ABSTRACT Characterization of tumor-to-normal endogenous optical contrast from 3D diffuse optical ... more ABSTRACT Characterization of tumor-to-normal endogenous optical contrast from 3D diffuse optical tomography, neoadjuvant chemotherapy monitoring with additional blood flow information, and 3D fluorescence DOT with exogenous contrast agent injection are presented.
Electronic spectra of porous Si have been investigated in the region $<$4 eV below the Fermi l... more Electronic spectra of porous Si have been investigated in the region $<$4 eV below the Fermi level with specimens subjected to in situ oxygenation and thermal treatments. The significance of DOS to the photoluminescence and its degradation in porous Si is discussed. Fine structure of the photoelectron spectra is found from specimens heated in oxygen at 600 K.
Electronic spectra of porous Si have been investigated in the region &amp;lt;4 eV below the F... more Electronic spectra of porous Si have been investigated in the region &amp;lt;4 eV below the Fermi level with specimens subjected to in-situ oxygenation and thermal treatments. The measurements were made with a UHV photoelectron spectrometer using “soft” energy (hν=8.43 eV) excitation of the photoemission. The significance of the density of occupied states to the photoluminescence and its degradation in porous Si is discussed. Fine structure of the photoelectron spectra is found from specimens heated in oxygen at 600 K.
ABSTRACT Effects of the surface atomic structures on the electron spectrum and luminescent proper... more ABSTRACT Effects of the surface atomic structures on the electron spectrum and luminescent properties of porous silicon (por-Si) were studied by methods of photoluminescence spectroscopy, UV photoelectron spectroscopy, and Fourier-transform IR spectroscopy. An analysis of evolution of the por-Si characteristics in the course of thermal treatment in vacuum revealed a correlation between the photoluminescence spectrum and intensity, on the one hand, and the electron spectrum and surface atomic structure, on the other hand. The thermodesorption of adsorbate from por-Si leads to atomic rearrangements on the sample surface, which is accompanied by changes in the electron structure and, hence, in the luminescent properties of the material.
ABSTRACT The structure of the spectrum of the partial density of filled states of Bi2Sr2CaCu2O8 i... more ABSTRACT The structure of the spectrum of the partial density of filled states of Bi2Sr2CaCu2O8 in the range E b&lt;4 eV, obtained by ultraviolet (hv=8.43 eV) photoelectron spectroscopy was compared with that calculated by the strong coupling method. The results of the calculations agree with the experimental results in the range of binding energies 1&lt;E b &lt;4 eV. Analysis of the evolution of the spectra under thermal and phototreatment in ultrahigh vacuum and in oxygen reveals that oxygen atoms from Cu-O planes possess the highest mobility in the lattice and the surface of the single crystal is formed by Bi-O planes.
ABSTRACT A study has been made of the transformation of photoluminescence (PL) spectra of porous ... more ABSTRACT A study has been made of the transformation of photoluminescence (PL) spectra of porous silicon (PS) induced by its ageing, including the early stages of contact with air. The sample was prepared under conditions that minimized this contact, and spectral measurements were carried out in a high vacuum or in liquid nitrogen. The PS PL spectra obtained under continuous measurement in high vacuum are always dominated by one emission band of PS nanoelements, which shifts toward shorter wavelengths with ageing by 150 nm. At 80 K, the band intensity is considerably higher than at 300 K, and this difference grows with ageing. Exposure of a sample to air for a few tens of seconds is long enough to strongly transform its time-resolved PL spectra, which is evidence of a change in the sample surface. The effect of immersion of PS samples in liquid nitrogen on PL spectra is associated not only with their cooling, but also with the field of adsorbed nitrogen molecules, whose influence becomes weaker with increasing thickness of the oxidized near-surface layer. The variation of the spectral properties and kinetics of the long-wavelength PS PL band with temperature, medium (liquid nitrogen or vacuum), and exposure time suggest that these factors affect carrier migration between silicon nanoelements.
