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1.
Z.Y. Nuru C.J. Arendse T.F.G. Muller M. Maaza 《Materials Science and Engineering: B》2012,177(14):1194-1199
We report on the microstructure and optical properties of AlxOy–Pt–AlxOy interference-type multilayer films, deposited by electron beam (e-beam) deposition onto corning 1737 glass, silicon (1 1 1) and copper substrates. The structural properties were investigated by Rutherford backscattering spectrometry, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The optical properties were extracted from specular reflection/transmission, diffuse reflectance and emissometer measurements. The stratification of the coatings consists of a semi-transparent middle Pt layer sandwiched between two layers of AlxOy. The top and bottom AlxOy layers were non-stoichiometric with no crystalline phases present. The Pt layer is in the fcc crystalline phase with a broad size distribution and spheroidal shape in and between the rims of AlxOy. The surface roughness of the stack was found to be comparable to the inter-particle distance. The optical calculations confirm a high solar absorptance of ∼0.94 and a low thermal emittance of ∼0.06 for the multilayer stack, which is attributed not only to the optimized nature of the multilayer interference stacks, but also to the specific surface morphology and texture of the coatings. These optical characteristics validate the spectral selectivity of the AlxOy–Pt–AlxOy interference-type multilayer stack for use in high temperature solar-thermal applications. 相似文献
2.
Spectrally selective AlxOy/Pt/AlxOy multilayer absorber coatings were deposited onto corning 1737 glass, Si (111) and copper substrates using electron beam (e-beam) vacuum evaporator at room temperature. The employment of ellipsometric measurements and optical simulation was proposed as an effective method to optimize and deposit multilayer solar absorber coatings. The optical constants (n and k) measured using spectroscopic ellipsometry, showed that both AlxOy layers, which used in the coatings, were dielectric in nature and the Pt layer was semi-transparent. The optimized multilayer coatings exhibited high solar absorptance α ∼ 0.94 ± 0.01 and low thermal emittance ? ∼ 0.06 ± 0.01 at 82 °C. The Rutherford backscattering spectroscopy (RBS) data of AlxOy/Pt/AlxOy multilayer absorber indicated the AlxOy layers present in the coating were nearly stoichiometry. The scanning electron microscope analysis (SEM) result indicated that the average diameter and inter-particles distance of Pt grains were statistically about 146 ± 0.17 nm and 6-10 ± 0.2 nm respectively. 相似文献
3.
4.
Integration of NiSix based fully silicided metal gates with HfO2 high-k gate dielectrics offers promise for further scaling of complementary metal-oxide- semiconductor devices. A combination of high resolution transmission electron microscopy and small probe electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis has been applied to study interfacial reactions in the undoped gate stack. NiSi was found to be polycrystalline with the grain size decreasing from top to bottom of NiSix film. Ni content varies near the NiSi/HfOx interface whereby both Ni-rich and monosilicide phases were observed. Spatially non-uniform distribution of oxygen along NiSix/HfO2 interface was observed by dark field Scanning Transmission Electron Microscopy and EELS. Interfacial roughness of NiSix/HfOx was found higher than that of poly-Si/HfO2, likely due to compositional non-uniformity of NiSix. No intermixing between Hf, Ni and Si beyond interfacial roughness was observed. 相似文献
5.
In our previous works, we have shown that most existing ceramic superconductors can be considered to be built of superconductor-semiconductor composite and we have estimated the change in phonon spectrum of the intrinsic superconductor unit if a semiconductor unit is attached to it. Moreover, the proximity effect under the size quantization condition has been examined in the superconductor-semiconductor composite. Each of the stated effects by itself could causeT
c
enhancement in general as more semiconductor blocks are added to the system. We extend our study in this paper to analyze the combined actions of phonon spectral change and proximity effect without size quantization condition onT
c
variation in members of the Tl1 series of high-T
c
superconductors. Our results indicate that an optimumT
c
is obtained if the stated effects are included in the idealized unit cells of the superconductors made up of a superconductor-semiconductor array. 相似文献
6.
K. Racka I. Kuryliszyn M. Arciszewska W. Dobrowolski J.-M. Broto O. Portugall H. Rakoto B. Raquet V. Dugaev E. I. Slynko V. E. Slynko 《Journal of Superconductivity》2003,16(2):289-291
The Anomalous Hall Effect (AHE) was investigated in IV–VI ferromagnetic semimagnetic semiconductors of Sn1–x
Mn
x
Te codoped with either Eu or Er. The analysis of experimental data is as follows. Hall resistivity and magnetization showed that AHE coefficient R
s
depends on temperature and its value decreases with thetemperature increase. We observe that above ferromagnet–paramagnet transition temperature R
s
changes sign. We discuss the possible physical mechanisms responsible for observed temperature dependence of R
s
, particularly change of the sign. 相似文献
7.
