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61.
The fluorescence spectra of Bacillus spores are measured at excitation wavelengths of 280, 310, 340, 370, and 400 nm. When cluster analysis is used with the principal-component analysis, the Bacillus globigii spores can be distinguished from the other species of Bacillus spores (B. cereus, B. popilliae, and B. thuringiensis). To test how robust the identification process is with the fluorescence spectra, the B. globigii is obtained from three separate preparations in different laboratories. Furthermore the fluorescence is measured before and after washing and redrying the B. globigii spores. Using the cluster analysis of the first two or three principal components of the fluorescence spectra, one is able to distinguish B. globigii spores from the other species, independent of preparing or washing the spores. 相似文献
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The alloy composition of Hg1−xCdxTe should be controlled during growth, so that the desired band gap and the lattice-matched layer may be obtained. In-situ spectroscopic ellipsometry, now commercially available, enables one to acquire spectral data during growth. If one knows
the optical dielectric function as a function of alloy composition and temperature, the technique can be fully used to monitor
and control temperature, the thickness, and the alloy composition. For this purpose, we first obtained temperature dependent
spectral data of Hg1−xCdxTe by spectroscopic ellipsometry (SE). The spectral data of Hg1−xCdxTe with x = 1,0.235, and 0.344 were obtained from room temperature to 800Kin the photon energy range from 1.3 to 6 eV. The spectral
data revealed distinctive critical point structures at E0, E0+Δ0, E1, E1+Δ1, E2(X), and E2(Σ). Critical point energies decreased and linewidths increased monotonically as temperature increased. The model for the
optical dielectric function enabled (i) the critical point parameters to be determined accurately, and (ii) the spectral data
to be expressed as a function of temperature within and outside the experimental range. 相似文献
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65.
Shubhrangshu Mallick Rajni Kiran Siddhartha Ghosh Silviu Velicu Sivalingam Sivananthan 《Journal of Electronic Materials》2007,36(8):993-999
A comparative study of wet etchants for both molecular beam epitaxy (MBE) and liquid phase epitaxy (LPE) grown n- and p-type samples was performed using capacitance–voltage (C–V) characteristics and surface recombination velocity (SRV) extracted
from photoconductive decay (PCD) measurements. Different wet etchants were divided in two categories, (i) where bromine is
a direct reagent in the etching solution and (ii) where bromine is a byproduct after reaction among different reagents. Negative
shift of the flat-band voltages were observed for both n- and p-type samples treated with second category of etchants. A decrease in minority carrier lifetimes and an increase in the surface
recombination velocities were also observed for the n-type samples treated with second category of etchants. 相似文献
66.
M. Daraselia J. W. Garland B. Johs V. Nathan S. Sivananthan 《Journal of Electronic Materials》2001,30(6):637-642
Spectroscopic ellipsometry (SE) has proven to be a very reliable technique for the in-situ monitoring of the substrate temperature
and alloy composition during the HgCdTe epitaxy. In this work, the influence of the variations in the angle of incidence and
the spectral wavelength shift on the measured accuracy of the growth temperature and alloy composition are studied, and a
method for precisely determining these variations independent of the modeling of the SE data has been developed. It is shown
that the stability of the fittings of the optical models for in-situ applications increases and that the couplings between
model parameter decreases upon either eliminating the angle of incidence as an independent model parameter or correcting for
the shifts of the wavelength offset. The variations in the angle of incidence and wavelength shift, which arise in the M88
ellipsometer from reflected beam deflections, were precisely calibrated in two dimensions as a function of alignment parameters,
using a thick thermally grown SiO2/Si sample and were parameterized for our experimental geometry. A new extension of theWVASE software was developed to correct the raw SE data in real time for wavelength shift and the angle of incidence drift. A comparison
of the corrected and uncorrected results of in-situ temperature measurements for HgCdTe and CdZnTe(211) B/Si(211) clearly
demonstrates that the proposed method significantly enhances the accuracy of temperature and composition readings over a broad
range of values in these parameters. 相似文献
67.
Juncheng Liu Jiao Li Guodong Zhang Changxing Li Craig Lennon Siva Sivananthan 《Journal of Electronic Materials》2007,36(8):971-980
The effects of artificial forced cooling on the solid–liquid interface and on solute segregation were investigated by modeling
the vertical Bridgman method for the single-crystal growth of CdZnTe, taking into consideration effects such as increasing
the axial outward heat flux from the crucible bottom, the radial outward heat flux from the crucible wall, and the carbon
film thickness on the crucible inner wall. Axial artificially forced cooling noticeably increases convection and the temperature
gradient in the melt next to the solid–liquid interface, and substantially reduces interface concavity at the initial solidification
stage. Interface concavity increases a little when the solidification proceeds further, however. Axial artificially forced
cooling reduces radial solute segregation of the initial segment of the grown crystal and slightly increases the solute iso-concentration
segment. Radial artificially forced cooling enhances melt convection substantially, affects solid–liquid interface concavity
only slightly, and hardly affects solute segregation in the grown crystal. Doubling the carbon film thickness weakens convection
of the melt in front of the interface, substantially increases interface concavity, and hardly affects solute segregation
in the grown crystal. 相似文献
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