The synthesis of MDMO-PPV capped PbS nanorods and their application in solar cells

Poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) capped PbS nanorods about 100 nm in diameter and 400 nm in length were synthesized via a hydrothermal route in toluene and dimethylsulfoxide solution. By blending the PbS nanorods with the MDMO-PPV as the active layer, bulk heterojunction solar cells with an indium tin oxide (ITO)/polyethylenedioxythiophene/polystyrenesulphonate (PEDOT PSS)/MDMO-PPV PbS nanorods/Al structure were fabricated in a N-2 filled glove box, Current density-voltage characterization of the devices showed that the solar cells with PbS nanorods hybrid with MDMO-PPV as active layer were better in performance than the devices with the polymer only. (C) 2009 Elsevier B.V. All rights reserved.

Synthesis and characterization of well-aligned Zn1-xMgxO nanorods and film by metal organic chemical vapor deposition

Well-aligned Zn1-xMgxO nanorods and film with Mg-content x from 0 to 0.051 have been successfully synthesized by metal organic chemical vapor deposition (MOCVD) without any catalysts. The characterization results showed that the diameters and lengths of the nanorods were in the range of 20-80 nm and 330-360 nm, which possessed wurtzite structure with a c-axis growth direction. As the increase of Mg precursor flows into the growth chamber, the morphology of Zn1-xMgxO evolves from nanorods to a film with scale-like surface and the height of the nanorods and the film was almost identical, it is suggested that the growth rate along the c-axis was hardly changed while the growth of six equivalent facets of the type {1 0 (1) over bar 0} of the Zn1-xMgxO has been improved. Photoluminescence and Raman spectra show that the products have a good crystal quality with few oxygen vacancies. With the Mg incorporation, multiple-phonon scattering become weak and broad, and the intensities of all observed vibrational modes decrease. And the ultraviolet near-band-edge emission shows a clear blueshift (x=0.051, as much as 90 meV) and slightly broadening compared with that of pure ZnO nanorods. (C) 2008 Elsevier B.V. All rights reserved.

One-step growth of ZnO from film to vertically well-aligned nanorods and the morphology-dependent Raman scattering

We observed a transition from film to vertically well-aligned nanorods for ZnO grown on sapphire (0001) substrates by metalorganic chemical vapor deposition. A growth mechanism was proposed to explain such a transition. Vertically well-aligned homogeneous nanorods with average diameters of similar to 30, 45, 60, and 70 nm were grown with the c-axis orientation. Raman scattering showed that the E-2 (high) mode shifted to high frequency with the decrease of nanorod diameters, which revealed the dependence of nanorod diameters on the stress state. This dependence suggests a stress-driven diameter-controlled mechanism for ZnO nanorod arrays grown on sapphire (0001) substrates. (c) 2005 American Institute of Physics.

Combined structure of ZnO vertical well-aligned nanorods and net-like structures on AIN/sapphire

ZnO vertical well-aligned nanorods were grown on A1N/sapphire by using metal-organic chemical vapor deposition. We first observed the ZnO net-like structures under the nanorods. The different strain was determined in these two layers by using double crystal X-ray diffraction, Raman spectra, which revealed that the nanorods were relaxed and the net-like structures were strained. The optical properties of two layers were measured by using the cathodoluminescence and photo luminescence and the shift of UV peaks was observed. Moreover, the growth mechanism of the ZnO nanorods and the net-like structures is discussed. (c) 2007 Elsevier B.V. All rights reserved.

