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Optical Study (optical + study)

Distribution by Scientific Domains

Physics and Astronomy	80%

Selected Abstracts

Effect of different metal ions on structural, thermal, spectroscopic and optical properties of ATCC and ATMC single crystals

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2007
R. Perumal
Abstract A novel metal-organic coordination complex nonlinear optical crystals, tri-allylthiourea cadmium chloride [(CdCl2(AT)3] and tri-allylthiourea mercury chloride [(HgCl2(AT)3] abbreviated as ATCC, ATMC (AT is Allylthiourea i.e.,CH2=CHCH2NHCSNH2) has been synthesized and grown as single crystals. It was synthesized in deionised water and further recrystallized to improve its purity. Single crystals of the allylthiourea co-ordination complex nonlinear optical crystals tri allylthiourea cadmium chloride (ATCC) with dimensions of 14x14x10 mm3 and tri allylthiourea mercury chloride (ATMC) with dimensions of 15x15x12 mm3 were grown successfully from aqueous solution by solvent evaporation as well as by temperature lowering method. It exhibits powder SHG efficiencies higher than that of a well known organic NLO crystal Urea. The solubility of the as grown crystals was estimated from the aqueous solution and the effect of different metal ions on the grown crystals, structural, thermal, spectral and optical properties were analyzed. XRD studies the reveals the same structure of both materials. Influence of the different central metal (Cd and Hg) atoms, changing the thermal properties of the materials when NLO complexes formed with the common ligand allylthiourea. The metal co-ordination was confirmed form the spectroscopic analysis. From the UV transmittance studies, red shift was from the transparency cut-off wavelengths. The value is 285nm for ATCC is and is 335nm ATMC, Non-linear an optical study confirms the suitabilities of the as grown crystals for the non linear optical applications. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Morphological, structural and optical study of quasi-1D SnO2 nanowires and nanobelts

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10-11 2005
D. Calestani
Abstract 0.1,0.3 mm thick entanglements of quasi-one-dimensional semiconducting Tin dioxide nanocrystals, in form of nanowires and nanobelts, are successfully grown by low cost Chemical Vapour Deposition directly on large area (100 mm2) Al2O3, SiO2 and Si substrates. Their lateral size ranges from 50 to 700 nm and their length can achieve several hundreds of micrometers. Transmission Electron Microscopy reveals either the nanowires and the nanobelts grow in the tetragonal Rutile structure. Diffraction contrast analyses and selected area diffraction investigations show the nanowires are single crystals without defects while the nanobelts sometimes present twins inside. An almost cylindrical shape and an average diameter of about 30,50 nm for the smallest nanowires is reported. X-ray diffraction investigations exclude the presence of spurious phases. A broad band structured in two emissions peaked at about 450 nm and 560 nm is revealed by large area Cathotoluminescence, while single nanocrystal spectroscopy shows that the reduction of the lateral dimension of the nanobelts from 1000 nm to 50 nm blue-shifts the main emission band at 560 nm of about 40 nm (at room temperature). These preliminary results suggest a possible role of oxygen vacancies and of the surface/volume ratio on the origin and the blue shift of Cathodoluminescence spectra. The near band edge emission, typical of bulk tin dioxide (,320 nm), is not found in nanobelts narrower than 1000 nm. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Photo-initiated energy transfer in nanostructured complexes observed by near-field optical microscopy

JOURNAL OF MICROSCOPY, Issue 3 2003
G. A. Wurtz
Summary We report an apertureless near-field optical study on nanostructured objects formed by J-aggregates adsorbed on silver (Ag) nanoparticles. Near-field images reveal that the enhanced near-field from the dressed particle's (DP) resonantly excited plasmon oscillation is efficiently absorbed by the J-aggregates. The sensitivity of the near-field images recorded at the harmonics of the probe vibration frequency suggests that the DP is releasing part of the absorbed energy radiatively upon interaction with the probe. The role of the probe in providing this new radiative relaxation channel is further confirmed as fluorescence from the J-aggregates on the particle is detected on the particle location only. We based the interpretation of our results on the near-field optical response from a bare Ag particle excited at the plasmon resonance as well as on far-field emission and transient absorption experiments. [source]

HRTEM, Raman and optical study of CdS1,xSex nanocrystals embedded in silicate glass

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 13 2004
V. Bellani
Abstract We studied CdS1,xSex nanocrystals embedded in a silicate glass by means of complementary techniques like high resolution transmission electron microscopy (HRTEM), micro-Raman spectroscopy and optical transmission and reflectivity. Transmission Electron Microscopy gives complete information on crystallization and size distribution of the nanocrystals wile Raman scattering is particularly useful in the determination of the composition of the nanocrystals for low-concentration or small-crystallite size composite. Having the size distribution and composition of the nanocrystals we have explained the transmission spectra of the studied samples. Optical transmission spectra evidence the quantization of the electronic states of the nanoparticles system with a size distribution described by a Gaussian function. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Anisotropy dependent magnetization relaxation in (Cd,Mn)Te quantum wells

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2006
M. Goryca
Abstract An optical study of magnetization relaxation is presented for p-doped quantum wells with magnetic ions. The magnetic anisotropy of the system is controlled by the heavy-light hole splitting, tuned by uniaxial strain. We show that a suppression of the magnetic anisotropy results in an enhancement of the observed relaxation rate by a factor of at least 20. This is explained by the fact that the decrease of the anisotropy results in the lowering of the energy barrier for the domain magnetization flip process. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]