Commercial polycrystalline silicon solar cells were textured by the Laser Beam Interference Ablation technique to produce periodical grating in the antireflective and passivation layer. Modeling of periodical hole arrays and refractive index gratings in the antireflective coating on silicon substrate was used to select the fabrication regime and explain alterations in optical properties of the laser treated samples. Visual and elemental analysis of the laser treated areas was performed as well as measurement of photo-electrical characteristics before and after the laser treatment. Two modification regimes were established: ablation and oxidation of the antireflective layer. Changes in surface structure and composition as well as optical and electrical properties of patterned solar cells are discussed.
Composite system of iron porphyrin (FeTPPS) on aminosilanized Si substrates was investigated by studies of surface
morphology and optical response. Aminofunctionalized siloxane films on silicon substrates were produced from
different sol-gel precursors prepared from 3-aminopropyltriethoxysilane (APTES) dissolved in water, ethanol and
acetone. Immersion technique was used for the formation of APTES films. Aqueous solutions of FeTPPS were deposited
on aminosilanized Si substrates. Topographic features of nanostructures in composite FeTPPS/APTES/Si system were
investigated by atomic force microscopy (AFM) technique. High-resolution phase contrast imaging revealed the substructure
of siloxane films on silicon substrates and nanoaggregates of FeTPPS immobilized on aminosilanized Si surface. Spectroscopic ellipsometry measurements were carried out in the region 1-5 eV in order to characterize the siloxane films and composite structures. The analysis of obtained results allowed one to conclude that FeTPPS
molecules were attached to the surface by covalent bonds between the functional group of sulfonic acid SO3- of iron porphyrin and (-NH2H+)-group of APTES.
Magnetic circular dichroism of iron porphyrin aqueous solutions was studied using a photometric ellipsometer with photoelastic
modulator of light polarization in the spectral range 350-750 nm in magnetic fields up to 350 mT. Buffered aqueous solutions of iron
porphyrin with pH-values equal to 1.7, 3.6 and 6.8 and concentration 0.1-1.0 mM were prepared by dissolving Fe(III) meso-tetra(4-
sulfonatophenyl)porphine chloride. The spectra of magnetic circular dichroism were observed in the region of Soret band (390-420
nm) and Q-bands (500-700 nm). The lineshape analysis of magnetic circular dichroism spectra has shown that A-terms were dominant
though a significant overlap masked the fine structure of the Q-bands. The magnetic circular dichroism signal was of order 1x10-2 cm-1/T in a linear approximation with respect to magnetic field. The data indicated that complete lifting of the degeneracy of the states involved in the corresponding optical transitions did not occurred in magnetic fields used. The model of the ground and excited states in iron porphyrin was discussed.
Irena Simkiene, Julija Sabataityte, Jurgis Babonas, Alfonsas Reza, Rita Szymczak, Henryk Szymczak, Marek Baran, Miroslaw Kozlowski, Stanislaw Gierlotka
The iron-containing silica films on Si substrates were prepared by sol-gel technique from precursors composed of
tetraethoxysilane (TEOS) solution in ethanol and FeCl3 water solution. The colloid solutions were deposited by spinning
on cleaned Si substrates and annealed in air, Ar, or H2 atmosphere. The samples were characterized by optical parameters
determined using spectroscopic ellipsometry (1-5 eV) and magnetic properties by measuring the temperature (4-300 K)
and field (up to 50 kOe) dependences of magnetic moment. The physical properties were correlated with sample
structure, which has been examined by atomic force microscope (AFM) and scanning electron microscope (SEM).
In order to characterize TiO2 films in terms of the overall optical response, spectroscopic ellipsometry studies of the system TiO2/Si were carried out. The films were grown by the atomic-layer chemical vapor deposition on Si(111) substrates. Optical measurements were performed by means of a photometric ellipsometer with rotating analyzer. Experimental results have been analyzed using multilayer and pseudodielectric function approximations.
The electronic excitations in complex cuprates are analyzed in the fragment approximation. The fine structure of complex cuprates is considered as the total sum of contributions origination from the electronic excitations in structural and electronic analogues with more simple characteristic units. The analysis was performed on the basis of ellipsometric measurements in the range 0.5-5.0 eV.
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