Laser ablation lithography on thermoelectric semiconductor

In this paper, experimental results of the investigation of the periodic structure on thermoelectric semiconductor Cu₂Se are presented. Periodic structures were formed on surfaces of semiconductors due to multi-beam interaction of Q-switched Nd:YAG laser, which was operated in the lowest order of Gaussian mode and pulse duration 7 ns. Surface temperature evolution and transient reflectivity are studied during laser treatment. Creation of Cu islands in the maximal intensity of interference pattern was found.     

Structural properties of the condensate in two-dimensional mesoscopic systems of strongly correlated excitons

A two-dimensional mesoscopic Bose system of dipoles in a 2D trap is considered using computer simulation by the quantum path-integral Monte Carlo method. The model describes a rarefied system of spatially indirect excitons in a confining potential. Bose condensation in the system and its superfluid and structural properties are studied over a wide range of interparticle spatial correlations, from an almost ideal Bose gas to the regime of a strongly correlated system. It is found that, at strong interparticle spatial correlations, particles in the condensate form a crystal-like structure. In this case, the spatial correlations of particles in the condensate are less pronounced than the correlations of noncondensed particles. The effect of recurrent crystallization is observed in the regime of strong interparticle correlations.     

Structural Characterization of Graphene Nanosheets for Miniaturization of Potentiometric Urea Lipid Film Based Biosensors

The present article describes a miniaturized potentiometric urea lipid film based biosensor on graphene nanosheets. Structural characterization of graphene nanosheets for miniaturization of potentiometric urea lipid film based biosensors have been studied through atomic force microscopy (AFM) and transmission electron microscopy (TEM) measurements. UV‐Vis and Fourrier transform IR (FTIR) spectroscopy have been utilized to study the pre‐ and postconjugated surfaces of graphene nanosheets. The presented potentiometric urea biosensor exhibits good reproducibility, reusability, selectivity, rapid response times (～4 s), long shelf life and high sensitivity of ca. 70 mV/decade over the urea logarithmic concentration range from 1×10^?6 M to 1×10^?3 M.     

Fabrication of Sensitive Potentiometric Cholesterol Biosensor Based on Co3O4 Interconnected Nanowires

Highly sensitive, selective, reliable and inexpensive cholesterol biosensors are highly demanded for the routine monitoring of cholesterol molecules in order to prevent heart failure incidents. In this study, Co₃O₄ nanostructures are synthesized using polyvinyl pyrrolidone surfactant as growth template by a low temperature aqueous chemical growth method. The morphology of nanostructures was investigated by scanning electron microscopy and X‐ray diffraction techniques. The nanostructures exhibit interconnected nanowires like morphology with interconnected network of nanowires. The nanostructures of Co₃O₄ are polycrystalline. The cholesterol oxidase was physically adsorbed on the interconnected nanowires of Co₃O₄ for the chemical sensing of cholesterol molecules. The sensor device detected a wide range of cholesterol from 1×10^?7 M to 1×10^?3 M concentrations with sensitivity of ?94.031 mV/decade. A detection limit of 0.035×10^?7 M cholesterol concentration was observed and a fast response time of 10 s was also noticed. The fabricated device is highly stable, selective, sensitive, reproducible and repeatable. All the collected information about presented cholesterol biosensor indicates its potential application for the monitoring of cholesterol concentrations from human blood serum and real‐life samples.     

Dynamics of four-wave mixing on excitons in a quantum optical microcavity

A theory of degenerate four-wave mixing in a semiconductor optical cavity with quantum wells is constructed. The nonlinear response of a microcavity can be four to five orders of magnitude stronger than that of an isolated quantum well. For P ² E-and P ³-type nonlinearities the damped diffracted signal oscillates with a period determined by the Rabi splitting. For a biexcitonic mechanism of nonlinearity, the signal contains damped overtones of the Rabi splitting and the biexciton binding energy. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 11, 749–754 (10 December 1996)     

Surface recombination velocity in a silicon optical waveguide

Measurements of the varying infrared absorption by free carriers in a silicon waveguide during intermittent electron bombardment are used to study the surface recombination velocitys. The same values for s are obtained for heat-treated and untreated samples, which supports the theory that electron beam irradiation in itself has a dehydrating effect. Other experiments show thats is not dependent on the energy of the impinging electrons in the range 16–23 keV. Finally, the temperature dependence ofs in gold-doped silicon is estimated. Ifs is written in the forms=s ₀(293/T)^x,x is found to be 2.1±0.2 in the temperature interval 261K≦T≦309K.     

Absorption spectra versus field distribution for metal-dielectric three-dimensional photonic crystals

The absorption spectra of three-dimensional metal-dielectric photonic crystals (PCs) are studied using computer simulation by the finite difference time domain method and the layered Korringa-Kohn-Rostoker method. The band structure of a three-dimensional dielectric PC is obtained by the plane wave expansion method. The explanation of absorption spectra of PC based on its comparison with the band structure and Fabry-Perot resonances inside a PC plate is given. The intensity distribution of an electric field using FDTD inside the metal-dielectric PC for three various structures is analyzed. It is shown that spherical cavities in a dielectric PC “focus” the field inside cavities at certain wavelengths. This leads to an increase of absorption at these wavelengths if metal spheres are located in the centers of those cavities. This effect can be considered as an analogue of the Borrmann effect in X-ray spectroscopy.