Structural Characteristics and Photoluminescence of Zinc Oxide Nanocrystals

We have prepared zinc oxide nanocrystals using a new type of solid-state reaction.The nanosized grains were obtained by changing the heat treatment temperature and the sizes were determined to be from 10 to 42 nm.The lattice vibrational Raman spectra were measured and assigned at different grain sizes.We observed a strong visible emission centred at 580 nm in the nanosized ZnO at room temperature.We have investigated the photoluminescence properties under different grain sizes after annealing.The weakening of the luminescence is attributed to the decrease of intrinsic structural defects,mainly,oxygen vacancies and the increase of the grain size in the nanocrystals.     

Growth of Zinc Oxide Thornballs by a Novel Method

Thornballs of zinc oxide (ZnO) is firstly synthesized by a simple solid vapour deposition process under lead oxide (PbO) atmosphere. The micro-thornballs were constituted by numerous needles, which extend outwards in all directions symmetrically. The balls have the dimensions of 120μm in diameter, while the average diameter of the needles was about lO0-200nm. The needles on the balls grow along the (0001) orientation and have gradient cross-sectional radii. Control experiments proved that PbO plays an important role in the growth. The excitationemission measurement exhibits that the synthesized ZnO thornballs possess intensive photoluminescence property, which provides the evidence that PbO does not deteriorate the optical properties of ZnO thornballs.     

Luminescence with Local Distribution and Its Possible Mechanism in Zinc Oxide Micro-Crystallites

The spatial luminescence distribution hi the ZnO micro-crystallite fihns deposited on silicon substrates by CVD at room tempezature is investigated by the cathedolumineseence （CL） image. It has been observed that the CL image of the samples constitutes a certain pattern. The UV emission pattern projective to the （0001） face of ZnO grains consists of a series of lines nearby the grain boundaries . The included angles between any two adjacent lines are almost 120°. What is more, some luminescent lines form a close hexagon similar to ZnO crystalline structure. Such a local distribution propety shows that the UV emission on as-grown ZnO crystallite should be due to some local defects congregated to {1010} facets of ZnO grain rather than free exciton recombination.     

Thermally Stimulated Electron–Hole and Ionic Processes in Zinc Oxide Crystals

The principal results of the investigation of thermally stimulated electron–hole and ionic processes in hydrothermal and gas-phase ZnO single crystals preexcited at low temperatures, based on simultaneous study of photo-EPR and thermoluminescence (TL), are presented. The nature of the traps determining the TL peaks at 17, 24, 40, 53, 90–110, 140–150, and 160–200 K is discussed. In particular, it has been established that the lithium paramagnetic centers (Li_Zn ⁺–O^I) play the role of hole traps in ZnO giving green and red TL in the temperature range 160–200 K and, in the case of association with small-sized donors, also TL in the temperature range 90–110 K. The other traps are electronic in character, and in the presence of acceptor lithium in the crystals, they form yellow-orange TL. Optical quenching of TL has been evaluated, and it has been found that there is a difference E 0.75 eV between the thermal and optical energies of ionization of lithium acceptors. Irreversible ionic processes associated with the healing of cationic vacancies at T 360–420 K have been revealed.     

Effect of Ultraviolet Light on Hybrid Zinc Oxide Polymer Bulk Heterojunction Solar Cells

Compared to conjugated polymer poly[2-methoxy-5-（3＇ ,7＇-dimethyloctyloxy）-l,4-phenylenevinylene] （MDMO-PPV） solar cells, bulk heterojunction solar cells composed of zinc oxide （ZnO） nanocrystals and MDMO-PPV have a better energy conversion efficiency. However, ultraviolet （UV） light deteriorates the performance of solar cells composed of ZnO and MDMO-PPV. We propose a model to explain the effect of UV illumination on these ZnO：MDMO-PPV solar cells. According to this model, the degradation from UV illumination is due to a decrease of exciton dissociation efficiency. Our model is based on the experimentM results such as the measurements of current density versus voltage, photoluminescence, and photocurrent.     

Optical Spectra of Zinc Oxide in the Wide Energy Range 0–30 eV

A full set of spectra of the optical functions of a zinc oxide crystal in the range 0–30 eV has been calculated on the basis of the experimental spectrum of characteristic losses –Im ^–1. The ₂, ₁ and Im ^–1, Re ^–1 spectra were decomposed into elementary components. The most intense transverse and longitudinal components of transitions and their parameters have been determined. The data obtained were compared with theoretical calculations of the bands.     

