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1.
Porous GaAs layers have been formed by anodic etching of n +-type GaAs (10.0) substrates in a HF:C 2H 5OH:HCl:H 2O 2:H 2O electrolyte. A dramatic impact of etching time on the optical and structural properties of porous GaAs layer is demonstrated. The nano/micro-features of porous GaAs layers are revealed by scanning electron microscopy (SEM) imaging. Two-peak room temperature photoluminescence (PL), “blue-green” and “green-yellow”, is obtained in all prepared porous GaAs samples. Proper adjustment of etching time is found to produce a white color layer, instead of the usual dark gray color of porous GaAs. This is found to cause vast enhancement in the intensity of the visible PL in porous GaAs layer. Chemical composition and structural characterization by means of X-ray photoelectron spectroscopic (XPS), X-ray diffraction (XRD), and micro-Raman spectroscopy, confirm that this layer is characterized with monoclinic β-Ga 2O 3 rich surface. Etching time induced—modification of structural and chemical properties of porous GaAs layer is discussed and correlated to its PL behavior. It is inferred that the “blue-green” PL in porous GaAs can be ascribed to different degrees of quantum confinement in GaAs nanocrystallites, whereas, the “green-yellow” PL is highly influenced by the As 2O 3 and Ga 2O 3, content in the porous GaAs layer. In addition, the reflectance measurements reveal an anti-refection trend of behavior of porous GaAs layers in the spectral range (500–1,100 nm). 相似文献
2.
Zinc oxide (ZnO) thin films were grown at 70 °C by plasma-enhanced atomic layer deposition using H2O and O2 plasmas. Plasma oxidants were used in order to improve the ZnO crystallinity and optoelectronic properties, avoiding high-temperature synthesis. The deposition parameters were optimized to achieve saturation in each reaction step. X-ray photoelectron spectroscopy (XPS) reveals high purity of the obtained ZnO films. X-ray diffraction (XRD) measurements indicate that the grown layers are polycrystalline and that the H2O plasma synthesis leads to better crystallinity than the O2 plasma as inferred from the intensity of the (100) and (002) peaks. The films are with high optical transmission, ~90%, as inferred from UV–visible (UV–Vis) transmittance measurements, and optical band gaps of 3.22 and 3.23 eV for H2O and O2 plasma, respectively. Atomic force microscopy (AFM) indicates that the films are smooth, with an average roughness of ~?0.22 nm. The growth rate was found to be in the range of 1.2–1.4 Å/cycle. The XPS, XRD, UV–Vis, and AFM results prove the possibility to obtain high-quality ZnO films by O2 and H2O plasma processes at 70 °C with chemical, structural, and optical properties promising for flexible electronics. ZnO films were successfully deposited on polyethylene terephthalate substrates using the optimal conditions for H2O plasma process. No damage of the film surface or substrate was observed. 相似文献
3.
The structural, optical and morphological properties of Ga-rich Ga xIn 1?xP layers with various gallium compositions grown on epi-ready semi-insulating (100)-oriented GaAs substrates by using Molecular Beam Epitaxy technique are presented in this study. The Ga xIn 1?xP/GaAs structures ( S1, S2 and S3) have been evaluated by means of high resolution X-ray diffraction, photoluminescence (PL) and atomic force microscopy measurements at room temperature. Experimental forward and reverse bias current–voltage ( I– V) characteristics of structure S3 was investigated at room temperature due to its better characteristics when compared to the other two samples. The main electrical parameters such as ideality factor ( n), barrier height (Φ b ) and series resistance ( R s ) were extracted from forward bias I– V characteristics and Cheung’s function. In addition, Hall measurements were carried out as a function of temperature (30–300 K) and at a magnetic field of 0.4 T were presented for structure S3. 相似文献
4.
Our technique of reactive thermal co-evaporation has been extended to fabricate large films (up to 4 in.) of YBa 2Cu 3O 7 with high quality. A rotating substrate holder is used to separate the deposition and oxidation processes. This allows free access of the metal vapors. As large substrate wafers we use Al 2O 3, Si, and GaAs with buffer layers of CeO 2, YSZ, and MgO, respectively. On all substrates, the uniformity of thickness and composition was better than 2%. Inductively measured T c and j c (77 K) were 87.5±0.2 K and >1×10 6 A/cm 2, respectively, across the full wafer area. This holds also for GaAs substrates due to a new procedure of capping by Si 3N 4. 相似文献
5.