Synthesis and characterization of ZnO nanorods and nanoflowers grown on GaN-based LED epiwafer using a solution deposition method

We report the growth of hexagonal ZnO nanorods and nanoflowers on GaN-based LED epiwafer using a solution deposition method. We also discuss the mechanisms of epitaxial nucleation and of the growth of ZnO nanorods and nanoflowers. A GaN-based LED epiwafer was first deposited on a sapphire substrate by MOCVD with no electrode being fabricated on it. Vertically aligned ZnO nanorods with an average height of similar to 2.4 mu m were then grown on the LED epiwafer, and nanoflowers were synthesized on the nanorods. The growth orientation of the nanorods was perpendicular to the surface, and the synthesized nanoflowers were composed of nanorods. The micro-Raman spectra of the ZnO nanorods and nanoflowers are similar and both exhibit the E-2 (high) mode and the second-order multiple-phonon mode. The photoluminescence spectrum of ZnO nanostructures exhibits ultraviolet emission centred at about 380 nm and a broad and enhanced green emission centred at about 526 nm. The green emission of the ZnO nanostructures combined with the emission of InGaN quantum wells provides a valuable method to improve the colour rendering index (CRI) of LEDs.

Strain-induced anodization of SiGe/Si multiple layers to form high density SiGe/Si heterogeneous nanorods

Nation Natural Science Foundation of China 50672079 60676027 60837001 60776007; National Basic Research Program of China (973 Program) 2007CB613404; China-MOST International Sci & Tech Cooperation and Exchange 2008DFA51230

Influence of nitridation time on the morphology of GaN nanorods synthesized by nitriding Ga2O3/ZnO films

Gallium nitride (GaN) nanorods were synthesized by nitriding Ga2O3/ZnO films which were deposited in turn on Si (111) substrates using radio frequency (RF) magnetron sputtering system. In the nitridation process, ZnO was reduced to Zn and Zn sublimated at 950 degrees C. Ga2O3 was reduced to Ga2O and Ga2O reacted with NH3 to synthesize GaN nanorods with the assistance of the sublimation of Zn. The morphology and structure of the nanorods were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED). The composition of GaN nanorods was studied by Fourier-transform infrared spectrophotometer (FTIR). The synthesized nanorods is hexagonal wurtzite structured. Nitridation time of the samples has an evident influence on the morphology of GaN nanorods synthesized by this method. (c) 2006 Elsevier B.V. All rights reserved.

Electronic structure and g factors of narrow-gap zinc-blende nanowires and nanorods

The Hamiltonian in the framework of eight-band effective-mass approximation of the zinc-blende nanowires and nanorods in the presence of external homogeneous magnetic field is given in the cylindrical coordinate. The electronic structure, optical properties, magnetic energy levels, and g factors of the nanowires and nanorods are calculated. It is found that the electron states consist of many hole-state components, due to the coupling of the conduction band and valence band. For the normal bands which are monotone functions of |k(z)|, long nanorods can be modeled by the nanowires, the energy levels of the nanorods approximately equal the values of the energy band E(k(z)) of the nanowires with the same radius at a special k(z), where k(z) is the wave vector in the wire direction. Due to the coupling of the states, some of the hole energy bands of the nanowires have their highest points at k(z)=0. Especially, the highest hole state of the InSb nanowires is not at the k(z)=0 point. It is an indirect band gap. For these abnormal bands, nanorods can not be modeled by the nanowires. The energy levels of the nanorods show an interesting plait-like pattern. The linear polarization factor is zero, when the aspect ratio L/2R is smaller than 1, and increases as the length increases. The g(z) and g(x) factors as functions of the k(z), radius R and length L are calculated for the wires and rods, respectively. For the wires, the g(z) of the electron ground state increases, and the g(z) of the hole ground state decreases first, then increases with the k(z) increasing. For the rods, the g(z) and g(x) of the electron ground state decrease as the R or the L increases. The g(x) of the hole ground state decreases, the g(z) of the hole ground state increases with the L increasing. The variation of the g(z) of the wires with the k(z) is in agreement with the variation of the g(z) of the rods with the L.

Porous ZnAl2O4 spinel nanorods doped with Eu3+: synthesis and photoluminescence

Eu3+-doped zinc aluminate (ZnAl2O4) nanorods with a spinel structure were successfully synthesized via an annealing transformation of layered precursors obtained by a homogeneous coprecipitation method combined with surfactant assembly. These spinel nanorods, which consist of much finer nanofibres together with large quantities of irregular mesopores and which possess a large surface area of 93.2 m(2) g(-1) and a relatively narrow pore size distribution in the range of 6 - 20 nm, are an ideal optical host for Eu3+ luminescent centres. In this nanostructure, rather disordered surroundings induce the typical electric-dipole emission (D-5(0) --> F-7(2)) of Eu3+ to predominate and broaden.

