Photoluminescence and excitation spectra of the SrO:Bi3+ phosphor

The details of the photoluminescence and excitation spectra are obtained at various temperatures between 6 and 300 K. At low temperatures, the emission band originating from the ³A_1u(sp) → ¹A_1g(s²) transition in a Bi³⁺ ion shows vibrational structure. In the excitation spectra, the A- and C-bands are observed at 365 and about 250 nm, respectively.     

Photoluminescence characteristics of ZnTiO3: Bi nanocrystals

The photoluminescence properties of the Bi³⁺ in sol-gel derived ZnTiO₃ nanocrystals have been investigated. An ultra-violet emission at 360 nm and a visible emission band at 506 nm have been observed, originating from two kinds of emission centers. The former is ascribed to the ³P₁-¹S₀ transition of Bi³⁺ and the latter to the recombination of the electrons with the photo-generated holes trapped in the zinc vacancies. In all cases the latter contribution is predominant.     

Photoluminescence in GdVO4:Bi3+, Eu3+ red phosphor

The doubly doped (Bi³⁺ and Eu³⁺) GdVO₄ powder is synthesized by hydrolyzed colloid reaction (HCR) technique and formation of material is confirmed by XRD measurement. Surface morphology has been studied by SEM measurement and the result shows uniform surface morphology. The average particle size observed by SEM is about 1 7m. The Fritsch particle sizer is used to study the particle size distribution. It distributes from O.15 to 3.57 7m. The small particle size (less than 5 7m) and the narrow particle size distribution, are the necessary requirements of good phosphor material. Photoluminescence result shows a narrow emission line of Eu³⁺ ion (4 nm FWHM) at 618 nm. The Eu³⁺ emission intensity is enhanced by a factor of five with the addition of small amount of Bi³⁺. The emission bands of VO₄^3- and Bi³⁺ partially overlap with the excitation band of Eu³⁺. The process of energy transfer from Bi³⁺ to Eu³⁺ is discussed here. The energy transfer probability is strongly dependent upon the Bi³⁺ and Eu³⁺ concentrations, with a maximum for 0.2 mol % of Bi³⁺ and 3 mol % of Eu³⁺. It drastically decreases for higher concentrations. For photoluminescent applications, the quantum efficiency (QE) of a phosphor material is an important parameter. The QE of GdVO₄:Bi,Eu(0.2,3) is 76%. The GdVO₄:Bi,Eu(0.2,3) material is proposed as an efficient photoluminescent phosphor.     

Photoluminescence of Lu3Al5O12:Bi and Y3Al5O12:Bi single crystalline films

Single crystalline films of Lu₃Al₅O₁₂:Bi and Y₃Al₅O₁₂:Bi have been studied at 4.2–450 K by the time-resolved luminescence spectroscopy method. Their emission spectrum consists of two types of bands with strongly different characteristics. The ultraviolet band consists of two components, arising from the electronic transitions which correspond to the ³P₁ → ¹S₀ and ³P₀ → ¹S₀ transitions in a free Bi³⁺ ion. At T < 80 K, mainly the lower-energy component with the decay time ～10^?3 s is observed, arising from the metastable ³P₀ level. At T > 150 K, the higher-energy component prevails, arising from the thermally populated emitting ³P₁ level. The visible emission spectrum consists of two dominant strongly overlapped broad bands with large Stokes shifts. At 4.2 K, their decay times are ～10^?5 s and ～10^?4 s and decrease with increasing temperature. Both of the visible emission bands are assumed to be of an exciton origin. The lower-energy band is ascribed to an exciton, localized near a single Bi³⁺ ion. The higher-energy band, showing a stronger intensity dependence on the Bi³⁺ content, is assumed to arise from an exciton, localized near a dimer Bi³⁺ center. The structure of the corresponding excited states is considered, and the processes, taking place in these states, are discussed.     

Photoluminescence characteristics of energy transfer between Er and Bi in Gd2O3: Er, Bi

The phosphors, Bi³⁺- activated Gd₂O₃:Er³⁺, were prepared by sol-gel combustion method, and their photoluminescent properties were investigated under ultraviolet light excitation. The emission spectrum exhibited sharp peaks at about 520, 535, 545, 550 and 559 nm due to (²H_11/2, ⁴S_3/2)→⁴I_15/2 transitions of Er³⁺ ions. The luminescent intensity was remarkably improved by the incorporation of Bi³⁺ ions under 340 nm light excitation, which suggested very efficient energy transfer from Bi³⁺ ions to Er³⁺ions. The introducing of Bi³⁺ ions broadened the excitation band of the phosphor, of which a new strong peak occurred ranging from 320 to 360 nm due to the 6s²→6s6p transition of Bi³⁺ ions. There is significant energy overlap between the emission band of Bi³⁺ ions and the excitation band of Er³⁺ ions. Under 340 nm light excitation, Bi³⁺ absorbed most of the energy and transferred it to Er³⁺. The energy transfer probability from Bi³⁺ to Er³⁺ is strongly dependent on the Bi³⁺ ion concentration. Also, the sensitization effectiveness was studied and discussed in this paper.     