Semiconductive nanometer-sized ZnCr 2O 4 material synthesized by a solution combustion method using inorganic reagents as Zn(NO 3) 3·6H 2O, Cr(NO 3) 3·6H 2O, and glycine as a fuel. This process is a convenient, environment friendly, inexpensive and efficient for the preparation of ZnCr 2O 4 nanomaterial. The synthesized material is characterized by thermo gravimetric differential analysis, X-ray diffraction studied, energy dispersive X-ray microanalysis studies and transmission electron microscopy techniques. The increase in conductivity with increasing temperature could be attributed to negative temperature coefficient of resistance and semiconducting nature of ZnCr 2O 4. 相似文献
6.
The ability of sodium nitrate/urea mixture in the presence of tetrahydrofuran to enhance the purity of uranium produced from crude yellowcake with the subsequent preparation of different forms of highly pure uranium oxides (UO 4·4H 2O, U 3O 8, UO 3) was examined. The methods of X-ray fluorescence, X-ray diffraction, and energy-dispersive X-ray analysis and inductively coupled plasma optical emission spectrometry were used. The highest uranium purity was reached using 1 M NaNO 3 + 1 or 2 M urea. The uranium loss from the crude yellowcake was insignificant. 相似文献
7.
This work reports the production of hydroxyapatite (HA) sub-micron fibers by combining electrospinning and a non-alkoxide sol-gel system, using cheap precursors. Phosphorus pentoxide (P 2O 5) and calcium nitrate tetrahydrate (Ca(NO 3) 2.4H 2O) were used as precursors of phosphorus and calcium, respectively. The fibers were electrospun from a mixture of the gel formed from the system Ca(NO 3) 2.4H 2O/P 2O 5 with polymeric solutions of polyvinylpyrrolidone (PVP) in water and ethanol/water mixtures. The fibers were analyzed for their morphology (Scanning Electron Microscopy, SEM), chemical composition (Fourier Transform Infrared Spectroscopy, FTIR) and structure (X-ray diffraction, XRD). The fibers obtained were composed mainly of type B carbonated HA with traces of β-tricalcium phosphate (β-TCP). SEM analysis revealed that increasing the concentration of water in the solvent system, used in the preparation of electrospinning solutions, led to fibers with smaller diameters and narrower diameter distribution. 相似文献
8.
Lanthanum acetylacetonate La(C 5H 7O 2) 3· xH 2O has been used in the preparation of the precursor solution for the deposition of polycrystalline La 2O 3 thin films on Si(1 1 1) single crystalline substrates. The precursor chemistry of the as-prepared coating solution, precursor powder and precursor single crystal have been investigated by Fourier Transformed Infrared Spectroscopy (FTIR), differential thermal analysis coupled with quadrupole mass spectrometry (TG-DTA-QMS) and X-ray diffraction. The FTIR and X-ray diffraction analyses have revealed the complex nature of the coating solution due to the formation of a lanthanum propionate complex. The La 2O 3 thin films deposited by spin coating on Si(1 1 1) substrate exhibit good morphological and structural properties. The films heat treated at 800 °C crystallize in a hexagonal phase with the lattice parameters a = 3,89 Å and c = 6.33 Å, while at 900 °C the films contain both the hexagonal and cubic La 2O 3 phase. 相似文献
9.
In this work, beta zeolite membranes were prepared on seeded α-Al 2O 3 substrate tubes using zeolite structure-directing agent (ZSDA), instead of directly using organic agent as templates. This ZSDA method consists of two steps: preparation of beta ZSDA and growth of beta zeolite membranes with ZSDA by the secondary hydrothermal synthesis. The molar compositions of the synthesis solution of ZSDA and zeolite membrane are of 1SiO 2/0.012Al 2O 3/0.167(TEA) 2O/0.031Na 2O/9.4H 2O and 1SiO 2/0.03Al 2O 3/0.027(TEA) 2O/0.27Na 2O/25H 2O, respectively. Preparing the membranes only needed a little ZSDA, which was used to substitute for conventional templates in the secondary growth process of the membrane. The membranes were characterized by SEM, XRD and nitrogen permeance. It was found that the prepared membranes are continuous and defect-free. The mechanism of membrane growth with ZSDA was discussed simply. 相似文献
10.
Zinc borate (Zn 2B 6O 11·3H 2O) nanoparticles were successfully prepared by using an emulsion liquid membrane (W/O/W emulsion) to control the size of particles with Na 2B 4O 7·10H 2O, boric acid and ZnSO 4·7H 2O as raw materials. All materials were dispersed with the polyimide (PI) precursor, poly (amic acid). Using a combination of dissolving the poly (amic acid) and mixing fatty acid surfactant-coated zinc borate nanoparticles; we have demonstrated the formation of nanocomposites with uniform nanoparticles dispersion. We report the first deposition of nanocomposite polyimides from solution using spin-coating. The microstructures and morphology of the as-obtained samples were studied by X-ray diffraction (XRD), infrared spectra (IR), scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDX), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). 相似文献
11.
