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The luminescence excitation spectra, luminescence spectra and the nanosecond-scale decay kinetics were studied. The ZnO and ZnO:Al nanopowders were prepared by vaporization-condensation in a solar furnace using different raw powders: commercial, hydrothermal and those obtained by plasma synthesis. Exciton-phonon as well as exciton-exciton interaction processes in nanopowders, a bulk crystal and ZnO ceramics were studied and compared. The fast decay and low afterglow intensity of ZnO nanopowders and ceramics support these materials for scintillators. Index Terms--Ceramic, fast luminescence, nanopowders, ZnO.

A standard ion-exchange technique was used for the fabrication of channel optical waveguides in novel Er-doped and Er-Yb co-doped ZnO-containing silicate glasses. Findings reveal the simulation of very large net optical gain for an ideal overlap of the pump and signal optical field in a glass containing at 3% of Er and no Yb.

The third harmonic generation technique is employed to explain the results of the third order nonlinear optical susceptibilities of various doped and undoped zinc oxide films. The results show that the conversion of the third harmonic signal at different dopants and at an appropriate concentration takes place due to the high conductivity, morphology and the crystalline quality of the films.

The structural properties of the ZnO thin films, which are epitaxially deposited on sapphire substrates at different temperatures, were studied using the technique of pulsed laser deposition (PLD). The findings indicated that oxygen vacancies play the most important role in the deep-level (DL) emissions in such films, as it highly reduced the surface roughness, as well as the transmittance.

The properties of nominally undoped ZnO films, which are deposited by reactive sputtering on the lightly boron-doped([p.sup.-]) and heavily boron-doped([p.sup.+]) silicon substrates, are studied. The analysis reveals that the ZnO/[p.sup.+]-Si hetereojunctions are electroluminescent to a certain extent in the visible region, whereas the ZnO/[p.sup.-]-Si heterojunctions does not exhibit this property.

The effect of surface conductivity on the ZnO-coated surface barrier discharge in open air is examined. Optical emission spectroscopy is used to analyze the difference of plasma transition between normal dielectric barrier discharge (DBD) and ZnO-coated DBD.

The pulsed laser deposition technique is used to study the composite ZnO/Ce[O.sub.2] thin films grown epitaxially on r-sapphire substrates. It is suggested that the Ce[O.sub.2] buffer layer acts as an efficient barrier against the diffusion of aluminium from the sapphire substrate into the ZnO layer.

Piezoelectric force microscopy (PFM) is used to measure the crystal orientation and piezoelectric properties of solution grown ZnO nanorods on Ag films. The rod-to-rod variation is not due to sample topography, but it is speculated that conduction electrons arising from defects and impurities are responsible for the reduced piezoelectric responses in the nanorods.

Study makes use of the pulsed layer deposition on c-axis oriented sapphire substrates for the development of epitaxcial ZnO films codoped with tellurium and nitrogen, which are extremely useful in the production of ZnO based light-emitters. The results show that doping of ZnO highly reduces the carrier lifetime in such emitters, as compared to the undoped ones.

The luminescence properties of zinc oxide (ZnO) films developed by pulsed laser deposition were examined by photoluminescence spectroscopy. The findings suggested that the existence of an interference effect in ZnO films was confirmed by systematically checking the variation in the photoluminescence spectra with film thickness.

A study obtained ZnO nanocrystals doped with Cd, Mg, Mn, and Fe ions by thermolysis of a family of metal cupferrates. The band gap of the nanocrystal could be tuned in the range of 2.9-3.8 eV by the use of the dopants.

The synthesis of uniform ellipsoidal ZnO particles in an aqueous solution in the presence of triethonalamine (TEA) mediated by sonication at the temperature below 80 degree Celsius is described. The morphologies of the ZnO particles could be systematically controlled from elongated rugby ball-like ellipsoidal to half-ellipsoidal by increasing the TEA concentration.

A study prepared Al doped ZnO (AZO) films with varying fluorine content by radio frequency magnetron sputtering at a room temperature to investigate doping effects of fluorine on the structural, the optical, and the electrical properties. The small amount of fluorine addition to AZO films resulted in beneficial effect on the electrical conductivity by improving the direct current Hall mobility, and the minimum specific resistivity is as low as 5.9 x [10.sup.-4] [omega] cm.

The strain-induced defects and their effects on structural and optical properties in ZnO epitaxial layers deposited on SiC substrates are demonstrated. It is learnt that the biaxial strain in ZnO/SiC heterostructure is the main driving force for generation of defects, together with impurities and imbalanced interfaces.