Photoluminescence lifetimes of the In,Tl and Bi bound excitons in silicon

We report measurements of the photoluminescence decay times of bound excitons associated with the donor Bi and the acceptors In and Tl in silicon. These are the first reported results for Tl and Bi, respectively the deepest simple acceptor and donor in silicon. The Tl bound exciton lifetime is found to be in good agreement with a value extrapolated from the results for shallower acceptors. The Bi bound exciton, on the other hand, has a much shorter lifetine than an extrapolation from the shallower donor results would predict.     

Photoluminescence characteristics and energy transfer between Bi3+ and Eu3+ in Gd2O3: Eu3+, Bi3+ nanophosphors

Bi³⁺ and Eu³⁺ codoped cubic Gd₂O₃ nanocrystals were prepared by the Pechini sol-gel method. Their photoluminescent properties were investigated under ultraviolet light excitation. The introduction of Bi³⁺ ions broadened the excitation band of Eu³⁺ emission, of which a new strong band occurred ranging from 320 to 380 nm due to the 6s²→6s6p transition of Bi³⁺ ions, implying a very efficient energy transfer from Bi³⁺ ions to Eu³⁺ ions. Upon 325 and 355 nm light excitation, the luminescent intensity of Eu³⁺ ions was remarkably improved by the incorporation of Bi³⁺ ions. But a significant quenching of Eu³⁺ emission was observed under 266 nm light excitation when Bi³⁺ was codoped. The possible energy transfer processes between Bi³⁺ and Eu³⁺ were discussed. The decay curves of Eu³⁺ emission under the excitation of 266 nm pulsed laser were measured and gave further evidence for our discussion.     

Bi80+辐射复合过程的计算

基于Dirac-Slater自洽场方法,计算了Bi79+离子从低能到高能的光电离截面以及其逆过程Bi80+的辐射复合截面; 分析了Kramers公式的适用性;考察了多极效应、相对论效应在不同能区对辐射复合截面的影响;计算了Bi80+离子在电离阈值附近的辐射复合截面和辐射复合速率系数,考察了自由电子分布函数及电子的温度变化对速率系数的影响,并将计算结果同高精度的储存环合并束实验进行了对比.     

Photoluminescence detection of impurities introduced in silicon by dry etching processes

We report on a photoluminescence study of silicon samples subjected to different dry etching processes. Several luminescence lines, known from defects produced by high-energy irradiation, manifest damage of the crystalline material. Noble gas ion beam etching (using Ne⁺, Ar⁺, Kr⁺, and Xe⁺) with ion energies as low as 400 eV produces characteristic luminescence lines which correspond to defects within a 200–300 Å thick surface layer. Incorporation of carbon during CF₄ reactive ion etching produces the familiar G-line defect. The G-line photoluminescence intensity in our samples is directly correlated with the substitutional carbon concentration, as determined by infrared absorption measurements before the etch process; we therefore suggest that a simple method to determine the substitutional carbon concentration in a crystalline silicon sample is a standard dry etching process and a comparison of the resulting G-line photoluminescence intensity to a calibrated sample. The sensitivity of this method seems to be better than 10¹⁴ carbon atoms/cm³.     

Photoluminescence and excited state structure in Bi3+-doped Y2SiO5 single crystalline films

Single crystalline films of Bi-doped Y₂SiO₅ are studied at 4.2–350 K by the time-resolved luminescence methods under excitation in the 3.8–6.2 eV energy range. Ultraviolet luminescence of Y₂SiO₅:Bi (≈3.6 eV) is shown to arise from the radiative decay of the metastable and radiative minima of the triplet relaxed excited state (RES) of Bi³⁺ centers which are related to the ³P₀ and ³P₁ levels of a free Bi³⁺ ion, respectively. The lowest-energy excitation band of this emission, located at ≈4.5 eV, is assigned to the ¹S₀ → ³P₁ transitions of a free Bi³⁺ ion. The phenomenological model is proposed to describe the excited-state dynamics of Bi³⁺ centers in Y₂SiO₅:Bi, and parameters of the triplet RES are determined.     