Films of Eu-doped GaN (GaN:Eu) were grown on c-plane of sapphire (c-Al 2O 3), GaAs(1 0 0), Si(1 0 0) and glass substrates by RF magnetron sputtering method. The X-ray diffraction (XRD) measurement of the sputtered film was carried out. For GaN:Eu and undoped GaN, the lattice constants c and a of as-grown films were larger than those of the bulk GaN. After annealing, the lattice constants c and a of the films decreased. 相似文献
12.
Our technique of reactive thermal co-evaporation has been extended to fabricate large films (up to 4 in.) of YBa 2Cu 3O 7 with high quality. A rotating substrate holder is used to separate the deposition and oxidation processes. This allows free access of the metal vapors. As large substrate wafers we use Al 2O 3, Si, and GaAs with buffer layers of CeO 2, YSZ, and MgO, respectively. On all substrates, the uniformity of thickness and composition was better than 2%. Inductively measured T
c
and j
c
(77 K) were 87.5±0.2 K and >1×10 6 A/cm 2, respectively, across the full wafer area. This holds also for GaAs substrates due to a new procedure of capping by Si 3N 4.This work was supported by the German Bundesminister für Forschung und Technologie. 相似文献
13.
Calcium phosphate coatings on Ti6Al4V substrates were elaborated by pulsed electrodeposition with hydrogen peroxide (H 2O 2) into electrolyte. The surface morphology and the chemical composition of the coatings were characterized by scanning electron microscopy (SEM) associated to Energy Dispersive X-ray Spectroscopy (EDXS) for X-ray microanalysis. The obtained results were systematically confirmed at the nanometre scale analysis using scanning transmission electron microscopy (STEM). Moreover, X-ray diffraction (XRD) was performed in order to identify the coatings phases. The results showed that pulsed electrodeposition without H 2O 2 into electrolyte followed by heat treatment favoured coatings made of two phases which are stoichiometric hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP). On the other hand the addition of an optimized H 2O 2 amount into electrolyte led to adherent and uniform coatings mainly made of stoichiometric hydroxyapatite (HAP). 相似文献
14.
NaMg(H 2O) 2[BP 2O 8]·H 2O was prepared by hydrothermal synthesis and was characterized by X-ray powder difraction and IR method. The title compound was synthesized from MgCl 2·6H 2O, NaBO 3·4H 2O, and (NH 4) 2HPO 4 with variable molar ratios using hydrothermal method by heating at 165 °C for 3 days. The X-ray powder diffraction data was indexed in hexagonal system, the unit cell parameters were found to be as a = 9.428, c = 15.82 Å, Z = 4 and the space group is P6 122. It is isostructural with M lM ll(H 2O)[BP 2O 8] type compounds where M l = Na, K; M ll = Mg, Mn, Fe, Co, Ni and Zn. In addition NH 4Mg(H 2O) 2[BP 2O 8]·H 2O was also synthesized the first time in this research. Its unit cell parameters and hkl values were in good agreement with the sodium magnesium compound. The unit cell parameters are a = 9.529, c = 15.736 Å. The indexed X-ray powder diffraction data of both compounds which were not reported in the literature is presented in this work. The IR data of NaMg(H 2O) 2[BP 2O 8]·H 2O is also reported. 相似文献
15.
Crystalline CoO/Co 3O 4 particles with polyhedral morphologies have been successfully synthesized via a versatile spray roasting method. The feed solution was prepared using distilled water or ethanol–water mixture as solvent while CoCl 2·6H 2O as solute, and then sprayed by an inner mixed air-nozzle and roasted in an erective tubular resistance furnace with compressed air as carrier gas. The as-prepared specimens were characterized by X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM) and FT-IR spectroscopy. The results showed that pure crystalline Co 3O 4 particles have been obtained under the condition of H 2O was used as the sole menstruum while CoCl 2·6H 2O was used as the core materials. Meanwhile, the pure well-crystallized CoO particles with octahedron morphology were obtained successfully by dissolving CoCl 2 in ethanol–water mixture solution concentrated CH 3CH 2OH–H 2O (1:1, v/v) as reactants. The possible reaction mechanism of different solvent in the synthesis process was elucidated as well. 相似文献
16.
