掺镧PbWO4闪烁晶体的缺陷研究

利用正电子湮没寿命谱(PAT)和X射线电子能谱(XPS)研究了掺镧所引起的PbWO₄ 晶体缺陷的变化.结果表明：掺镧后,PbWO₄晶体中的正电子捕获中心铅空位(V< sub>Pb)浓度增加,并进一步诱导低价氧浓度的增加.讨论了掺La的作用机制,认为掺 La将抑制晶体中的氧空位,增加铅空位浓度. 关键词： 掺镧钨酸铅晶体 正电子湮没寿命谱 X射线电子能谱 缺陷     

Gd掺杂的Bi系2212相单晶电子状态的X射线光电子能谱研究

利用X射线光电子能谱(XPS)研究了Bi系纯2212相超导单晶和Gd掺杂的2212相绝缘体单晶的电子状态的区别。实验结果表明Gd掺杂引起超导电性的变化是由于D_2p轨道空穴填充引起。本文还对Cu2p_3/2XPS卫星峰与主峰强度之比(I_s/I_m),Bi-O层性质以及Bi系Fermi能级附近态密度的来源等问题进行了讨论。 关键词：     

γ射线辐照诱导Bi:α-BaB2O4单晶近红外宽带发光的研究

用提拉法技术生长出了掺Bi的α-BaB₂O₄单晶并经过γ射线辐照.测定了样品在室温下的吸收光谱、发射光谱及荧光衰减曲线.在808 nm波长光的激发下,经γ射线辐照后的α-BaB₂O₄单晶中发现了中心波长为1139 nm、半高宽为113 nm的近红外宽带发光现象.讨论了辐照条件和退火处理对Bi离子发光的影响.对于其发光机理进行了初步的探讨. 关键词： 近红外宽带发光 2O₄单晶')" href="#">α-BaB₂O₄单晶 辐照 退火处理     

电子束辐照诱导Bi:α-BaB2O4 单晶近红外宽带发光的研究

用提拉法技术生长出了Bi:α-BaB₂O₄单晶,并进行电子束辐照.测定了电子束辐照前后的吸收谱和荧光发射谱.在808 nm波长激光二极管的激发下,电子束辐照后的Bi:α-BaB₂O₄单晶中观测到了中心波长在1135 nm附近、半高宽为52 nm左右的近红外宽带发光现象.近红外宽带发光的发光中心是Bi⁺离子.电子束射线起到了将Bi³⁺和Bi²⁺还原至一价态 关键词： 近红外宽带发光 2O₄单晶')" href="#">α-BaB₂O₄单晶 电子束辐照     

Mn/GaAs(100)界面的形成和化学反应的研究

利用低能电子衍射(LEED)、X射线光电子能谱(XPS)、电子能量损失谱(EELS)、紫外光电子能谱(UPS),对室温下Mn在GaAs(100)4×1表面的淀积过程进行了研究。研究结果表明,当锰的覆盖度θ≥0.25nm时,LEED图案完全消失,表明Mn没有生长成单晶。LEED,EELS的结果都表明淀积初期是层状生长的。对XPS的Ga2p_3/2,As2p_3/2的峰形、强度进行分析,可以知道在很小的覆盖度下,Mn就与衬底反应。置换出的Ga被局限在离原来的界面约3nm 关键词：     

La1－xPrxMnO3(x=0.1，0.2)薄膜庞磁电阻性质的研究

一种新的庞磁电阻氧化物薄膜La_1-xPr_xMnO₃(x=0.1，0 .2)薄膜用脉冲激光沉积(PLD)方法生长在(100)SrTiO₃单晶基底上.XRD结果显示 薄膜具有很好的外延单晶取向.电输运和磁性质的研究表明薄膜具有显著的庞磁电阻效应(CM R)效应，其中磁电阻比率达95％(在5T的磁场下).X射线光电子能谱(XPS)的结果表明薄膜体 系中Pr离子的价态为+4价，因此该薄膜很可能是电子掺杂的庞磁电阻体系. 关键词： 脉冲激光沉积 1-xPr_xMnO₃')" href="#">La_1-xPr_xMnO₃ 电子 掺杂 庞磁电阻     

Bi2Sr2CaCu2-xSnxO8+δ系列 超导体的XRD和XPS研究

实验研究了Bi₂Sr₂CaCu_2-xSn_xO_8+δ 的X射线衍射(XRD)和光电子能谱(XPS).实验发现随着掺杂(Sn)量的增加,晶格参数a 和c都有所变化,O1s和Cu2p芯能级谱也发生了变化.实验结果表明： 在低掺杂量时,Sn主要 呈二价态;而在高掺杂浓度时呈四价态;掺Sn对超导电性的影响与其他元素的掺杂不同.这 些实验结果支持化学环境在高温超导样品的电子结构中起着重要作用的结论. 关键词： Bi系超导体 掺杂 X射线衍射 光电子能谱     

