Manifestation of optical vortices on the surface of solids under irradiation with femtosecond laser pulses

Quasi-periodic microstructures containing dislocations are formed on the surfaces of metals and semiconductors under irradiation with high-power femtosecond laser pulses. Interpretation of microstructures as a result of interference of the incident plane wave and surface waves leads to the logical conclusion about the relationship of dislocations in the interference fringes with optical vortices in surface wave

Light Scattering by Silver Nanoparticles in Colloid Solutions for Improved Photovoltaic Devices

Incorporation of metal nanoparticles (NPs) into photovoltaic cells attracts much attention last years as a promising way for efficiency improvement by light trapping. Precise characterization of light scattering properties of NPs is essential for their successful application. Scattering diagrams and spectra of absorbed light are studied with custom-assembled automated experimental setups. It was found, that 60-240 nm in diameter Ag NPs demonstrate efficient wide-angle light scattering due to excitation of multipole resonances, which manifest themselves as side lobes in the scattering diagrams. Contributions of the multipole modes were also resolved in the absorption spectra of NPs. Direction of light scattering and a red shift of light scattering efficiency maxima, comparing to absorption maxima, studied aiming its application for efficient trapping of long-wavelength radiation in photovoltaic cells

Optical Properties of ZnP2 Nanoparticles in Zeolite

We report that for the first time the nanoparticles of II-V semiconductor (ZnP2) were prepared and studied. ZnP2 nanoparticles were prepared by incorporation into zeolite Na-X matrix. Absorption, diffuse reflection (DR) and photoluminescence (PL) spectra of the ZnP2 nanoclusters incorporated into the supercages of zeolite Na-X were measured at the temperature 77 K. Five bands B1-B5 are observed in both the DR and PL spectra demonstrating the blue shift from the line of free exciton in bulk crystal. We attribute the B1-B5 bands to some stable nanoclusters with size less than the size of zeolite Na-X supercage. We observed Stokes shift of the PL bands from the respective absorption bands. The nonmonotonic character of its dependence on the cluster size can be explained as the result of competition of the Frank-Condon shift and the shift due to electronic relaxation.Comment: Submitted to Microporous and Mesoporous Material

CdSe nanoparticles grown with different chelates

Modified reverse micelles method allowing fabrication of CdSe nanoparticles in toluene solution in series of sizes with average diameter from 1.2 to 3.2 nm and size distribution ∼ 12-30 % is presented. Simple empirical relation between the CdSe nanoparticle diameter and exciton absorption wavelength is proposed, which allows to do prompt and effective monitoring the particles size and size distribution during the synthesis. Optical absorption and photoluminescence measurements as well as EDX demonstrated good quality of obtained nanocrystallites. Besides, study of nanoparticles produced using two complexing agents (SNTA and Trilon B) revealed similar stoichiometric and optical properties. Trilon B is suitable for CdSe nanoparticles growth instead of SNTA. Because of higher stability of the chelate complex of Trilon B and Cd²⁺ ions, it is possible to use higher temperature for growth which allows preparation of large size nanocrystals

Fabrication, Study of Optical Properties and Structure of Most Stable (CdP2)n Nanoclusters

CdP2 nanoclusters were fabricated by incorporation into pores of zeolite Na-X and by laser ablation. Absorption and photoluminescence (PL) spectra of CdP2 nanoclusters in zeolite were measured at the temperatures of 4.2, 77 and 293 K. Both absorption and PL spectra consist of two bands blue shifted with respect to bulk crystal. We performed the calculations aimed to find the most stable clusters in the size region up to size of the zeolite Na-X supercage. The most stable clusters are (CdP2)6 and (CdP2)8 with binding energies of 9.30 eV and 10.10 eV per (CdP2)1 formula unit respectively. Therefore, we attributed two bands observed in absorption and PL spectra to these stable clusters. The Raman spectrum of CdP2 clusters in zeolite was explained to be originated from (CdP2)6 and (CdP2)8 clusters as well. The PL spectrum of CdP2 clusters produced by laser ablation consists of the asymmetric band with low-energy tail that has been attributed to emission of both (CdP2)8 cluster and CdP2 microcrystals.Comment: Accepted for publication in Physica E: Low-dimensional Systems and Nanostructure

Optical Properties and Structure of Most Stable Subnanometer (ZnAs2)n Clusters

ZnAs2 nanoclusters were fabricated by incorporation into pores of zeolite Na-X and by laser ablation. Absorption and photoluminescence spectra of ZnAs2 nanoclusters in zeolite were measured at the temperatures of 4.2, 77 and 293 K. Both absorption and PL spectra consist of two bands which demonstrate the blue shift from the line of free exciton in bulk crystal. We performed the calculations aimed to find the most stable clusters in the size region up to size of the zeolite Na-X supercage. The most stable clusters are (ZnAs2)6 and (ZnAs2)8 with binding energies of 7.181 eV and 8.012 eV per (ZnAs2)1 formula unit respectively. Therefore, we attributed two bands observed in absorption and PL spectra to these stable clusters. The measured Raman spectrum of ZnAs2 clusters in zeolite was explained to be originated from (ZnAs2)6 and (ZnAs2)8 clusters as well. The PL spectrum of ZnAs2 clusters produced by laser ablation consists of a single band which has been attributed to emission of (ZnAs2)8 cluster.Comment: Article accepted for publication in Physica B: Physics of Condensed Matte