Enhanced Upconversion Luminescence of Erbium–Nitrogen-Doped Zinc Oxide Nano-Wires by Implantation of Ytterbium Ions

Erbium–nitrogen codoped zinc oxide nanowires of ytterbium-doped are prepared by thermal evaporation and ion implantation methods. Ytterbium ions are doped into nanowires at a fluence of (0, 1, 3, 5, and 9) × 10¹⁵ cm^?2. Microstructural and optical properties of specimen are investigated by X-ray diffractometer, absorption spectra, Raman, and upconversion photoluminescence examinations. Upconversion photoluminescence emissions at 550 nm and 660 nm are obtained under 980-nm light excitation. Both intensities of green and red peaks are enhanced by the introduction of ytterbium ions. When ytterbium ion fluence is 5 × 10¹⁵ cm^?2, light emission intensity reaches maximum value. The energy transfer and cross-relaxation processes are responsible for the change of emission intensity.     

Improved Voltage and Fill Factor by Using Zinc Oxide Thin Film as a Barrier Layer in Dye-Sensitized Solar Cells

A series of dye-sensitized solar cells based on ZnO-modified TiO2 nano-porous films have been prepared. The current-voltage characteristics of the cells show that the ZnO-modification can improve the open-circuit voltage and the fill factor but can decrease the short-circuit current. Dark current and transient photovoltage measurements are used to study the back reaction. It is indicated that the recombination process is suppressed by blocking the hole transporting from the nano-porous TiO2 since the surface of the semiconductor is almost fully covered with ZnO as a barrier layer.     

The 6th International Workshop on Zinc Oxide and Related Materials Aug. 5～7,Changchun,China 2nd Announcement

<正>Dear Colleague:We are pleased to announce that "The 6th International Workshop on Zinc Oxide and Related Materials"     

Effects of Poly(Propylene Oxide)–Poly(Ethylene Oxide)–Poly(Propylene Oxide) Triblock Copolymer on the Gelation of Poly(Ethylene Oxide)–Poly(Propylene Oxide)–Poly(Ethylene Oxide) Aqueous Solutions

Poly(ethylene oxide)-poly(propylene oxide)–poly(ethylene oxide) ((EO)_n–(PO)_m–(EO)_n) block copolymers, commercially available as Pluronics (BASF Corp.) and Poloxamers (ICI Corp.), have been widely applied in medicine, biochemistry, and other fields because of their ability to form reversible micelles and physical gels in aqueous solution. Generally, for PEO–PPO–PEO block copolymers with higher ethylene oxide concentration, the micellization and gelation in aqueous solution are easier. However, if we introduce the reverse block copolymer PPO–PEO–PPO into PEO–PPO–PEO aqueous solutions, the micellization and gelation of the system will be more complex. In this work, the reverse block copolymer PO₁₄–EO₂₄–PO₁₄ (17R4) was added to the Pluronics EO₂₀–PO₇₀–EO₂₀ (P123), EO₁₀₀–PO₆₅–EO₁₀₀ (F127), and EO₁₃₃–PO₅₀–EO₁₃₃ (F108) aqueous solutions with different molar ratios. The rheological properties of different mixtures were measured to study the additive effect on the gelation behavior. The sol–gel transition temperature of the P123, F127, and F108 solutions shifted to a higher temperature when 17R4 was added to the solutions. In addition, the existence of 17R4 greatly affected the stability of gels. These results help to better understand the gelation of Pluronic aqueous solutions.     

Analytical Study of Raw Materials of Zinc Oxide Used for Enamels on Industrial Ceramics: Quantitative Analysis of Zinc,Lead, and Sulfur in These Samples by X‐ray Fluorescence and Flame Atomic Absorption Spectrometry

An analytical study is carried out to optimize X‐ray fluorescence (XRF) and flame atomic absorption spectrometry (FAAS) quantitative analysis of Zn, Pb, and S in ZnO samples commonly used to obtain industrial ceramic enamels. Pb and S in the raw materials often contaminate ZnO and are very detrimental in industrial applications. Thus, very accurate analytical determination of these elements in ceramic samples is extremely important. First of all, a mineralogical study by X‐ray diffraction (XRD) on the different components in these raw materials and the materials produced during the firing process is performed in order to establish the mineral forms in a reference sample for analysis by XRF spectrometry. The working conditions are optimized for XRF multielemental analysis, using the sample in the form of pellets, due to high loss on ignition (LOI) values. The preparation of suitable standards and working conditions for FAAS analysis have also been optimized. The content of these elements was determined by FAAS for the reference sample and several samples for industrial use, and the results were compared with those obtained by XRF. Comparison of the results obtained from XRF and FAAS analysis of Pb and Zn show more accurate values for FAAS. For ZnO, an accuracy of 0.11% with ±0.1% precision by FAAS and 0.46% accuracy with ±0.2% precision by XRF are found. For PbO, 1.06% accuracy and ±0.06% precision using FAAS and 5.6% accuracy and ±0.35% precision by XRF were found. For SO₃ determined only by XRF, accuracy was 4.76% with ±0.25% precision. These values are highly satisfactory given that these two elements are only found in small proportions.     