Synthesis and near-infrared luminescence properties of LaOCl:Nd3+/Yb3+

Near-infrared emitting phosphors LaOCl:Nd³⁺/Yb³⁺ were prepared by the solid-state method, and their structures and luminescent properties were investigated by using X-ray diffraction and photoluminescence analysis, respectively. The studies shows that tetragonal LaOCl:Nd³⁺/Yb³⁺ can be synthesized by the solid-state reaction at 600 °C for 3 h. Upon 353 nm UV excitation, LaOCl:Nd³⁺/Yb³⁺ sample shows strong near-infrared emission lines in the region of 1060–1150 nm (corresponding to ⁴F_3/2 → ⁴I_J′ transition of Nd³⁺, J′ = 9/2, 11/2, 13/2, 15/2) and 980–1050 nm (corresponding to ²F_5/2 → ²F_7/2 transition of Yb³⁺). The decreasing emission intensity of Nd³⁺ with increasing doping concentration of Yb³⁺ proved the energy transfer in LaOCl:Nd³⁺/Yb³⁺. The possible near-infrared emission and energy transfer mechanism between Nd³⁺ and Yb³⁺, as well as the energy transfer efficiency of LaOCl:Nd³⁺/Yb³⁺ were discussed.     

Photoluminescence and electrical properties of Eu-doped (Na0.5Bi0.5)TiO3 ferroelectric single crystals

Eu³⁺-doped Na_0.5Bi_0.5TiO₃ (Eu:NBT) single crystals were grown by a top-seeded solution growth method. Photoluminescence emission and excitation spectra of Eu:NBT were investigated. The two transitions in ⁷F₀ → ⁵D₀ excitation spectra reveal that Eu³⁺ ions were incorporated into two adjacent crystallographic sites in NBT, i.e., Bi³⁺ and Na⁺ sites. The former has a symmetrical surrounding, while the later has a disordered environment, which was confirmed by decay curve measurements. The dielectric dispersion behavior was depressed and the piezoelectric and ferroelectric properties were improved after Eu doping.     

Photoluminescence and energy transfer processes in rare earth ion doped oxide thin films with substrate heating

Tm-Er codoped amorphous aluminum oxide thin films were prepared by pulsed laser deposition. Broadband photoluminescence in the wavelength region of 1400-1700 nm comprised of two emissions at around 1532 and 1620 nm was observed. PL performance was investigated as a function of the substrate-heating temperature. Possible energy transfer processes involved in the heat treatment were discussed and nonradiative decay rates were evaluated, by comparing the inverse of measured lifetimes with the calculated radiative decay rates. Our results suggest that Tm-Er codoped Al₂O₃ thin film might be potential candidate as broadband light sources and amplifiers.     

粉末LaOCl:Eu3+的5D1能级的无辐射跃迁几率

本文使用多次漫反射法测得粉末LaOCl:Eu的漫反射吸收谱,结合所测的LaOCl:Eu的激发光谱,直接得出5D1能级的无辐射量子效率,再由所测5D1能级寿命得出它的无辐射跃迁几率。另一方面,使用Ω参数法,即利用Ω参数计算5D1的辐射跃迁几率,然后由所测寿命值计算出无辐射跃迁几率,来验证第一种方法所得结果。两者结果接近,表明前一种方法是简便可行的。     

Isomeric transitions in203Bi and205Bi

High spin states in^{203, 205}Bi, populated in the^{203, 205}Tl (α,4n) reactions, have been studied using gamma-ray and conversion-electron spectroscopy. Several previously unobserved isomeric transitions were identified by electron-electron coincidence measurements in both isotopes and in²⁰⁵Bi a new isomer was found. The observed states can be explained as arising from couplings of the oddh _9/2 proton to neutron states in the neighbouring Pb cores. Reduced transition probabilities are derived and discussed.     

Photoluminescence of InP:Zn

Photoluminescence spectra of diffusion layers of zinc-doped indium phosphide were investigated. A study was made of diffusion layers obtained in different regimes. A diffusion process was conducted for 30 and 60 min at temperatures of 450–500°C. The photoluminescence spectra consisted of bands with E₁=1.145 eV, E₂=1.37 eV, E₃=1.345 eV, E₄=1.15 eV. Photoluminescence was measured at 77 K upon excitation by laser radiation at 0.44 μm. An analysis is made of the regularities of the change in the spectral dependences for samples with different prehistories by using layer-by-layer etching as well as of the change in the integral Zn activation energy for different temperatures of postdiffusion annealing. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 125–128, January–February, 1997.     

Photoluminescence in heavily doped Si: B and Si: As

We report the results of low-temperature photoluminescence measurements on a series of heavily-doped Si: As and Si: B samples. New spectra are obtained for very high doping levels (10¹⁹ 2- 10²⁰ cm^-3), and the results for the more lightly doped samples are found to be in good agreement with previously published data. By comparing the luminescence of a Si: As sample before and after partial compensation with B, we verify that minority carriers can be localized even in “metallic” samples.