纳米氧化锌的制备

以硫酸锌和碳酸铵为原料,直接沉淀法制得纳米氧化锌的前驱体,然后煅烧得到纳米氧化锌.采用 TG-DTG、XRD和TEM等测试手段对其进行了表征.结果表明,前驱体为Zn4(OH)6CO3.通过控制煅烧温度、反应温度和反应物浓度可以得到不同粒径的球形纳米氧化锌.得出了最佳制备工艺条件.     

High quality amorphous indium zinc oxide thin films synthesized by pulsed laser deposition

Indium zinc oxide films were grown from targets with two different In atomic concentration [In/(In + Zn)] of 40% and 80% by the pulsed laser deposition technique on glass substrates from room temperature up to 100 °C. X-ray diffraction and reflectometry investigations showed that films were amorphous and dense. Thin films (thickness < 100 nm) exhibited higher optical transmittance and resistivities than thick films (thickness > 1000 nm), probably caused by a significant decrease of oxygen vacancies due to atmosphere exposure. Films deposited from the In rich target under an oxygen pressure of 1 Pa exhibited optical transmittance higher than 85%, resistivities around 5- 7 × 10^− 4 Ω cm and mobilities in the 47-54 cm²/V s range.     

Optical and electrical properties of zinc oxide/indium/zinc oxide multilayer structures

Zinc oxide/indium/zinc oxide multilayer structures have been obtained on glass substrates by magnetron sputtering. The effects of indium thickness on optical and electrical properties of the multilayer structures are investigated. Compared to a single zinc oxide layer, the carrier concentration increases from 8 × 10¹⁸ cm⁻³ to 1.8 × 10²⁰ cm⁻³ and Hall mobility decreases from 10 cm²/v s to 2 cm²/v s for the multilayer structure at 8 nm of indium thickness. With the increase of indium thickness, the transmittance decreases and optical band gap shifts to lower energy in multilayer structures. Results are understood based on Schottky theory, interface scattering mechanism and the absorption of indium layer.     

Novel petal-like ZnO crystal synthesized by organic solution method

ZnO crystals with different morphologies have been synthesized by an organic solution method using Zn(CH₃COO)₂ · 2H₂O and polyvinylpyrrolidone as precursors. X-ray powder diffraction, field emission scanning electron microscopy and transition electron microscopy were used to characterize the obtained samples. The results showed that novel petal-like ZnO particles could be obtained when the molar ratio of Zn²⁺/C = O was 1 : 4. The particle had uniform diameter in 200–300 nm and with good dispersibility. Otherwise, octahedron shaped particles with sub-crystalline were achieved when the molar ratio of Zn²⁺ to the carbonyl group of polyvinylpyrrolidone was 1 : 2 or 1 : 8.     

Optical properties of amorphous-like indium zinc oxide and indium gallium zinc oxide thin films

The paper presents the optical properties of amorphous-like indium zinc oxide and indium gallium zinc oxide thin films with various In/(In + Zn) ratios obtained by Pulsed Laser Deposition. Thickness results obtained from simulations of X-ray Reflectivity and Spectroscopic Ellipsometry data were very similar. The dependence of density on stoichiometry resembles the corresponding dependence of the refractive index in the transparency range. A free carrier absorption was noted in the visible spectral range, leading to a weak absorbing thin transparent conductive oxide. On the other hand, the refractive index is smaller than those of based oxides (ZnO and In₂O₃), and counterbalance therefore the weak light absorption.     

Synthesis of nanocrystalline NbAl3 by laser ablation technique

Synthesis of nanocrystalline material has been developed using laser ablation technique. NbAl₃ nanocrystalline powders have been synthesized by laser ablation and identified by transmission electron microscopy (TEM). The average particle size was measured about 5.0 nm. Production yield and ablation rate were obtained as a function of He background pressure and laser pulse energy by measuring the weight of produced powders and weight loss of the target material before and after experiment. The ablation rate appeared to be relatively constant over the range of the He gas pressure. Production rate varied along with both He gas pressure and laser pulse energy. Optimum condition for efficiently high production rate is at 1.0 Torr of He gas pressure and at 320 mJ of the laser pulse energy.     

Composition,morphology characteristics,and optical properties of molybdenum oxide nanostructures synthesized by the laser ablation method in liquid

We present experimental data on composition, morphology, and certain optical properties of nanostructures of molybdenum oxides (MoOx). We show that, upon ablation in water, molybdenum oxides are predominantly synthesized as amorphous masses containing particles (clusters), below 1–2 nm in size, and foam-like structures. We note that the gas bubbles (occurring in the liquid during ablation) might serve as templates for hollow quasi-spherical formations observed in the experiment.     

