Spectroscopic Ellipsometry of Porphyrin Adsorbed in Porous Silicon

Aqueous solution of meso-tetra(4-sulfonatophenyl)porphine was deposited on electrochemically etched n-Si wafers. The morphology of the hybrid systems was investigated by scanning electron microscope and atomic force microscope techniques. The optical response of the hybrid systems was studied by spectroscopic ellipsometry in the range of 1-5 eV. Particular features in adsorption process were revealed for meso-tetra(4-sulfonatophenyl)porphine deposited on variously chemically treated Si substrates. It was found that porphyrin J-aggregates can be intercalated into large pores formed in a bulk n-Si as well as into nanopores of luminescent oxide layer

Optical Response of fci-ZnMgHo Quasicrystal

The results of an optical spectroscopy study of the icosahedral fci-ZnMgHo quasicrystal are presented. The dielectric function of the quasicrystal was measured by the spectroscopic ellipsometry technique in the spectral range of 0.1-5.0 eV. The analysis of the dielectric function shows that an optical response of fci-ZnMgHo is a superposition of the free-electron Drude-type contribution and that of the interband transitions across the fci-ZnMgHo pseudogap

Superconductivity in two-leg spin ladders

The single crystals with two-leg spin-ladder–type structure were investigated. According to the structural, magnetic, optical and resistivity data obtained, the studied crystals $\rm [A{}_2Cu{}_2O{}_3]{}_5[CuO{}_2]{}_7$ were shown, for the first time, to be high-${ T_{\rm c}}$ superconductors (${ T_{\rm c}}$=80 K) which belong to the class of cuprates with incommensurate-type structure

Photoemission and Optical Spectroscopy of i-ZnMgEr Quasicrystal

The results of photoemission and optical studies of icosahedral single-grain ZnMgEr quasicrystals are presented. Synchrotron radiation photoemission measurements were performed on in situ cleaved samples at 10$\text{}^{-10}$ mbar pressure and low, 140-150 K temperature. The valence band photoemission spectra measured reveal a simple metal-type valence band of icosahedral ZnMgEr with a distinct Fermi edge cut-off and with a sharp pseudogap feature. The photoemission spectra of shallow Mg 2p and Zn 3d core levels indicate a coordination shift of Mg 2p spin-orbit doublet and an oscillating dependence of Zn 3d photoemission line components on the photon energy within the hν=20-160 eV range investigated. The optical response of icosahedral ZnMgEr, a dispersion of the dielectric function, was measured by the spectroscopic ellipsometry technique in the 0.5-5.0 eV spectral range. The optical spectra of the quasicrystal indicate the Drude-type optical response superimposed with a peak of interband optical transitions. The interband optical transitions can be modelled with the pseudogap parameters which agree with those deduced in an analysis of the photoemission valence band spectra

Modification of photonic properties in porphyrin-infiltrated opal crystals

The obtained results have shown that using the designed procedure, opal crystals are efficient in retaining the solvents. This is in agreement with the results [15] obtained on sol–gel derived silica matrices impregnated with zinc-sulfonated porphyrins. The optical spectra of opal crystals infiltrated with FeTPPS underwent significant changes due to overlap of the stop band of opal crystals and absorption bands of FeTPPS. The provided experiments have demonstrated that the composite system of opal crystals infiltrated with FeTPPS can be considered as perspective material for magnetophotonic devices. In addition, the investigated hybrid samples can serve as a good model material for studying the optical effects due to overlapping of absorption bands of different origin in photonic crystalsPuslaidininkių fizikos institutasPuslaidininkių fizikos institutas, [email protected] Didžiojo universitetasŠvietimo akademij

Physical studies of porphyrin-infiltrated opal crystals

Artificial opals made of silica spheres and infiltrated with aqueous solution of iron porphyrin (FeTPPS) possessing the absorption band in a visible spectral range were studied. The structural, optical and magnetic properties of composite structures were investigated. Bulk samples of opal structure were obtained by sedimentation technique from colloidal solution Of SiO2 spheres of diameter 240 and 245 nm. The structure of the samples was examined by atomic force microscopy. The properties of photonic crystals were demonstrated by optical measurements in transmission and reflection modes. The stop band was observed in the region 510-550 nm. In samples annealed at 900 degrees C the width of the stop band increased to similar to 70 nm. Aqueous solutions of FeTPPS of concentration similar to 1.0 mM and various pH-values were used for infiltration. The infiltration has led to a change of photonic characteristics, position of the stop band and dependence on light incidence angle. The absorption bands typical of FeTPPS were observed in the vicinity of the stop band. The photonic properties of infiltrated opal structures were determined to depend on the acidity of aqueous solution, which was used in technological procedure. Magnetic properties of FeTPPS-infiltrated opal samples, which have been studied at 5-300 K in magnetic fields up to 5 T, were discussedPuslaidininkių fizikos institutasVytauto Didžiojo universitetasŠvietimo akademij