ABSTRACT Characterization of tumor-to-normal endogenous optical contrast from 3D diffuse optical ... more ABSTRACT Characterization of tumor-to-normal endogenous optical contrast from 3D diffuse optical tomography, neoadjuvant chemotherapy monitoring with additional blood flow information, and 3D fluorescence DOT with exogenous contrast agent injection are presented.
Electronic spectra of porous Si have been investigated in the region $<$4 eV below the Fermi l... more Electronic spectra of porous Si have been investigated in the region $<$4 eV below the Fermi level with specimens subjected to in situ oxygenation and thermal treatments. The significance of DOS to the photoluminescence and its degradation in porous Si is discussed. Fine structure of the photoelectron spectra is found from specimens heated in oxygen at 600 K.
Electronic spectra of porous Si have been investigated in the region &amp;lt;4 eV below the F... more Electronic spectra of porous Si have been investigated in the region &amp;lt;4 eV below the Fermi level with specimens subjected to in-situ oxygenation and thermal treatments. The measurements were made with a UHV photoelectron spectrometer using “soft” energy (hν=8.43 eV) excitation of the photoemission. The significance of the density of occupied states to the photoluminescence and its degradation in porous Si is discussed. Fine structure of the photoelectron spectra is found from specimens heated in oxygen at 600 K.
ABSTRACT Effects of the surface atomic structures on the electron spectrum and luminescent proper... more ABSTRACT Effects of the surface atomic structures on the electron spectrum and luminescent properties of porous silicon (por-Si) were studied by methods of photoluminescence spectroscopy, UV photoelectron spectroscopy, and Fourier-transform IR spectroscopy. An analysis of evolution of the por-Si characteristics in the course of thermal treatment in vacuum revealed a correlation between the photoluminescence spectrum and intensity, on the one hand, and the electron spectrum and surface atomic structure, on the other hand. The thermodesorption of adsorbate from por-Si leads to atomic rearrangements on the sample surface, which is accompanied by changes in the electron structure and, hence, in the luminescent properties of the material.
ABSTRACT The structure of the spectrum of the partial density of filled states of Bi2Sr2CaCu2O8 i... more ABSTRACT The structure of the spectrum of the partial density of filled states of Bi2Sr2CaCu2O8 in the range E b&lt;4 eV, obtained by ultraviolet (hv=8.43 eV) photoelectron spectroscopy was compared with that calculated by the strong coupling method. The results of the calculations agree with the experimental results in the range of binding energies 1&lt;E b &lt;4 eV. Analysis of the evolution of the spectra under thermal and phototreatment in ultrahigh vacuum and in oxygen reveals that oxygen atoms from Cu-O planes possess the highest mobility in the lattice and the surface of the single crystal is formed by Bi-O planes.
ABSTRACT A study has been made of the transformation of photoluminescence (PL) spectra of porous ... more ABSTRACT A study has been made of the transformation of photoluminescence (PL) spectra of porous silicon (PS) induced by its ageing, including the early stages of contact with air. The sample was prepared under conditions that minimized this contact, and spectral measurements were carried out in a high vacuum or in liquid nitrogen. The PS PL spectra obtained under continuous measurement in high vacuum are always dominated by one emission band of PS nanoelements, which shifts toward shorter wavelengths with ageing by 150 nm. At 80 K, the band intensity is considerably higher than at 300 K, and this difference grows with ageing. Exposure of a sample to air for a few tens of seconds is long enough to strongly transform its time-resolved PL spectra, which is evidence of a change in the sample surface. The effect of immersion of PS samples in liquid nitrogen on PL spectra is associated not only with their cooling, but also with the field of adsorbed nitrogen molecules, whose influence becomes weaker with increasing thickness of the oxidized near-surface layer. The variation of the spectral properties and kinetics of the long-wavelength PS PL band with temperature, medium (liquid nitrogen or vacuum), and exposure time suggest that these factors affect carrier migration between silicon nanoelements.
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Papers by A. Aprelev