Spin currents in diluted magnetic semiconductors (extended version)

Spin currents resulting in the zero-bias spin separation have been observed in unbiased diluted magnetic semiconductor structures (Cd,Mn)Te/(Cd,Mg)Te. The pure spin current generated due to the electron gas heating by terahertz radiation is converted into a net electric current by application of an external magnetic field. We demonstrate that polarization of the magnetic ion system enhances drastically the conversion due to the spin-dependent scattering by localized Mn(2+) ions and the giant Zeeman splitting.Comment: 6 pages, 4 figure

Bioconjugation of Silver Nanowires with Photosynthetic Light-Harvesting Complexes

We demonstrate a way to conjugate a light-harvesting complex, peridinin-chlorophyll-protein, with silver nanowires using biotin-streptavidin linker. In the case of conjugated structure we observe slight increase of the fluorescence intensity of the chlorophyll emission followed by the gradual decrease of the intensity due to photobleaching. For a non-conjugated mixture of peridinin-chlorophyll-protein with silver nanowires only the photobleaching takes place. The results suggest a possible way to fabricate hybrid nanostructures comprising light-harvesting complexes and metallic nanoparticles for achieving the efficient plasmon-induced enhancement of absorption of the light-harvesting complexes

Bioconjugation of Silver Nanowires with Photosynthetic Light-Harvesting Complexes

We demonstrate a way to conjugate a light-harvesting complex, peridinin-chlorophyll-protein, with silver nanowires using biotin-streptavidin linker. In the case of conjugated structure we observe slight increase of the fluorescence intensity of the chlorophyll emission followed by the gradual decrease of the intensity due to photobleaching. For a non-conjugated mixture of peridinin-chlorophyll-protein with silver nanowires only the photobleaching takes place. The results suggest a possible way to fabricate hybrid nanostructures comprising light-harvesting complexes and metallic nanoparticles for achieving the efficient plasmon-induced enhancement of absorption of the light-harvesting complexes

The Effect of Surface Preparation on Physical Properties of Ni-ZnSe Junctions

We report on optical and photovoltaic properties of Ni-ZnSe junctions. We demonstrate that the preparation method of the ZnSe surface determines luminescence, optical transmission of ZnSe substrates and photovoltaic spectra of the Ni-ZnSe junctions. The observed effects are explained by formation of low-dimensional quantum structures on the ZnSe surface in result of the surface preparation procedure. This is confirmed by atomic force microscopy studies, which show the presence of grains with lateral dimensions of 30-300 nm on ZnSe surface. The smallest grains are responsible for a wide spectral band observed in photoluminescence at 3.4 eV, i.e., at much higher energies than the energy gap of bulk ZnSe, $E_{g}$ ≈ 2.7 eV

Gold Nanoparticles with Elongated Shapes: Synthesis and Optical Properties

We use a seed-mediated growth to fabricate gold nanorods in water solution. By changing the amount of silver salt we demonstrate the control of aspect ratio of the obtained rods. The microscopic and spectroscopic analyses provide ways to characterize the morphology and the optical properties of the gold nanorods. Nanorods synthesized using this approach feature length of the order of 50-60 nm, which translates into longitudinal plasmon resonances in the near infrared spectrum region

Gold Nanoparticles with Elongated Shapes: Synthesis and Optical Properties

We use a seed-mediated growth to fabricate gold nanorods in water solution. By changing the amount of silver salt we demonstrate the control of aspect ratio of the obtained rods. The microscopic and spectroscopic analyses provide ways to characterize the morphology and the optical properties of the gold nanorods. Nanorods synthesized using this approach feature length of the order of 50-60 nm, which translates into longitudinal plasmon resonances in the near infrared spectrum region