Study on the Raman spectra of GaP nanorods synthesized within carbon nanotube templates

The Raman spectra of GaP nanorods grown in carbon nanotube templates have been reported. The red shifts of the TO and LO modes were observed due to phonon confinement effect in GaP nanorods. The measured red shifts range from 2 to 10cm(-1) depending on the size of the measured nanorods. It has been found that the polarization properties, which cannot be well explained by the selection rules of single nanorod, result from the direction disorder of nanorods in the measured area. The more the disorder is, the weaker the directionality of polarization properties is. The decrease of the Raman frequency of the TO and LO mode of the nanorods with the increasing power of the exciting laser suggests that the heating effect of the nanorods is far stronger than the bulk material. In addition, the saturation and then decrease of the Raman intensity with the increasing laser power indicate the rapid increase of the defects in the nanorods exposed to a strong exciting laser.

Raman spectra of SiC nanorods with different excitation wavelengths

With increasing excitation wavelength from 514 to 782 mn, a significant difference in the Raman spectra of SIC nanorods was observed as compared to bulk material. The intensity ratio of the LO mode to that of the IF mode increases with the excitation wavelength increasing. This has been identified as resonant Raman scattering caused by Frohlich interaction.

Effect of defects on optical phonon Raman spectra in SiC nanorods

Fabricated one-dimensional (1D) materials often have abundant structural defects. Experimental observation and numerical calculation indicate that the broken translation symmetry due to structural defects may play a more important role than the quantum confinement effect in the Raman features of optical phonons in polar semiconductor quantum wires such as SiC nanorods, (C) 1999 Elsevier Science Ltd. All rights reserved.

Synthesis of GaN nanorods with vertebra-like morphology

GaN nanorods with vertebra-like morphology were synthesized by nitriding Ga2O3/ZnO films at 1000 degrees C for 20min. Ga2O3 thin films and ZnO middle layers were pre-deposited in turn on Si(111) substrates by r.f. magnetron sputtering system. In the flowing ammonia ambient, ZnO was reducted to Zn and Zu sublimated at 1000 degrees C. Ga2O3 was reducted to Ga2O and Ga2O reacted with NH3 to synthesize GaN nanorods in the help of the sublimation of Zn. The structure and morphology of the nanorods were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), The composition of GaN nanorods was studied by energy dispersive spectroscopy (EDS) and fourier transform infrared (FTIR) system.

Influence of interface modification on the performance of polymer/Bi2S3 nanorods bulk heterojunction solar cells

In this paper, bulk heterojunction photovoltaic devices based on the poly[2-methoxy-5-(3',7'-dimethyloctyloxy)- 1,4-phenylenevinylene] (MDMO-PPV):Bi2S3 nanorods hybrid material were present. To optimize the performance of the devices, the interface modification of the hybrid material that has a significant impact on the exciton dissociation efficiency was studied. An improvement in the device performance was achieved by modifying the Bi2S3 surface with a thin dye layer. Moreover, modifying the Bi2S3 surface with anthracene-9-carboxylic acid can enhance the performance further. Compared with the solar cells with Bi2S3 nanorods hybrid with the MDMO-PPV as the active layer, the anthracene-9carboxylic acid modified devices are better in performance, with the power conversion efficiency higher by about one order in magnitude.

Ferromagnetic MnSb Films Consisting of Nanorods and Nanoleaves

Ferromagnetic MnSb films were synthesized on Si wafers by physical vapor deposition. X-ray diffraction revealed that the films primarily consisted of MnSb alloy. Nanorods and nanoleaves were observed in the MnSb films by field-emission scanning electron microscopy. These nanorods had an average diameter of 20nm and a length of up to hundreds of nanometers. The nanoleaves had a width and thickness of about 100 and 20nm, respectively. Magnetic hysteresis loops were measured by an alternative gradient magnetometer, and the loops showed strong geometrical anisotropy.