Secondary emission of nanocrystalline zinc oxide

The Raman and photoluminescence (PL) spectra of nanocrystalline zinc oxide produced by mechanochemical synthesis were measured using a pulsed nitrogen laser (337.1 nm) and xenon lamp (360 nm) as excitation sources in PL measurements and a cw Nd:YAG laser in Raman measurements. PL was observed in the range 400–800 nm. The Raman spectrum of nanocrystalline (90 nm) ZnO was compared to that of coarsegrained ZnO. The Raman bands of nanocrystalline zinc oxide were found to be shifted to lower frequencies and broadened. Laser radiation was shown to cause local heating of zinc oxide up to 1000 K, resulting in photoinduced formation of zinc nanoclusters. Mixtures of zinc oxide and sodium chloride powders are heated to substantially lower temperatures. Under nitrogen laser excitation, the green PL band (535 nm), characteristic of bulk ZnO, is shifted to longer wavelengths by 85 nm. The results are interpreted in terms of light confinement in zinc oxide microclusters consisting of large number of nanocrystallites. The photoinduced processes in question may be a viable approach to producing metal-insulator structures in globular photonic crystals, opals, filled with zinc oxide.     

Optical and electrical properties of aluminum-doped zinc oxide nanoparticles

Aluminum-doped zinc oxide nanopowders were prepared using a surfactant assisted complex sol–gel method, and were characterized using inductively coupled plasma, X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and UV–Vis spectroscopy. Al was effectively doped into the ZnO matrix with concentrations up to 6.00 atomic ratio percents (at.%). X-ray diffraction results revealed that all of the nanoparticles had a pure hexagonal wurtzite structure free of any impurities when annealing temperature was below 1273 K. The optical band gap of the nanopowders, which was affected by the Al-doping concentration, reached a maximum of 3.43 eV when ZnO was doped with 4.00 at.% Al. The effect of post-annealing temperature and vacuum conditions on the resistivities of the Al-doped ZnO nanoparticles was also investigated. And the lowest volume resistivity (1.2 Ω cm) was achieved by annealing the Al-doped ZnO nanoparticles in a vacuum at 1173 K for 2 h.     

Optical and electrical properties of zinc oxide films prepared by spray pyrolysis

Zinc oxide thin films were prepared on glass substrates from an aqueous solution of zinc acetate by spray pyrolysis. These films were characterized using X-ray diffraction, scanning electron microscopy and optical transmission. The films were highly transparent to the visible radiation and electrically conductive. Films deposited at optimum conditions exhibited a resistivity of 3·15×10⁻³ Ωm along with a transmittance of 98% at 550 nm.     

Optical properties of nanocrystalline ceria

We believe that, for the first time, the UV-visible optical reflectivity of nanocrystalline ceria with various particle sizes has been measured, and their optical absorption characteristics have been studied by Kramers-Kronig transformation. The wide absorption band in the 200-480-nm range consisted of two narrow bands. This wide band was designated as the charge transfer of O(2p)-Ce(4f) while both narrow bands, which overlapped in this wide band, were due to the well-known (2)F(5/2)-(2)F(7/2) spin-orbit splitting of the Ce 4f(1) state. With a decrease in the particle sizes of the samples, the bandwidth expanded distinctly and a red shift in the wide band was observed. On the other hand, the band gap between the narrow bands showed a remarkable increase. All of these phenomena resulted from the effects of quantum size and the interface of nanostructured materials.     

ZnO薄膜的电沉积制备及其荧光特性研究

以Zn(NO3)2水溶液为电解液,用阴极电沉积法分别在透明导电玻璃ITO和FTO衬底上制备了ZnO薄膜.X射线衍射(XRD)和扫描电子显微镜(SEM)分析结果表明ZnO薄膜属六角纤锌矿结构,ZnO颗粒均匀,大小约1μm;在室温光致发光谱(PL)中(激发波长为385和390nm)分别观察到了波长位于439和442nm处的较强的蓝光发射峰.本文讨论了样品蓝光峰的发光机理,并指出蓝光峰与样品中由锌填隙引起的潜施主能级上的电子到价带的跃迁有关.     