Anharmonic Optical Phonon Effects in ZnO Nanocrystals

Zinc oxide (ZnO) is a very promising material for optoelectrical devices operating at the short-wavelength end of the visible spectral range and at the near UV. The Raman scattering studies of ZnO heterolayers formed by isothermal annealing show sharp phonon lines. In addition to the A$\text{}_{1}$(TO), E$\text{}_{1}$(TO), E$\text{}_{2}^{H}$, and E$\text{}_{1}$(LO) one-phonon lines, we observed two-phonon lines identified as: E$\text{}_{2}^{H}$ - E$\text{}_{2}^{L}$, E$\text{}_{2}^{H}$ + E$\text{}_{2}^{L}$, and 2LO at 332, 541, and 1160 cm$\text{}^{-1}$, respectively (at room temperature). The identification of the E$\text{}_{2}^{H}$ - E$\text{}_{2}^{L}$ peak was confirmed by its thermal dependence. Temperature dependent measurements in the range 6-300 K show that the phonon frequencies decrease with temperature. The E$\text{}_{2}^{H}$ peak is at energy 54.44 meV (439.1 cm$\text{}^{-1}$), at 4 K and due to phonon-phonon anharmonic interaction, its energy decreases to 54.33 meV (438.2 cm$\text{}^{-1}$) at room temperature. The Grüneisen parameter found for this oscillation mode was γ$\text{}_{E}$ 2H = 1.1 at about 300 K. The intensity of the E$\text{}_{2}^{H}$ - E$\text{}_{2}^{L}$ peak increases strongly with temperature and this dependence can be described by the Bose-Einstein statistics with activation energy of 13.8 meV (nearly equal to the energy of the E$\text{}_{2}^{L}$ phonon)

Anharmonic Optical Phonon Effects in ZnO Nanocrystals

Zinc oxide (ZnO) is a very promising material for optoelectrical devices operating at the short-wavelength end of the visible spectral range and at the near UV. The Raman scattering studies of ZnO heterolayers formed by isothermal annealing show sharp phonon lines. In addition to the A$\text{}_{1}$(TO), E$\text{}_{1}$(TO), E$\text{}_{2}^{H}$, and E$\text{}_{1}$(LO) one-phonon lines, we observed two-phonon lines identified as: E$\text{}_{2}^{H}$ - E$\text{}_{2}^{L}$, E$\text{}_{2}^{H}$ + E$\text{}_{2}^{L}$, and 2LO at 332, 541, and 1160 cm$\text{}^{-1}$, respectively (at room temperature). The identification of the E$\text{}_{2}^{H}$ - E$\text{}_{2}^{L}$ peak was confirmed by its thermal dependence. Temperature dependent measurements in the range 6-300 K show that the phonon frequencies decrease with temperature. The E$\text{}_{2}^{H}$ peak is at energy 54.44 meV (439.1 cm$\text{}^{-1}$), at 4 K and due to phonon-phonon anharmonic interaction, its energy decreases to 54.33 meV (438.2 cm$\text{}^{-1}$) at room temperature. The Grüneisen parameter found for this oscillation mode was γ$\text{}_{E}$ 2H = 1.1 at about 300 K. The intensity of the E$\text{}_{2}^{H}$ - E$\text{}_{2}^{L}$ peak increases strongly with temperature and this dependence can be described by the Bose-Einstein statistics with activation energy of 13.8 meV (nearly equal to the energy of the E$\text{}_{2}^{L}$ phonon)

Raman scattering studies of MBE-grown ZnTe nanowires

4th MAG-EL-MAT Members Meeting 2006, Bellewo, POLAND, MAY 03-06, 2006International audienceWe report on the first studies of the optical properties of MBE-grown ZnTe nanowires (NWs). The growth of ZnTe NWs was based on the Au-catalyzed vapour-liquid-solid mechanism and was performed on (001), (011), or (111)B-oriented GaAs substrates. Investigated NWs have a zinc-blende structure, the average diameter of about 30 nm, and typical length between 1 and 2 mu m. Their growth axes are oriented along -type directions of the substrate. The structural characterization of the NWs was performed by means of X-ray diffraction, using the synchrotron radiation corresponding to the wavelength of CuK(alpha 1) radiation W1 beamline at Hasylab DESY). The macro-Raman spectra of either as-grown NWs on GaAs substrate or of NWs removed from substrate and deposited onto Si were collected at temperatures from 15 K to 295 K using Ar(+) and Kr(+) laser lines. Strong enhancement of ZnTe-related LO-phonon structure was found for an excitation close to the exciton energy. Our studies revealed also the presence of small trigonal Te precipitates, typical of tellurium compounds