Acoustically stimulated phase transition and low temperature optical spectra in PbI₂ crystal

The influence of intensive ultrasonic wave on the crystal structure of PbI₂ was investigated. Acoustically stimulated phase transition have been observed for the first time

Micro- and nanostructuring of metal surfaces with polarized femtosecond laser pulses

Under irradiation of the surface of metals with femtosecond laser pulses, periodic surface micro- and nanostructures have been obtained. The dependence of orientation inherent to formed structures on direction of the electric field related with the incident electromagnetic wave and type of polarization of this wave has been studied. Typically these laser-induced structures are perpendicular to the electric field of incident light and have period shorter than the laser wavelength. The structures oriented in parallel to the polarization vector with a longer period have been also revealed. The dependence of surface structure formation on the initial surface defects in metal has been found

Li₂Zn₂(MoO₄)₃ crystal as a potential detector for ¹⁰⁰Mo 2β-decay search

Properties of Li₂Zn₂(MoO₄)₃ crystals grown by the low-thermal-gradient Czochralski technique have been studied. Chemical composition of the material was tested by ICP-MS mass-spectrometry. Optical properties (refraction, transmittance and reflectivity) have been measured. Luminescence characteristics of crystals under ultraviolet, synchrotron, and X-ray excitation has been studied. Properties and the applicability of Li₂Zn₂(MoO₄)₃ crystals as scintillation and bolometric detectors have been checked for the first time.Досліджено властивості кристалів Li₂Zn₂(MoO₄)₃, вирощених методом Чохральського з низьким температурним градієнтом. Хімічний склад зразків перевірено за допомогою ICP-MS мас-спектрометрії. Виміряно оптичні характеристики (заломлення, прозорість та відбивання). Люмінесцентні характеристики кристалів досліджено при збудженні ультрафіолетовим, синхротронним та рентгенівським випроміненнями. Вперше перевірено можливості використання кристалів Li₂Zn₂(MoO₄)₃ як сцинтиляційних та болометричних детекторів.Изучены свойства кристаллов Li₂Zn₂(MoO₄)₃, выращенных методом Чохральского с низким температурным градиентом. Химический состав проверен при помощи ICP-MS масс-спектрометрии. Измерены оптические свойства (преломление, прозрачность и отражение). Люминесцентные характеристики кристаллов изучены при возбуждении ультрафиолетовым, синхротронным и рентгеновским излучениями. Впервые проверены возможности использования кристаллов Li₂Zn₂(MoO₄)₃ в качестве сцинтилляционных и болометрических детекторов

Li₂Zn₂(MoO₄)₃ crystal as a potential detector for ¹⁰⁰Mo 2β-decay search

Properties of Li₂Zn₂(MoO₄)₃ crystals grown by the low-thermal-gradient Czochralski technique have been studied. Chemical composition of the material was tested by ICP-MS mass-spectrometry. Optical properties (refraction, transmittance and reflectivity) have been measured. Luminescence characteristics of crystals under ultraviolet, synchrotron, and X-ray excitation has been studied. Properties and the applicability of Li₂Zn₂(MoO₄)₃ crystals as scintillation and bolometric detectors have been checked for the first time.Досліджено властивості кристалів Li₂Zn₂(MoO₄)₃, вирощених методом Чохральського з низьким температурним градієнтом. Хімічний склад зразків перевірено за допомогою ICP-MS мас-спектрометрії. Виміряно оптичні характеристики (заломлення, прозорість та відбивання). Люмінесцентні характеристики кристалів досліджено при збудженні ультрафіолетовим, синхротронним та рентгенівським випроміненнями. Вперше перевірено можливості використання кристалів Li₂Zn₂(MoO₄)₃ як сцинтиляційних та болометричних детекторів.Изучены свойства кристаллов Li₂Zn₂(MoO₄)₃, выращенных методом Чохральского с низким температурным градиентом. Химический состав проверен при помощи ICP-MS масс-спектрометрии. Измерены оптические свойства (преломление, прозрачность и отражение). Люминесцентные характеристики кристаллов изучены при возбуждении ультрафиолетовым, синхротронным и рентгеновским излучениями. Впервые проверены возможности использования кристаллов Li₂Zn₂(MoO₄)₃ в качестве сцинтилляционных и болометрических детекторов