A high-pressure technique was adopted to obtain perovskite-type . A new perovskite was characterized to have a cubic symmetry with ; Li and Nb ions in the B-site of perovskite lattice may be in a random arrangement. 相似文献
8.
The preparation conditions of the high TC ceramic superconductor Ba(Pb,Bi)O3 is correlated with the superconducting transition. Transition onsets of all materials are similar, but transition widths and transition completeness is strongly dependent on firing temperature. Only materials prepared over a narrow temperature range, resulting in a nearly ideal weight loss, have a complete and narrow transition. 相似文献
9.
S. Nomura J. Kuwata S.J. Jang L.E. Cross R.E. Newnham 《Materials Research Bulletin》1979,14(6):769-774
The electrostriction in crystals has been investigated using a strain gauge method. In the ferroelectric phase below 140 C, the strain vs the electric field shows a hysteresis, which is ascribed to the effect of ferroelectric domains. A quadratic relation holds between the strain x and the electric polarization P as x = QP2 above about 170 C in the paraelectric phase. Values of the electrostrictive Q coefficients are determined from the measurements near 190 C, as Q11 = 1.6·10?2m4/C2, Q12 = ?0.86·10?2m4/C2, and Q44 = 0.85·10?2m4/C2. 相似文献
10.
The monoclinic-to-tetragonal structure transition of oxides V1?xMox02 with has been studied by means of DTA, X-ray diffraction, magnetic susceptibility (powder samples) and electrical conductivity (single crystals) measurements within the temperature region 80 K to 400 K. A linear decrease of the transition temperature of 11 K per atom % Mo was observed. The magnetic susceptibility of the low temperature phase was found to be temperature independent paramagnetic for all preparations. Electrical conductivity measurements on the same phase showed crystals with to be semiconducting, while a metallic behavior was observed in the region . 相似文献
11.
A. Rogalski 《Thin solid films》1980,67(1):179-186
heterojunctions with a long wavelength spectral cutoff (λc ≈ 6 μm) were prepared using the double-channel hot wall technique. The electrical and photoelectrical properties of the heterojunctions at 77, 197 and 300 K were investigated. Detectors with RoA equal to 170 Ω cm2 and a quantum efficiency of 25–40% were obtained. Reasons for the shift of the long wavelength spectral cutoff of the heterojunctions towards shorter wavelengths are given. 相似文献
12.
N. M?ri M. Takai A. Tomioka S. Ogawa Y. Ueda H. Takahashi S. Katano 《Journal of Superconductivity》1994,7(5):819-821
The superconducting transition temperature,T
c
, of La2–x
Ba
x
CuO4 has been measured under high pressure up to 8 GPa.T
c
is found to change drastically at the pressure where the structural phase transition takes place. This finding clearly indicates that there exists an intimate relation between the crystal structure and superconductivity. 相似文献
13.
SixCyHz films have been prepared at 200°C by reactive plasma deposition from SiH4 and CH4 diluted in helium in a tubular reactor. These films have a ratio s (equal to ranging from 0.2 to 0.8, a refractive index ranging from 1.96 to 2.6 and an optical energy band gap in the range 2.7-2.2 eV. The total quantity of hydrogen in the film is 40% when s=0.5. Infrared analysis shows that these films have large fractions of homonuclear bonds and that this material is best described as a polymer. Mass spectrometric measurements of the gaseous products formed in the SiH4-CH4-He plasma have been performed and the results are related to the composition of the deposited layers. 相似文献
14.
We have studied the influence of surface fields H/sub p/ (generated by either direct or alternating core current) on soft magnetic properties of amorphous and nanocrystalline Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 15.5/B/sub 7/ ribbon. While in an amorphous ribbon the coercive field H/sub c/ decreases with H/sub p/, in the same optimally annealed ribbon (H/sub c/=1.3 A/m, M/sub m//spl ap/M/sub s/) H/sub c/ increases with H/sub p/ for all the explored types of H/sub p/ (static and dynamic with different phases with respect to that of the magnetizing field H). The unexpected increase of H/sub c/ in nanocrystalline ribbon is associated with the influence of H/sub p/ on the surface and main (inner) domain structure. Here, we develop a model that takes into account this influence and explains the experimental results. 相似文献
15.
16.
