The luminescence of self-activated and copper-doped zinc selenide

The photoluminescence excitation and emission spectra of crystals of zinc selenide doped with copper or chlorine have been measured. The luminescence studies show that crystals doped with chlorine contain a slight trace of copper contaminant. Since the self-activated emission associated with chlorine and the low-energy copper emission overlap in the red region of the spectrum, it is necessary to remove all traces of copper from a crystal to isolate the self-activated emission. This has been done by heating crystals in molten zinc. In this way it has been possible to show that at 85 °K the self-activated emission band lies at 6150 Å, whereas the copper-red emission occurs at 6400 . The self-activated emission is excited strongly in a band centred at 4850 Å, while the copper-red emission is excited in a band centred at 5100 Å. The various transitions Å involved are discussed.     

Edge emission in zinc selenide

Three different series of edge emission bands, associated with donor—acceptor recombination, have been observed at 10 K in crystals of zinc selenide grown in a continuous flow of argon or in sealed capsules in the presence of excess zinc or selenium. It is tentatively suggested that two of these series are associated with random and preferential pairing of the same donors and acceptors.     

Bound-to-bound and bound-to-free yellow emission of ion-implanted zinc telluride

Broad structureless emission bands centred near 580 nm have been observed in the low temperature cathodoluminescence emission spectra of zinc telluride single crystals implanted with zinc, argon or aluminum ions. Time-resolved spectroscopy measurements and measurements of the emission intensities as a function of sample temperature and of temperature of post-implantation isochronal annealing show that one yellow band occurs in both ZnTe : Zn and ZnTe : Ar and results from bound-to-free recombination involving an intrinsic donor level, probably due to a V_Te defect. In addition, there is a second yellow band present in ZnTe : A1 which is due to donor-acceptor pair recombination with the donors and acceptors identified with Al_Zn and V_ZnAl_Zn respectively.     

Aqueous Synthesis of Water-Soluble Citrate-Modified Cadmium Selenide/Cadmium Sulfide/Zinc Sulfide Quantum Dots

Water-soluble cadmium selenide/cadmium sulfide/zinc sulfide core/shell/shell quantum dots were synthesized in aqueous solution using trisodium citrate as modifier. The crystal structure, morphology, component, and spectral properties of cadmium selenide/cadmium sulfide/zinc sulfide core/shell/shell quantum dots were characterized by X-ray power diffraction, transmission electron microscope, energy dispersive X-ray analysis, infrared spectrum, ultraviolet–visible absorption spectrum, and fluorescence spectrum. The results show that the spherical citrate-modified cadmium selenide/cadmium sulfide/zinc sulfide core/shell/shell quantum dots with diameter around 3.6 nm belong to the cubic zinc blende structure. The citrate-modified cadmium selenide/cadmium sulfide/zinc sulfide core/shell/shell quantum dots show a narrow, symmetric, and strong fluorescence emission spectrum band with narrow full width at half maximum of 53 nm, and the fluorescence quantum yield can reach up to 37.3%. The high-quality citrate-modified cadmium selenide/cadmium sulfide/zinc sulfide core/shell/shell quantum dots with good fluorescence properties have potential for application in biological fluorescence analysis.     

Green luminescence in diffusion-doped layers of zinc selenide

Diffusion-doped layers with a green emission band dominating in the room-temperature luminescence spectrum are obtained by annealing single-crystal zinc selenide substrates in tellurium and zinc vapors.     

