利用离子激发发光研究低温条件下ZnO发光行为EI北大核心CSCD

离子激发发光(Ions beam induced luminescence,IBIL)可以实时原位分析不同温度、不同离子辐照条件下材料内部点缺陷的演变行为。本文利用2 MeV H^(+)研究了300,200,100 K温度下ZnO单晶内部点缺陷发光及其随注量的演变行为。实验中发现ZnO深能级发射和近带边发射,结合Voigt分峰与XPS实验结果,确定红光(1.75 eV)与V_(Zn)相关,橙红光(1.95 eV)来自Zn_(i)到O_(i)跃迁;对于与V_(O)相关的绿光(2.10 eV),其红移可能由于温度降低导致更多电子由导带释放到Zn_(i)。峰中心位于3.10 eV和3.20 eV近带边发射分别来自于Zn_(i)到价带的跃迁和激子复合,红移原因分别为Zn_(i)附近局域化能级和带隙收缩。利用单指数公式对发光强度进行拟合,获得的衰减速率常数(f)可以表征缺陷的辐射硬度,对比发现深能级发射峰在200 K时辐射硬度最大,而近带边发射峰在300 K时辐射硬度最大。     

Luminescence and spectroscopy

The connection between luminescence and different chapters of spectroscopy is discussed. Modern theoretical concepts and experimental techniques wiped away the boundaries that traditionally existed between them. Nevertheless, the basic notions of luminescence remain valid. Being focused on the dynamics and kinetics of electronically excited states, luminescence serves as an effective tool in solving numerous problems in contemporary solid-state physics. Electron–phonon interaction, excitons in disordered systems, the emission spectroscopy of the fractional quantum Hall effect and spin injection are discussed as specific examples.     

Luminescence of poly-N-epoxypropylcarbazole

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 53, No. 1, pp. 41–49, July, 1990.     

Luminescence and Reversible Luminescence Thermochromism of Bulk and Microcrystals of Dibenzoylmethanatoboron Difluoride

Essential differences in the luminescence properties of dibenzoylmethanatoboron difluoride (1) bulk and microcrystals were detected. Analysis of the spectral data showed that in every case the fluorescence spectrum of 1 consisted of three components: monomer fluorescence, excimer fluorescence, and fluorescence related with interdimer interaction. Evolution of luminescence spectra observed with decrease of the crystal size are bound with decrease of monomer fluorescence intensity and considerable growth of intensity of fluorescence related to interdimer interaction. The presence of reversible luminescence thermochromism was discovered for 1: lowering the temperature from 300 to 77 K resulted in essential hypsochromic shift of the luminescence band maximum (∼60 nm) connected with considerable decrease of the distances between the planes of the neighboring molecules (∼0.1 Å) that lead to the weakening of interdimer interaction and intensification of monomer luminescence.     

Luminescence of Leuco-Thiazine Dyes

Details of the novel luminescence of the leuco forms of the thiazine dyes, methylene blue and thionine, are reported, including their emission maxima, quantum yields and lifetimes of the luminescence. Other work shows that this luminescence is independent of reducing agent type and solution pH and is a common feature of most thiazine dyes.     

Luminescence of silver chlorides

It was found that single crystals of silver chloride without admixtures, prepared in the Institute of Physics of Charles University, exhibit a luminescent colour change at the temperature of liquid air. According to the change in luminescence the crystals can be divided into three groups —those with predominant red-orange, green-blue and blue-green luminescence.This paper briefly describes the factors influencing the colour changes in the luminescence of silver chloride. More details on the experiments and the connection between the changes in luminescence and the absorption will be given later.In conclusion the author thanks R. Kiradjieffová for her great help in the work.     

闪烁晶体的发光研究进展

概述了近年来闪烁体发光研究的进展,主要介绍用于未来高能物理实验的新型闪烁体发光机理研究,选取我们在研BaF₂,BaF₂:RE,CeF₃以及PbWO₄中的一些新进展。重点谈及三点:(1)在BaF₂的“价带^→芯带”跃迁发光研究基础上进行稀土(Gd³⁺-Eu³⁺)掺杂时观察到的量子剪裁以及对多光子发光的新思考;(2)CeF₃晶体发光的级联能量传递中,Ce³⁺(290nm发射带)与缺陷发光中心(340nm发射带)间能量传递及其传递效率的温度依赖;(3)PbWO₄晶体的发光中心研究中,提出以“WO₄^-2+O_i”绿光中心替代“WO³+F”中心观点的依据。同时也简介了医用闪烁体的最新进展。     