A new method for obtaining epitaxial CdxHg1?xTe films is presented. The films were prepared by means of a technique in which HgTe was deposited under isothermal conditions onto vacuum-evaporated CdTe films. The structural, optical, electrical and photoelectric properties of the films obtained were investigated.Investigations of the structure showed that films prepared on crystalline substrates (mica, sapphire) are epitaxial while films on amorphous substrates are polycrystalline or textured with large grains. It was found that epitaxial growth on silicon coated with a thin oxide film is possible. Optical investigations showed very good lateral homogeneity of the chemical composition . The deviation Δx from the assumed composition did not exceed 0.003. The results of measurements of the electrical properties showed that the method used permitted us to obtain p- and n-type layers with high or low (n<3x1020m-3 for x=0.2) carrier concentration. The charge carrier mobilities in the epitaxial layers were as high as 3.8 m2 V-1s-1 for x=0.1 at 300 K and exceeded 12 m2 V-1s-1 for x =0.2 at 77 K. The carrier lifetime τ in the best films reached 10-6s(for x=0.26 at 295 K and for x=0.2 at 77 K).The epitaxial CdxHg1?xTe films described here were used as photoconductive detectors in the wavelength range 2–14 μm and as photoelectromagnetic detectors in the range 8–14 μm. 相似文献
17.
Kunets V.P. Pomraenke R. Dobbert J. Kissel H. Muller U. Kostial H. Wiebicke E. Tarasov G.G. Mazur Y.I. Masselink W.T. 《IEEE sensors journal》2005,5(5):883-888
The noise spectrum in micro-Hall devices based on pseudomorphic Al/sub 0.2/Ga/sub 0.8/As/In/sub 0.1/Ga/sub 0.9/As/GaAs modulation-doped heterostructures was measured between 4 Hz and 65 kHz, allowing components due to thermal, 1/f, and generation-recombination to be characterized. Applying deep level noise spectroscopy (DLNS) in the temperature range of 77-300 K to analyze the generation-recombination part of the spectrum, two electron traps contributing to noise density were identified. An emission activation energy of 474 meV was measured for the dominant trap, corresponding to the well-known DX center originating from the AlGaAs barrier. The other deep level, with an emission activation energy of 242 meV, is probably related to defects in the InGaAs layer. The structures under investigation resulted in high-performance micro-Hall devices: a supply-current-related sensitivity up to 725 V/spl middot/A/sup -1//spl middot/T/sup -1/ at 77 K independent of bias current, a signal-to-noise sensitivity of 155 dB/spl middot/T/sup -1/ and a detection limit of 340 pT/spl middot/mm/spl middot/Hz/sup -1/2/ at 77 K were measured. 相似文献
18.
Yuki Furuya Shingo WakaharaMakoto Sugiyama Hidehiko TanakaKentaro Fukuda Noriaki Kawaguchi Yuui YokotaTakayuki Yanagida Akira Yoshikawa 《Optical Materials》2011,34(1):75-78
NaxCa1−2xLux−yNdyF2 single crystals were grown from the melt using the precise atmosphere control type Micro-Pulling-Down (μ-PD) method to investigate their potential as a vacuum-ultraviolet (VUV) scintillators. The grown crystals were single-phase materials with fluorite-type structure (Fm-3m, Z = 4) as confirmed by XRD. The crystals demonstrated 80-90% transmittance above 200 nm wavelength and Nd3+ 5d-4f luminescence (when exited by X-ray) observed around 185 nm. The radioluminescence measurements under 5.5 MeV α-ray excitation (241Am) demonstrated the light yield of 48 [Ph/5.5 MeV-α] and the decay time of 6.4-7.7 ns. 相似文献
19.
A Cd analogue of the Tl and Hgn =3 series with nominal composition CdBa2Ca2Cu3Oy has been synthesized. The samples were superconducting according to magnetic susceptibility measurements. The critical temperature was 103 or 107 K depending on the preparation conditions. The EDX analysis revealed the presence of Cd-1111, Cd-1121, and Cd-2333 as minor phases. The observed diamagnetic effects were attributed to the differentT
c of these phases. 相似文献
20.
In this paper, we describe the optical and electrical gas-sensing properties of In/sub x/O/sub y/N/sub z/ films with an ultrathin gold promoter overlayer. We have fabricated In/sub x/O/sub y/N/sub z/ films with a nanocrystalline porous structure by RF-sputtering in Ar/N/sub 2/ followed by an annealing process. Gold particles with 20-30-nm diameter have been formed on top of the In/sub x/O/sub y/N/sub z/ films by dc sputtering and an annealing process. We have investigated the optical H/sub 2/and NO/sub 2/-sensing properties (change of absorbance) and also the electrical sensing effect (change of electrical resistance) for these two gases. A combined optical/electrical sensor for H/sub 2//NO/sub 2/ is proposed. 相似文献