Synthesis of zinc oxide nanosheet thin films and their improved field emission and photoluminescence properties by annealing processing

ZnO nanosheet thin films have been synthesized through a solvothermal route. These obtained nanosheets disperse quasi-vertically and homogenously on the copper substrates and range in thickness from 80 nm to 250 nm. The as-grown nanosheet thin films were then annealed in the oxygen-presented atmosphere. Field emission plots indicate that the value of turn-on field is reduced from 2.86 V/μm to 1.52 V/μm and the corresponding value of threshold field decreases from 7.19 V/μm to 4.45 V/μm after annealing processing. Room temperature photoluminescence spectrum from the sample annealed at 850 °C in almost pure oxygen atmosphere shows only UV emission and a blue shift while the visible light band is unobservable compared with those of the other two samples, indicating that the crystalline quality of the obtained zinc oxide nanosheet thin films is greatly improved through annealing treatment. This solution approach combined with annealing treatment can, therefore, be regarded as a convenient route to fabricate high-quality crystalline ZnO nanomaterials.     

Comparative analysis of emission and absorption spectra of zinc oxide powders

Photoluminescence and optical absorption spectra induced by proton and electron irradiation in zinc oxide powders have been investigated. It has been found that the emission band in a visible region with a maximum of about 2.3 eV is a superposition of three bands with 2.55, 2.34, 2.12 eV, respectively, caused by oxygen vacancies V _O⁺, interstitial oxygen O _i ⁻, and zinc vacancies V _Zn⁻ absorbing in the 3.03-, 2.83-, and 2.64-eV bands.     

Structure and nonlinear optical properties of zinc selenide films

The linear and nonlinear properties of polycrystalline zinc selenide films are investigated as a function of their deposition conditions. It is shown that the complex nonlinear refractive index correlates with the crystallite dimensions in the deposited film. This correlation suggests the localization of electrons in surface states of the crystallites as a possible mechanism of optical nonlinearity in zinc selenide films excited in the transparency band at a wavelength of 633 nm. Zh. Tekh. Fiz. 67, 60–63 (September 1997)     

Strong ultraviolet emission from zinc oxide thin films prepared by electrophoretic deposition

In this paper, we report a simple and efficient method to prepare high-quality nanocrystalline ZnO films by electrophoretic deposition. Absorption spectrum and transmission electron microscope image indicated that the average size of ZnO nanoparticles is about 9.5 nm. A strong ultraviolet emission peak at 384 nm is observed and the deep-level emission band is barely observed at room temperature. X-ray diffraction pattern revealed that the ZnO film has a polycrystalline hexagonal wurtzite structure. The Raman spectrum showed a typical resonant multi-phonon process within the ZnO film. The frequency shift of 1 LO phonon was about 583 cm⁻¹.     

Synthesis of Cu-ZnO and C-ZnO nanoneedle arrays on zinc foil by low temperature oxidation route: Effect of buffer layers on growth, optical and field emission properties

Different densities of ZnO nanoneedle films have been prepared by pre-coated zinc foils with thin layer of copper and carbon followed by thermal oxidation at 400 °C in air. The X-ray diffraction patterns show well defined peaks, which could be indexed to the wurtzite hexagonal phase of ZnO. The scanning electron microscope images clearly reveal formation of ZnO needles on the entire substrate surface. The X-ray photoelectron spectroscopy studies indicate that Cu and C ions are incorporated into the ZnO lattice. Photoluminescence studies evaluate different emission bands originated from different defect mechanism. From the field emission studies, the threshold field, required to draw emission current density of ∼100 μA/cm², is observed to be 2.25 V/μm and 1.57 V/μm for annealed zinc foil pre-coated with copper and carbon, respectively. The annealed film with copper layer exhibits good emission current stability at the pre-set value of ∼100 μA over a duration of 4 h. The results show that buffer layer is an important factor to control the growth rate, resulting in different density of ZnO needles, which leads to field emission properties. This method may have potential in fabrication of electron sources for high current density applications.     

