Tin sulphide films with thickness of 500~1000 nm were deposited on ITO glass substrates at 30~150°C by a thermal
evaporation technique. The films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM)
and atomic force microscopy (AFM) analysis. The vibrational property of the films was examined by Raman spectra.
The SnS films are polycrystalline with a strong {111} preferred orientation, and they have orthorhombic crystal structure
with a grain size of a few ten nanometers and exhibited near stoichiometric SnS composition. Their lattice parameters are
a=0.4309~0.4313 nm, b=1.1263~1.1273 nm, c=0.3981~0.3990 nm which closely resembles those of bulk SnS at room
temperature. And the substrate temperature has some influence on the composition and structure of the deposited films:
when the substrate temperature increases from 30°C to 150°C, the grains in the films become smaller and the
crystallinity has been improved. sulphide films with thickness of 500~1000 nm were deposited on ITO glass substrates at 30~150°C by a thermal
evaporation technique. The films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM)
and atomic force microscopy (AFM) analysis. The vibrational property of the films was examined by Raman spectra.
The SnS films are polycrystalline with a strong {111} preferred orientation, and they have orthorhombic crystal structure
with a grain size of a few ten nanometers and exhibited near stoichiometric SnS composition. Their lattice parameters are
a=0.4309~0.4313 nm, b=1.1263~1.1273 nm, c=0.39810~.3990 nm which closely resembles those of bulk SnS at room
temperature. And the substrate temperature has some influence on the composition and structure of the deposited films:
when the substrate temperature increases from 30°C to 150°C, the grains in the films become smaller and the
crystallinity has been improved.
In this study, tin precursor layers were deposited on ITO glass substrates by thermal evaporation, and sulphurised in a vacuum furnace at the temperature range between 423-673K, in order to translate the tin layers into compound SnS layers. All the layers synthesized were characterized with X-ray diffractograms, microstructure analysis. It was found that the best SnS films were synthesized for sulphurisation at temperature 573-673K, and they were polycrystalline with a strong {111} preferred orientation, and they had orthorhombic crystal structure with a grain size of a few hundred nanometers and exhibited near stoichiometric SnS composition. The near stoichiometric SnS film was measured to have a p-type electrical conductivity and a resistivity of the order of 102 Ω.cm , and its optical properties were investigated using spectrophotometric measurements of the transmittance and reflectance at normal incidence in the wavelength range 400-2500nm, the films were transparent for a wavelength >1250nm.
In this paper, SnS films were cathodically electrodeposited on ITO glass substrates from aqueous solution containing 5mM SnSO4 and 25mM Na2S2O3 with pH of 2-3. When the deposition potential (E) was varied from -0.60 to -1.1V vs SCE, the corresponding SnS films were characterized with X-ray diffractograms, microstructure and composition analysis. It was found that, the composition ratio Sn/S of the film varied with E, the ratio Sn/S significantly increased and exceeded 1 at E more cathodic than -0.75V vs SCE, and the ratio Sn/S significantly decreased and was less than 1 at E larger than -0.7V vs SCE. The stoichiometric SnS film was synthesized at -0.72~-0.75V vs SCE . The structural and optical properties of the film have been studied. The X-ray diffraction pattern of the film showed that it was polycrystalline and of orthorhombic structure. The estimated optical bandgap energy was 1.31eV.
A modified direct method for subtracting axial scattered light was put forward, that is, when the collimated transmission measured, the axial scattered light was deducted by a small angle scattered light with the same beam size. And μt values of two different samples of human whole blood were measured at laser wavelengths of 488,632.8 and 1341.4nm, respectively. It showed that μt was different for the same blood sample at different wavelength and for different blood sample at the same wavelength.
Monte Carlo method is used to simulate light distribution in human artery of three layers that is irradiated respectively by two different surface photon sources (Guassian beam and flat beam) of 0.06cm radii at wavelength of 633nm. Fluence, diffuse reflectance and diffuse transmission distribution of the tissue are given when the two surface photon sources illuminate the tissue respectively. The influence of the shape of the incident beam on the above parameters, and that of the refractive index n on the diffuse reflectance Rd and absorptance A of the tissue, are discussed. The obtained results are: the diffuse reflectance Rd and fluence Φ are mainly distributed in radial scale of the size of the incident beam, and the influence of the shape of the incidence beam on the radial distribution of Rd and Φ is also in the scale of the size of the incident beam, whereas that of the shape of the incident light beam on the diffuse transmission is little. Rd is linearly decreased with the increasing of n in each layer tissue, but the influence of n in deeper layer tissue on Rd is little; absorptance is linearly increased with the increasing of n in each layer tissue. Therefore, the refractive index is a very important parameter in biotissue.
The relationships between the diffuse reflectance of tissue and its optical parameters (especially the refractive index and the ratio N' of effective scattering coefficient to absorption coefficient) are studied by Monte Carlo method. The limitation in the diffuse reflectance formula fitted by others is found, and a new diffuse reflectance formula which is different for N' in different region is presented. And the diffuse reflectance formulas are obtained for N' = 2 ~ 20 and N' = 40 ~ 100, respectively.
Based on the principle of total internal reflection, a new experimental system , in which the sample is close sandwiched between two prisms, was designed to determine the refractive indices of biotissues and homogeneous medium. Some mammalian tissues have been determined at laser wavelengths ofO.488, 0.6328, 1.0795 and 1.3414?tm, respectively, and their dispersion equations have been obtained. And the absolute error between the n calculated from the dispersion equation and the measured is within 0.002. By utilizing these dispersion equations, the refractive indices of the tissues can be obtained at any wavelength within the waveband of O.488-1.3414?m. The method has great reliability and accuracy, and it can be used for measuring the refractive indices of biotissues and any other medium.
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