Hydroxyapatite-containing titania coatings on titanium substrates were formed by micro-arc oxidation (MAO) in electrolyte containing calcium acetate monohydrate (CH 3COO) 2Ca·H 2O) and sodium phosphate monobasic dihydrate (NaH 2PO 4·2H 2O) using a pulse power supply. Scanning electron microscopy (SEM) with Energy dispersive X-ray spectrometer (EDX) and X-ray diffraction (XRD) were employed to characterize the microstructure, elemental composition and phase components of the coatings. The coatings were rough and porous, without apparent interface to the titanium substrates. All the oxidized coatings contained Ca and P as well as Ti and O, and the porous coatings were made up of anatase, rutile and hydroxyapatite. Such MAO films are expected to have significant applications as artificial bone joints and dental implants. 相似文献
17.
The objective of this study is to propose a photocatalysis-assisted chemical mechanical polishing (PCMP) method for atomic smoothing SiC wafer based on the powerful oxidability of UV photo-excited hydroxyl radical on nano-TiO 2 particles. The study identifies five slurries of different photocatalyst, electron capturer, UV light, and pH value by measuring oxidation reduction potential and static oxidation experiment. After PCMP process, a SiC wafer is examined with optical microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy for information on surface finish and quality, material removal and mechanisms. The study demonstrates that photocatalyst, UV light, electron capturer, and acid environment are necessaries for PCMP process. Among the five PCMP slurries, the one with 1?g of TiO 2, 0.3?g of (NaPO 3) 6, 10?ml H 2O 2, 5?g SiO 2 abrasives under UV light irradiation provides the highest material removal rate of 0.95?µm/h and the best surface finish (Ra?=?0.35?nm) and surface quality. It then discusses how UV light irradiation promotes the chemical oxidation of hydroxyl radical with SiC by forming “Si–C–O,” “Si–O,” “C–O,” and “C?O” on SiC surface. The study concludes that the proposed PCMP is effective and clean manufacturing method for SiC wafer without releasing toxic chemicals to environment and human health. 相似文献
18.
Nanoparticles of NiAl 2O 4 were synthesized by heating (500-1000 °C) the dried resin resultant of a mixture in aqueous solution of gelatin, NiCl 2·6H 2O and AlCl 3·6H 2O. The particle size and microstrain were calculated from the line broadening of X-ray powder diffraction peaks through the Rietveld method refinement: these are 3.9-16 nm and − 0.743-0.139%, respectively. The NiAl 2O 4 nanoparticles were characterized by X-ray powder diffraction (XRPD), thermo gravimetric analysis (TG), BET and TEM techniques. 相似文献
19.
Chemical preparation, crystallographic characterization, thermal behavior and IR studies are given for two new cyclotriphosphates SrTlP 3O 9·3H 2O and SrTlP 3O 9. SrTlP 3O 9·3H 2O is orthorhombic, space group Pnma, with the following unit-cell dimensions: a=9.147(7) Å, b=8.180(7) Å, c=15.458(2) Å and Z=4. The total dehydration of SrTlP 3O 9·3H 2O leads between 300 and 650°C to its anhydrous form SrTlP 3O 9. SrTlP 3O 9 is monoclinic, space group P2 1/ m or P2 1, with the following unit-cell dimensions: a=14.544(2) Å, b=8.639(1) Å, c=7.727(1) Å, β=102.05(1)° and Z=4. The thermal behavior has been investigated and interpreted in agreement with IR absorption spectrometry and X-ray diffraction experiments. We calculated the 30 normal frequencies of the P 3O 9 ring with Cs symmetry and proposed the interpretation of the vibrational spectrum of SrTlP 3O 9·3H 2O. The vibrations were assigned and precised to each frequency for different atoms of the ring on the basis of the results of the theoretical isotopic substitutions and in the light of the crystalline structure of the isotypic compounds, SrM IP 3O 9·3H 2O (M I=Rb +, K + and NH 4+), of SrTlP 3O 9·3H 2O. 相似文献
20.
Hydroxyapatite (HAp) coatings were prepared on 316L stainless steel (316LSS) substrates by electrochemical deposition in the solutions containing Ca(NO 3) 2·4H 2O and NH 4H 2PO 4 at different electrolyte concentrations. Along with the effect of precursor concentration, the influence of temperature and H 2O 2 content on the morphology, structure and composition of the coating was thoroughly discussed with the help of X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectra. The in vitro tests in simulated body fluids (SBF) were carried out and then the morphological and structural changes were estimated by SEM and electrochemical techniques (open circuit potential, polarization curves, Nyquist and Bode spectra measurements). Being simple and cost-effective, this method is advantageous for producing HAp implant materials with good properties/characteristics, aiming towards in vivo biomedical applications. 相似文献
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