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151.
The quaternary alloy InAs1−x−ySbxPy, lattice-matched to InAs, is a promising material for the production of infrared light sources for the detection of gases
in the 2–4 μm region of the spectrum. In this work, thermodynamic phase equilibrium calculations have been carried out to
determine the compositions required for liquid phase epitaxial growth and the extent of the miscibility gap in the solid material.
For high band gap materials, the desired growth temperature is found to be intermediate between a low temperature required
to grow P-rich solids and higher temperatures required to avoidspinodal decomposition. Conventional LPE growth at an intermediate temperature of 583°C is found to produce good material with high
luminescence efficiency and excellent optical characteristics. Problems with phosphorus loss from the melt are also discussed
and lower growth temperatures are found to considerably reduce this problem. Growth in the metastable region between the binodal
and spinodal lines has been achieved with the production of phosphorus-rich solids with concentrations up to y = 0.445. 相似文献
152.
在制作付里叶计算全息过程中,加入适当的二次位相因子,使此种全息图在相干光照明下就可预定的位置上只再现一个像,省略了过去丙现此种计算全息图必要的付里叶透镜,并且使两个互为共轭像分离,从而拓宽了此种计算全息的应用领域,实验结果与理论分析相符。 相似文献
153.
相转移法制备高纯超细TiO2技术研究 总被引:9,自引:0,他引:9
报道了用相转移法制备高纯超细TiO2的新技术;探讨了Ti(Ⅳ)从有机相转移到水相发生水解反应的机理 ;通过TG-DTA分析以及XRD物相分析对水解产物的组成、热分解机理,晶型转变规律进行了研究,建立了水解产物焙烧的最佳温度。 相似文献
154.
The growth of nominally undoped GaSb layers by atmospheric pressure metalorganic vapor phase epitaxy on GaSb and GaAs substrates
is studied. Trimethylgallium and trimethylantimony are used as precursors for the growth at 600°C in a horizontal reactor.
The effect of carrier gas flow, V/III-ratio, and trimethylgallium partial pressure on surface morphology, electrical properties
and photoluminescence is investigated. The optimum values for the growth parameters are established. The carrier gas flow
is shown to have a significant effect on the surface morphology. The optimum growth rate is found to be 3–8 μm/ h, which is
higher than previously reported. The 2.5 μm thick GaSb layers on GaAs are p-type, having at optimized growth conditions room-temperature
hole mobility and hole concentration of 800 cm2 V−1 s−1 and 3·1016 cm-3, respectively. The homoepitaxial GaSb layer grown with the same parameters has mirror-like surface and the photoluminescence
spectrum is dominated by strong excitonic lines. 相似文献
155.
156.
Epitaxial CdTe layers were grown using organometallic vapor phase epitaxy on Si substrates with a Ge buffer layer. Ge layer
was grown in the same reactor using germane gas and the reaction of germane gas with the native Si surface is studied in detail
at low temperature. It is shown that germane gas can be used to “clean” the Si surface oxide prior to CdTe growth by first
reducing the thin native oxide that may be present on Si. When Ge layer was grown on Si using germane gas, an induction period
was observed before the continuous layer of Ge growth starts. This induction period is a function of the thickness of the
native oxide present on Si and possible reasons for this behavior are outlined. Secondary ion mass spectrometry (SIMS) data
show negligible outdiffusion and cross contamination of Ge in CdTe. 相似文献
157.
J. Shin Y. Hsu T. C. Hsu G. B. Stringfellow R. W. Gedridge 《Journal of Electronic Materials》1995,24(11):1563-1569
GalnSb alloys as well as the constituent binaries InSb and GaSb have been grown by organometallic vapor phase epitaxy using
the new antimony precursor trisdimethylaminoantimony (TDMASb) combined with conventional group III precursors trimethylindium
(TMIn) and trimethylgallium (TMGa). InSb layers were grown at temperatures between 275 and 425°C. The low values of V/III
ratio required to obtain good morphologies at the lowest temperatures indicate that the pyrolysis temperature is low for TDMASb.
In fact, at the lowest temperatures, the InSb growth efficiency is higher than for other antimony precursors, indicating the
TDMASb pyrolysis products assist with TMIn pyrolysis. A similar, but less pronounced trend is observed for GaSb growth at
temperatures of less than 500°C. No excess carbon contamination is observed for either the InSb or GaSb layers. Ga1-xInxSb layers with excellent morphologies with values of x between 0 and 0.5 were grown on GaSb substrates without the use of
graded layers. The growth temperature was 525°C and the values of V/III ratio, optimized for each value of x, ranged between
1.25 and 1.38. Strong photoluminescence (PL) was observed for values of x of less than 0.3, with values of halfwidth ranging
from 13 to 16 meV, somewhat smaller than previous reports for layers grown using conventional precursors without the use of
graded layers at the interface. The PL intensity was observed to decrease significantly for higher values of x. The PL peak
energies were found to track the band gap energy; thus, the luminescence is due to band edge processes. The layers were all
p-type with carrier concentrations of approximately 1017 cm3. Transmission electron diffraction studies indicate that the Ga0.5In0.5 Sb layers are ordered. Two variants of the Cu-Pt structure are observed with nearly the same diffracted intensities. This
is the first report of ordering in GalnSb alloys. 相似文献
158.
159.
The hydrodynamic characteristics and mass transfers of halide quaternary salts between two immiscible phases in a stirred membrane permeation cell were investigated. The concentration of quaternary salt, temperature, solvent and the four kinds of halide quaternary salts were evaluated to achieve the extractive optimum condition. The diffusivity, overall mass‐transfer coefficients and individual mass‐transfer coefficients were determined and correlated in terms of the conventional Sh‐Re‐Sc relationship. The transfer time of quaternary salts across the membrane and the thickness of the hydrodynamic diffusion boundary layer were determined as well, so as to characterize the extractive phenomenon of quaternary salts between the two phases that is useful in phase‐transfer catalysis. 相似文献
160.
The problem of the non-causal inversion of linear multivariable discrete-time systems is analyzed in the geometric approach framework and is solved through the computation of convolution profiles which guarantee perfect tracking under the assumption of infinite-length preaction and postaction time intervals. It is shown how the shape of the convolution profiles is related to both the relative degree and the invariant zeros of the plant. A computational setting for the convolution profiles is derived by means of the standard geometric approach tools. Feasibility constraints are also taken into account. A possible implementation scheme, based on a finite impulse response system acting on a stabilized control loop, is provided. 相似文献