Zinc oxide (ZnO) tetrapodlike nanostructures are synthesized by thermal evaporation of Zn powder at different flow rates of argon. As the flow rate increases, nano-ZnO morphology changes from an initial mixture of tetrapod, nanowire, nanosheet, and nanodendritic forms to a uniform tetrapodlike morphology.

The first large-scale synthesis of unusual ZnO ellipsoids by a facile solution process and their optical properties are reported. The results have shown that these self-assembled microstructures composed of nanoparticles and orientationally aligned nanorods are formed by the oriented-attachment mechanism.

A theoretical study about free-excitonic gain of wurtzite ZnO-[Mg.sub.x][Zn.sub.1-x]O quantum wells (QWs) is presented. The findings suggest that the free-excitonic gain could be maximized for x values between 0.27 and 0.30, if well width is chosen to be 15 Angstrom.

The influence of postgrowth annealing on the structural and optical properties of rf cosputtered Mn doped ZnO thin films deposited on glass substrate at room temperature is investigated. The optical dispersion of refractive index with photon energy in Z[n.sub.1-x]M[n.sub.x]O films varying x and different annealing temperature is studied in the light of single oscillator and Pikhtin-YasEkov.

Characteristics of laser-produced ZnO plasmas are investigated by spectroscopic observations. The ablation dynamics and recombination process in vacuum or gas atmospheres (helium or oxygen) are studied on the basis of atomic physics.

In this study, we integrated zinc oxide nanomaterials, which possess a high surface-to-volume ratio and take part in specific interactions with organic functional groups, into infrared sensing devices to improve both the sensitivity and selectivity of the detection of volatile organic compounds (VOCs). An annealing method was developed to modify ZnO nanoparticles directly onto the surface of an IR internal reflection element. The ZnO nanoparticles produced this way are spherical (diameters, ~20 nm). When this modified sensing element was used to detect VOCs, intense IR signals for compounds bearing polar functional groups were observed. The conditions for preparing the ZnO nanoparticles for IR sensing of VOCs were optimized by varying such factors as the volume of the coating zinc solution, the calcination temperature, and calcination time. After mapping the IR signals obtained with respect to these factors, the optimal IR signal from this modified IR sensing element occurred when using 100 [micro]L of zinc solution and performing the calcination at 400 [degrees]C for at least 30 min. VOCs having different functional groups were used to characterize the behavior of the ZnO-modified sensing element; our results indicate that the selectivity of this device favors polar compounds. Based on detection of several polar VOCs, the results indicate that quantitative analysis is possible when using the ZnO nanoparticle-modified sensor; in some cases, the detection limit was below an injected sample volume of 0.5 nL (~2.2 ppm), with a linear regression coefficient ([R.sup.2]) above 0.99 when up to 0.3 [micro]L of sample (~1400 ppm) was injected to a 100 mL of sample cell.

One-dimensional (1-D) ZnO nanostructure arrays, such as nanowires, nanonails and nanotrees, are synthesized by oxygen assisted thermal evaporation of metallic zinc on a quartz substrate over a large area. The optical and electrical properties of the ZnO nanowire and nanonail arrays and also the applicability of these ZnO 1-D nanoform arrays as gas sensors are investigated.

The actual growth process of ZnO on Si catalyzed by Au is not of real vapor-liquid-solid (VLS) character in most cases. It is found that if the O2 partial pressure during the initial growth stage is too low, a thin layer of SiO2 and big liquid droplets of Zn-rich alloys are formed first on the substrate surface.

The nanostructure and optical properties of two ZnO thin-film samples grown under the same conditions but on different underlying materials (sapphire and GaN) is compared. The X-ray diffraction results shows that the crystalline quality of ZnO on GaN is slightly better than that of ZnO on sapphire.

Photoluminescence and positron annihilation spectroscopy are used to characterize and identify vacancy-type defects produced in ZnO films grown on sapphire by metal-organic chemical-vapor deposition. The found relation between the intensity of the photoluminescence spectra and Zn vacancy concentration indicates that the 370.5nm (3.346 eV) emission line is related to the presence of Zn vacancies.

The optogeometric properties of various sensitive thin films involved in gas sensing applications are investigated by using the m-line technique and atomic force microscopy. Variations of these optical properties are studied under butane and ozone exposure. OCIS codes: 310.2790, 310.6860.

Variable-aspect ratio, (1-D) ZnO nanostructures were prepared and the effect of environmental parameters on the ZnO structure was investigated. The low-temperature syntheses yielded aspect ratios of the 1-D ZnO nanostructures that depended on the water content, the individual ZnO nanorods and nanowires were found to be perfect, single crystals with their c axes as the primary growth direction.

