YBa2Cu3−x oxides was synthesized. The results show a cubic system with a simple perovskite structure for x < 0.2 and a face-centered doubled perovskite cell for x > 0.2. There was no indication of the existence of the superconducting 1-2-3 phase for x > 0.2. Solid solution of tungsten was exhibited over the composition region 0.2 < x as well as in the simple perovskite composition range. Analyses of a sample of nominal composition YBa2Cu2W oxide indicates a non-superconducting perovskite with
. 相似文献
19.
Measurements of optical constants (absorption coefficient, refractive index, extinction coefficient, real and imaginary part of the dielectric constant) have been made on a-(Se70Te30)100−x (Se98Bi2)x thin films (where x=0, 5, 10, 15 and 20) of thickness 2000 Å in the wavelength range 450–1000 nm. It is found that the optical bandgap decreases with the increase of Se98Bi2 concentration in the a-(Se70Te30)100−x(Se98Bi2)x system. The value of refractive index (n) decreases, while the extinction coefficient (k) increases with increasing photon energy. The results are interpreted in terms of concentration of localized states varying effective Fermi level. 相似文献
20.
The dielectric function of bulk CuAl1 − xInxSe2 with composition x varying from x = 0.07 to x = 0.6 were studied over the photon energy region 1.0-6.0 eV at room temperature by spectroscopic ellipsometry. Information on the inter-band optical transitions was obtained from the results of the standard critical point analysis of the obtained dielectric function. With increasing Indium content, all spectral features of the obtained dielectric functions were found to gradually shift towards lower energies. The details of this shift for each critical point retrieved from the obtained dielectric function were disclosed. A compositional dependence of the optical transitions in Γ point of the Brillouin zone was verified to be strong. Such dependence for N and T points turned out to be weak by comparison. The later fact was accounted for a small compositional shift of the conduction band states in N and T points as compared to Γ point. 相似文献