Ultraviolet emission properties of ZnO film with zinc deficiency by SS CVD

A-b axis orientation ZnO film on silicon (1 0 0) substrate has been prepared by a single source chemical vapor deposition technique. X-ray photoelectron spectroscopy results revealed that the film was very close to stoichiometry but with a small amount of zinc deficiency. Temperature-dependent (10-300 K) ultraviolet photoluminescence of the film was presented. Comparing the photon energy separation of the several groups in the near band edge ultraviolet luminescence bands, as well as the variation of the relative intensities and the shift of the luminescence lines at different temperatures, free-, bound-exciton and its assisted phonon emission were observed, which corresponded to the mechanism of the ultraviolet emission properties. A strong ultraviolet emission resulting from the recombination of free-exciton was observed at 300 K photoluminescence spectrum examined in atmosphere environment. Contrasted to the relatively weak ultraviolet emission of the film in vacuum, atmosphere environment was found to be an important contribution to the strong ultraviolet emission of the film.     

稀土无机发光材料Ca1—nMgnS：Cu^＋,Eu^2＋的合成与光谱特征

报道了Ｃｕ＾＋，Ｅｕ＾２＋共激活的Ｃａ１－ｘＭｇｎＳ的发光性质，基质组分变化与荧光性质的关系，Ｃｕ＾＋和Ｅｕ＾２＋在纯ＣａＳ基质中的发射光谱分别位于４３０ｎｍ及６３０ｎｍ附近，随着基质中Ｍｇ含量的增加，红，蓝区发射峰值波长基本不变，但强度发生明显改变，当ｎ为０．２５时，红区发射强度最强。     

氧化锌纳米线的紫外光耦合增强场电子发射特性

本文采用热化学气相沉积方法制备氧化锌纳米线阵列, 研究氧化锌纳米线阵列在紫外光辐照下的场电子发射特性. 实验结果表明, 在紫外光辐照下, 氧化锌纳米线场发射开启电压降低, 发射电流明显增大. 机理分析认为, 氧化锌纳米线紫外光增强的场发射源自场电子发射与半导体耦合作用, 紫外光激发价带电子跃迁到导带和缺陷能级使发射电子数量增加, 同时, 光生电子发射降低了发射材料表面的有效功函数, 从而显著增强场电子发射性能. 氧化锌纳米线具有紫外光耦合增强场电子发射特性, 在光传感、冷阴极平板显示和场发射电子源等方面具有潜在的应用价值.     

Structural and optical properties of germanium-doped zinc oxide nanorods as a function of annealing temperature

Zinc oxide nanorods with germanium doping were prepared by ion implantation and annealing treatment method, the microstructural and optical properties of which were studied by means of the X-ray diffraction, photoluminescence, and transmission electron microscopy measurements. The pristine sample exhibited a remarkable ultraviolet emission owing to the band edge emission from the zinc oxide matrix, indicated a good crystalline quality. Three emission peaks appeared after germanium ions were doped into zinc oxide nanorods. The 513?nm photoluminescence peak was ascribed to the transition between the vacancy defect in zinc oxide matrix. Photoluminescence peaks located at 548 and 778?nm were ascribed to germanium ions luminescence center in zinc germanate grain and germanium monoxide luminescence center. The light emission tuning was obtained by germanium doping and annealing treatment, which may help the development of the practical optoelectronic devices based on zinc oxide nanomaterials.     

血液静态荧光偏振光谱研究

报道了用408 nm的LED偏振光诱导浓度为0.3%的人全血溶液在350800 nm波段的静态荧光偏振光谱,讨论了其光谱的结构特征和红移现象并给出了机理解释;检测了不同浓度全血溶液荧光偏振光谱中在490nm和610 nm附近处两个各主要荧光区的偏振度,实验结果表明,当血液浓度为1.0%时,在两个主要荧光区的偏振度分别为0.4796和0.4344,当浓度增加到8.0%时,相应的偏拓坟墓分别为0.2064和0.0538。研究了偏振度随浓度的变化规律,用能量转移理论分析了在不同荧光区、不同浓度下,血液中各荧光团之间的不同能量转换机理及偏振度的变化现象。研究结果对光诱导生物组织自体荧光诊断技术有一定的参考价值。     