Luminescence of acetylated cellulose

Several luminescence properties of acetylated cellulose were studied as functions of the ester group concentration and of the wavelength of the exciting radiation. Of the three luminescence bands arising on irradiation at specific wavelengths, the ultraviolet band has a structure. A correlation was established between the intensity of this band and the ester group content, as well as a qualitative similarity between the luminescence excitation spectra and the absorption spectra. The relative quantum yield of the luminescence depends on the wavelength of the excited radiation. It is proposed that the centers which are specific for the ultraviolet luminescence are acetyl groups of two different types.     

Luminescence of yttrium oxide

Pulsed cathodoluminescence of pure and neodymium-activated Y₂O₃ ceramic and materials used for its synthesis (commercial Y₂O₃ micropowder and nanopowder obtained from it by laser evaporation) is investigated in a wavelength range of 350–850 nm. In the micropowder, four series of narrow electron-vibration bands of intrinsic luminescence centers are detected. In a ceramic with the same lattice, only one series is left, while the remaining series degenerate into broad bands. In the neodymium-activated ceramic, luminescence bands of the Na³⁺ ion located in the monoclinic lattice of the γ-Y₂O₃ phase are detected.     

局域化电子态集体的荧光

载流子局域化对固体材料的光电性质有着深刻的影响。长期以来，人们就发现许多固体材料的发光异常行为与固体中电子态的局域化密切相关．文章介绍了作者最近所发展的一个局域态荧光模型．借助于一个新推导出来的局域化电子态的分布函数，文章作者发展出了该模型．该模型不但定量地解释了局域态集体荧光的温度依赖的异常现象，而且清晰地揭示了异常现象背后的载流子热动力学物理．文章还介绍了该模型在一些材料的荧光数据分析中的应用。     

Luminescence of copper nanoparticles

Copper nanoparticles have been prepared through the chemical reduction of cuprous ions by ethanol. Freshly prepared colloidal solution shows an absorption band at about 296 nm. The particle size using Scherrer's equation is calculated to be about 12 nm. TEM showed nearly uniform distribution of the particles with an average size of 11 nm. Photoluminescence spectra of copper nanoparticles have also been analysed, which show an emission peak at 530 nm when illuminated at 350 nm. Electroluminescence spectra also give maximum emission at 550 nm.     

Luminescence in amorphous semiconductors

A review of the luminescence properties of amorphous semiconductors is presented. The materials covered are chalcogenide glasses, silicon and arsenic. Luminescence spectra, excitation spectra, temperature dependences and lifetimes are described.

The radiative transition in chalcogenides is the recombination of an electron in the conduction band tail and a trapped hole. A strong electron-phonon coupling distorts the lattice near the trapped hole, lowering its energy. This interaction is responsible for the broadness of the luminescence band and its position at about half the band gap energy. The recombination centre is thought to be a charged dangling bond with density 10¹⁷ cm^-3 in arsenic chalcogenides and 10¹⁶ cm^-3 in selenium. The same centre is observed in the hole drift mobility, and thermally stimulated conductivity.

Luminescence in amorphous silicon also originates from recombination between the band tails and deep centres, with three separate transitions identified. In contrast to chalcogenides the electron-phonon coupling is not strong. The shape and intensity of the spectra are very sensitive to sample preparation and treatment, and correlate with other electrical and optical properties of Si.     

Luminescence of neodymium-doped yttria

Pulsed cathodoluminescence of Nd³⁺: Y₂O₃ nanopowders of the cubic and monoclinic phases and the ceramics synthesized from these nanopowders has been investigated in the spectral range 350–850 nm. It is found that the IR emission band of neodymium ions in the Nd³⁺: Y₂O₃ cubic phase is located at λ₁ ≈ 825 nm. When there is a monoclinic phase admixture, two additional luminescence bands of Nd³⁺ arise in the spectrum at λ₂ ≈ 750 nm and λ₃ ≈ 720 nm. The emission spectrum of all Nd³⁺: Y₂O₃ materials also contains a wide intrinsic band of yttrium oxide at λ ≈ 485 nm; however, the presence of neodymium decreases the intensity of this band and increases the its structurization. It is suggested that the structure of this band in Nd³⁺: Y₂O₃ materials is mainly determined by local absorption (self-absorption) of neodymium ions.