The Zinc–Sulfide Exciton Spectra

The exciton spectra of optical functions of hexagonal zinc, sulfide are calculated at 77 K using experimental reflectance spectra. The oscillator energies and forces are determined for three main exciton bands with the quantum number n = 1 for E c and E c polarizations. The energies of spin-orbit and off-axis crystal splitting for the upper w-ZnS valence bands are also determined.     

OH− ions in Oxide Crystals

This article reviews the spectroscopic properties of hydrogen bound to a large variety of synthetic compounds like simple oxides, perovskites, the LiNbO₃ family, KTP, sillenites, eulytites, borates, garnets, spinels and some others. In almost all compounds the OH stretch mode is found in the range 3200-3700 cm^?1, with isotope replica of deuterium (2350-2750 cm^?1) and a few examples of tritium (2050-2250 cm^?1). The fundamental vibration, the isotope replica and the corresponding overtones are described with an anharmonic oscillator model. A nonlinear relation between the anharmonicity and the harmonic frequency is found and interpreted using recent second order perturbation calculations. An often pronounced temperature dependence of the stretch mode and phonon coupling is discussed. Data for the stretching vibration influenced by additional weak or strong doping are presented. Atomistic defect models are described and tested by means of light polarization, external perturbations like pressure and electric field, and Raman scattering analyzed with the behavior-type method. The last section briefly reviews applications profiting from doping with hydrogen and its easy detection by means of the OH stretch mode.     

The 6th International Workshop on Zinc Oxide and Related Materials Aug.5～7,2010,Changchun,China First Announcement and Call for Papers

Dear Colleague:It is our great pleasure to announce that"The 6th International Workshop on Zinc Oxide and Related     

The 6th International Workshop on Zinc Oxide and Related Materials Aug.5～7,2010,Changchun,China First Announcement and Call for Papers

<正>Dear Colleague:It is our great pleasure to announce that "The 6th International Workshop on Zinc Oxide and Related Materials" (6th ZnO Workshop) will be held by The Key Laboratory of Excited State Processes,Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,on August 5～7,2010 in Changchun,China.     

Fluorescence Microscopy of Nanoscale Silver Oxide Thin Films

The experimental conditions for photoactivated intermittent fluorescence from nanoscale silver oxide were studied with fluorescence microscopy.Strong fluorescence was observed from the Ag2O particles with size of 10-20nm excited with both blue and green light .We observed the saturation of Photoexcitation with blue light and explained the experimental results using the model of agglomeration of silver atoms to form small clusters and the fluorescence of Ag2 and Ag3 clusters.     

Up-Conversion Luminescence of a High Soluble Zinc Phthalocyanine-Epoxy Derivative

Synthesis and photoelectric properties of a high soluble zinc phthalocyanine-epoxy derivative are investigated. The derivative can be solubilized in convenient solvents, such as Ctt30tt, Ctt3Ctt20tt and H2O. The fluorescence and UV-visible analyses indicate that the ZnPc-epoxy derivative still maintains the plane structure which comesfrom Zn(4,4′,4″,4-ta)Pc and the derivative has obvious up-conversion luminescence in room temperature. The up-conversion luminescence can be explained by the selection rule depending on the two-photon absorption.     

Optical Properties and Structure Analyses of Zinc Sulfide Nanorods

ZnS nanorods were synthesized using solvothermal process with ethylenediamine as a bidentate ligand to form Zn^2 complexes and dodecylthiol providing an effective control over the crystal growth of ZnS nanorod. The microstructure of the nanorods was characterized by x-ray diffraction and transmission-electron microscopy. The optical properties of ZnS nanorods were examined by the photoluminescence spectrum.     

Oxide magnetic semiconductors： Materials, properties, and devices

We give a brief introduction to the oxide （ZnO, TiO2, In2O3, SnO2, etc.）-based magnetic semiconductors from fundamental material aspects through fascinating magnetic, transport, and optical properties, particularly at room temperature, to promising device applications. The origin of the observed ferromagnetism is also discussed, with a special focus on first-principles investigations of the exchange interactions between transition metal dopants in oxide-based magnetic semiconductors.     

Band Structure of the Non—Oxide Perovskite MgCNi3

Using the self-consistent full-potential linearized augmented plane wave method,we carry out the electronic structure calculations of MgCNi3 in the local spin density approximation(LSDA) of the density-functional theory.The LSDA solution is metal.The magnetic moment on the Ni ion is only 0.014uB.There is a peak in the density of state just below the Fermi energy(Ef),which can be strongly correlated with various instabilities.After including the strong electron-electron correlation effects on the Ni 3d state by the on-site Coulomb interaction correction,the density of state is greatly redistributed.and the peak just below Ef disappears.The magnetic moment on the Ni ion becomes 0.66uB.Both LSDA and LSDA U have shown that the electroic states near the Fermi surface are dominated by the 3d orbital of Ni.