氧化锌纳米晶体的光谱分析

采用沉淀法并通过控制前驱体的煅烧温度来制备粒径不同的氧化锌(ZnO)纳米晶体,对粒子的透射电镜照片进行分析,结果表明,制备出的纳米粒子分散性好、形貌一致、粒径分布集中。样品的X射线衍射光谱分析表明,随着前驱体煅烧温度增加,晶体粒径增大、结晶度提高;样品的紫外-可见吸收光谱的峰位随粒径减小而发生蓝移,这一实验结果表明ZnO纳米晶体呈现出较明显的量子限域效应;红外吸收光谱测量结果表明,用沉淀法制备的ZnO纳米晶体的表面会吸附一小部分残余的离子,对红外吸收光谱中的ZnO特征振动峰随粒径减小发生宽化和红移的现象进行了理论分析;光致发光光谱测量结果表明,ZnO纳米晶体在紫外区(360 nm)存在一较弱的发光峰,而在可见区(468 nm)存在一较强的发光峰,与理论计算结果进行比较后,认为锌空位点缺陷是导致ZnO纳米晶体可见区发光的主要原因。     

Synthesis of p-type zinc oxide films by plasma-assisted pulsed laser deposition

Heavily acceptor doped zinc oxide (ZnO) films were deposited on quartz substrates by plasma-assisted pulsed laser deposition (PA-PLD) using a non-sintered target heavily doped with phosphorus or copper and radio frequency induction-coupled nitrogen or oxygen plasma (RF-ICP). The p-type ZnO layer was achieved by a nitrogen acceptor dopant using the technique of plasma-assisted nitrogen (PA-N) pulsed laser deposition. Photoluminescence spectra showed a peak from phosphorus- or copper-bound excitons at about 380 nm and a broad, green defect-related band occurring at about 550 nm. Transmission spectra showed a blue shift of the near-band-edge wavelength and a worsening of transmission by heavily copper-doped zinc oxide.     

Thermoluminescence emission spectra and optical bleaching of oligoclase

Thermoluminescence (TL) spectra of oligoclase samples have been recorded in the temperature range from 300 to 700 K and the wavelength range from 300 to 850 nm. Like other feldspars, oligoclase produces blue (peaking at 460 nm) and red (peaking at 765 nm) emission bands. The maximum of the red emission occurs 20 K lower than that of the band. Optical bleaching was performed at wavelengths varying from 360 to 800 nm. Bleaching of artificially irradiated oligoclase causes a decrease of the TL signal. The bleaching efficiency increases with descreasing with wavelegth. Bleaching does not only influence the height of the glow curve but also the shape. An interesting observation is that ratio of the blue and red band intensities is not affected by a bleaching procedure. No evidence has been found that bleaching influences the shape of the emission spectra. The correlation between the blue and red bands is discussed.     

Angle-dependent X-ray emission bands of potassium intercalated graphite

The angular dependent X-ray C K-emission bands of C₈K, C₂₄K and pristine graphite were measured at take-off angles 20° and 80°. For the potassium graphite intercalated compounds (GICs) a pronounced peak is observed at 283.2 eV. Numerical decomposition of the emission bands into their constituent π- and σ-subbands gives evidence for non-rigid band behaviour of potassium GICs and shows that the peak has to be attributed to carbon π-like states.     

Ni2+ emission in SrF2

Luminescence measurements of X-irradiated SrF₂:Ni are reported. After X-irradiation two emission bands have been found. One of them peaked at 293 nm and has an excitation band at 267 nm. The other one at about 770 nm, which is much weaker, has an excitation band at 274 nm. Both emission bands are also observed under X-ray excitation. A comparison with some previous studies of the absorption and thermoluminescence properties of X-irradiated SrF₂:Ni indicates that the emission bands are due to two different kinds of Ni²⁺ centers. The proposed emission mechanisms are similar to those found in CaF₂:Ni.