A study is conducted to investigate the structural and photoluminescent (PL) properties of ZnO/Zn(sub 0.8)Mg(sub 0.2)O coaxial nanorod heterostructures using transmission electroscopy (TEM) and temperature-dependent PL spectroscopy. The TEM images show that ZnO/Zn(sub 0.8)Mg(sub 0.2)O layers were epitaxially grown on the entire surfaces of ZnO nanorods and the ZnO nanorod diameters as a core material were as small as 9(plusmn)2 nm.

Pulsed laser deposition technique was used for growing thin films of ZnO on Si(100) substrate held at different temperatures (T(sub s)). All the deposited films showed a preferential c-axis orientation associated with varying grain size as a function of T(sub s) ranging from 100 to 600 degree Celsius.

Optical properties of metal (Al, Ag, Sb and Sn)-ion-implanted ZnO films are studied by ultraviolet-visible spectroscopy and spectroscopic ellipsometric techniques. The effects of metal-ion doping on the optical band gap (E(sub g)), refractive index (n) and extinction coefficient (k) of nanocrystalline ZnO films are studied for the similar implantation dose of all the metal ions.

ZnO thin films were epitaxially deposited on platinum/c-sapphire epitaxiai layer using a radio frequency magnetron sputtering method. ZnO films prepared with Ar showed no electro-optical response however, films prepared with Xe show a linear response of change in the birefringence with the electric field.

Luminescence properties of ZnO films, which are epitaxially grown on c-sapphire (0001) substrates by plasma-assisted molecular beam epitaxy, are investigated by means of different excitation sources and their measurement conditions. With the increase of measurement temperature, photoluminescence spectra clearly present the appearance of different bound-exciton peaks with an abrupt increase of emission intensity at the measurement temperature of 30-50 K.

Manganese-doped zinc oxide (ZnO:Mn) tetropod whiskers were fabricated which were based on vapor-phase transport method. X-ray diffraction and high-resolution transmission electron microscopy demonstrate that the tube pods and the tips are composed of wurtzite ZnO growing along [0001] direction.

The structural design and optimization of ultraviolet (UV) photonic crystal laser based on zinc oxide are presented. A computational supercell technique is developed which allows a straightforward calculation of the photonic band structure of ZnO photonic crystal slab on sapphire substrate.

Stimulated emission was studied using time-integrated and time-resolved photoluminescence in ZnO comb, tetrapod, and rod nanostructures. The nanostructures were fabricated by vapor deposition and hydrothermal methods.

A novel ammonia aqueous solution method for growing well-aligned ZnO nanorod arrays on a silicon substrate is developed. Uniform ZnO nanorods were grown on the zinc-coated silicon substrate in aqueous solution containing zinc nitrate and ammonia water.

An enhancement effect of ultraviolet illumination on the photoluminescence intensities of zinc oxide thin films is reported. It is found that the intensities of excitonic emission and green-band emission increased with ultraviolet light exposure time until a maximum value is achieved.

Zn(sub 1-x)Mg(sub x)O epitaxal thin-film composition spreads by layer-by-layer pulsed laser deposition method where the composition across the chip is linearly varied from ZnO to MgO is fabricated. The ZnO phase appears without precipitation of the MgO phase, which supports the idea of extended substituional solid solution.

Photoluminescence from zinc oxide nanoparticles, nanorods, microparticles, and single crystals is measured under various conditions of ultraviolet excitation. The intensities of both emissions from each zinc oxide sample exhibited a different nonlinear dependence on the excitation density.

The origin of the deep-level emission of ZnO grown by molecular-beam epitaxy using rf plasma for atomic oxygen is investigated. A shift in deep-level emission from green to yellow is observed with reduced Zn pressure during the growth.

The ultrafast lasing dynamics of single zinc oxide (ZnO) nanotetrapods and nanowires are investigated by two-color femtosecond excitation/optical injection spectroscopy. The optical gain spectra obtained as a function of time and wavelength provide a means to distinguish the lasing from other emissions and are thus used to investigate the wavelength-dependent lasing dynamics in nanowires.

A ZnO/SnO2 core-shell heterostructure is used to demonstrate the possibility of establishing a three-dimensional epitaxial interface between two materials with different crystal systems for the first time and show possible tailoring optical properties by building the heteroepitaxial crystal interface. The structural characterizations show that as-prepared ZnO/SnO2 heterostructure exhibits unique luminescence properties in contrast with individual tetrapod ZnO and SnO2 nanostructures, in which the epitaxial interface induces new luminescence properties.

The effect of thermal diffusion of indium in ZnO thin films, prepared using spray pyrolysis technique, and the characterization of ZnO:In films are discussed. The optical and structural studies suggest that good quality ZnO thin films could be developed without affecting crystallinity, optical transmittance, or its photoluminescence emission properties through the simple doping process.