Optical and electronic properties of cobalt-doped zinc oxide films prepared by the sputtering method

In-doped ZnO, Co-doped ZnO and Li-doped NiO are successively deposited on quartz by the sputtering method. A current versus voltage curve of the three-layer device, in which the Indoped ZnO and Li-doped NiO are used as electrodes, reveals that the In-doped ZnO is an ohmic electrode and the Li-doped NiO is a blocking electrode with respect to electron injection. In photocurrent spectra of the three-layer device, there are two distinct peaks around 410 and 640 nm. The former is ascribed to the photoionization caused by the electric-dipole transition from the ground states,⁴A₂(F), to the conduction band, and the latter to the thermal emission from electronic excited states of Co²⁺,⁴T₁(P).     

激光法制备碳质纳米材料

通过介绍在气体和液体介质中激光与固体材料相互作用的过程,评述了激光在不同介质中发生物理化学现象的差异.与气相中相比,激光冲蚀液体中固体材料产生的气态等离子区受到了液体限制,在该区域会产生更高的气态密度、温度和压力,适合于亚稳相纳米晶的合成.同时评述了激光制备碳基纳米材料的进展.激光在气相和液相中均可制得碳纳米管,气相中适于制备结构完整的碳纳米管,而液相中有利于纳米金刚石的合成.激光冲蚀液体中的石墨靶制备的纳米金刚石粒径较大,辐照石墨悬浮液工艺不仅可以获得超细的纳米金刚石还可以获得线型碳.激光法制备的碳基纳米材料具有尺寸小、纯度高和形状多样性,在未来有着广泛的潜在应用价值.     

Properties of nanocrystalline zinc oxide thin films prepared by thermal decomposition of electrodeposited zinc peroxide

Zinc peroxide thin films were electrodeposited from aqueous solution at room temperature using H₂O₂ as the oxidation agent. Nanocrystalline zinc oxide thin films were then obtained from thermal decomposition of zinc peroxide thin films. The grain sizes of ZnO through thermal decomposition of ZnO₂ at 200 °C, 300 °C and 400 °C were estimated from the peak width of ZnO(110) obtained from X-ray diffraction and were 6.3 nm, 9.1 nm and 12.9 nm, respectively. The optical properties of zinc oxide thin films have been studied. The photoluminescence results indicate that ZnO thin films have low Stokes blue shift (about 110 meV) and low oxygen vacancies.     

Femtosecond laser deposited zinc oxide film and its optical properties

Zinc oxide (ZnO) thin films have been grown on Si (100) substrates using a femto-second pulsed laser deposition (fsPLD) technique. The effects of substrate temperature and laser energy on the structural, surface morphological and optical properties of the films are discussed. The X-ray diffraction results show that the films are highly c-axis oriented when grown at 80 °C and (103)-oriented at 500 °C. In the laser energy range of 1.0 mJ-2.0 mJ, the c-axis orientation increases and the mean grain size decreases for the films deposited at 80 °C. The field emission scanning electron microscopy indicates that the films have a typical hexagonal structure. The optical transmissivity results show that the transmittance increases with the increasing substrate temperature. In addition, the photoluminescence spectra excited with 325 nm light at room temperature are studied. The structural properties of ZnO films grown using nanosecond (KrF) laser are also discussed.     

Blue fluorescence of decorated nano zinc oxide/polystyrene hybrid thin film prepared by pulsed laser ablation

Decorated nano ZnO/PS organic sol was successively produced by pulsed laser ablation at the interface of ZnO ZnO target submerged in the flowing liquid of butyl acetate solution of PS which contained salicylic acid, then decorated nano ZnO/PS hybrid thin film was obtained. It is found that decorated nano ZnO/PS hybrid thin film radiates intense blue light under ultraviolet radiation and has a broad emission band centered at 448 nm in the emission fluorescence spectrum. TEM shows that the size of the nano ZnO particles distributes between 10 nm and 15 nm. TG-DSC reveals that the heat resistance of decorated nano ZnO/PS hybrid thin film increases.     

Optical properties of zinc oxide thin films doped with aluminum and lithium

Aluminum doped Zinc Oxide (AZO) and Lithium doped Zinc Oxide (LZO) thin films are obtained by Pulsed Laser Deposition (PLD) method. These films are characterized by using Spectroscopic Ellipsometry (SE), X-ray Diffraction (XRD) and Photoluminescence (PL). By modeling the ellipsometry spectra we get the dielectric functions, the optical band gap E_g, and the electrical properties. Our results show the influence of the processing parameters on the optical and structural properties of doped ZnO thin films. The post-annealing treatment applied to AZO thin films, changes strongly the optical properties, by lowering the resistivity and red-shifting the band gap.