Tm3+掺杂CdWO4单晶的发光特性

用坩埚下降法生长获得了尺寸为φ25 mm×90 mm、Tm₂O₃初始掺杂摩尔分数为0.5%的CdWO₄单晶。晶体的颜色由上部血红色逐渐加深至下部的黑褐色。对不同部位的晶体薄片进行800 ℃的氧化处理,测定了处理前后不同部位的吸收光谱和FTIR红外光谱。经氧气退火处理后,由于氧空位缺陷减少,晶体的颜色明显变淡。在吸收光谱中观测到421,684,805 nm的吸收带。其中421 nm的吸收峰随退火温度的升高而逐步减弱,经800 ℃处理后基本消失。在808 nm激光二极管激发下,观察到中心波长为1.5 μm和1.8 μm的荧光发射,分别对应于Tm³⁺的³H₄→³F₄,³F₄→³H₆的能级跃迁。     

单晶Si表面离子束溅射沉积Co纳米薄膜的研究

采用离子束溅射沉积法，在单晶Si基片上制备了不同厚度(1—100nm)的Co纳米薄膜.利用原子力显微镜、X射线光电子能谱(XPS)仪和X射线衍射仪对不同厚度的Co纳米薄膜进行了分析和研究.结果表明：当薄膜厚度为1—10nm时，沉积颗粒形态随薄膜厚度增加将由二维生长的细长胞状过渡到多个颗粒聚集成的球状.当膜厚大于10nm时，小颗粒球聚集成大颗粒球，颗粒球呈现三维生长状态.表面粗糙度随膜厚的增加呈现先增加后减小的趋势，在膜厚为3nm时出现极值.XPS全程宽扫描和窄扫描显示：薄膜表面的元素成分为Co，化学态分别 关键词： 离子束沉积 纳米薄膜 X射线光电子能谱 X射线衍射     

P2S5/NH4OH处理GaAs(100)表面的电子能谱研究

采用俄歇电子能谱(AES)和X射线光电子能谱(XPS)研究了P₂S₅/NH₄OH钝化液处理的GaAs(100)表面的微观特性。AES测量表明,在钝化膜和GaAs衬底之间的界面处无O组分,只有P和S组分。XPS测量分析指出,经过P₂S₅/NH₄OH溶液处理后,GaAs表面处Ga₂O₃和As₂O_{3关键词：}     

Thermoactivated spectroscopy of heterovalent impurity traps in CdWO4

Abstract

Recombination luminescence emission spectra, TSL and trap spectra estimated by fractional glow technique (FGT), in nominally pure and Li-, Bi- and Ho-doped CdWO₄, crystals are reported. According to the investigations by FGT heterovalent impurities Li, Bi and Ho causes localized electronic states which act as traps for charge carriers. It is shown that TSL results in emission of known blue-green luminescence band by emptying of the Li⁺-related traps in CdWO₄-Li and yellow luminescence band by emptying of the Bi³⁺-related traps in CdWO₄-Bi. It is proposed that blue-green and yellow luminescence occur by recombination correspondingly of free holes and free electrons at different intrinsic tungstate group related luminescence centers.     

γ射线辐照与O2退火对Bi∶CdWO4单晶体光谱性能的影响

用500和800℃,在氧气下,对掺Bi钨酸镉晶体进行热退火处理,测定了处理后晶体的吸收光谱与发射光谱。随退火处理温度的升高晶体的吸收强度降低,吸收边带发生蓝移。在373与980nm的光激发下,分别观察到发光中心为528nm的CdWO4晶体本征发光与发光中心为1 078nm的Bi 5+发光。晶体样品通过高温氧气处理,发光中心为528nm的荧光带强度增强,但发光中心为1 078nm的荧光带强度变弱。这可能是由于氧退火使Bi 5+转化成Bi 3+所致。经退火处理后,晶体的颜色逐渐变浅,透光率明显提高,这是由于晶体中氧空位减少所致。经γ射线辐照处理后,528nm处的发光增强,而1 078nm处的发光减弱,这可能是由于γ射线辐照后导致Bi 5+变成Bi 3+。     

Fluorescence properties of divalent and trivalent europium ions in CdWO4 single crystals grown by Bridgman method

Optical absorption, excitation, and fluorescence were investigated in Eu ion-doped CdWO₄ single crystal grown by a modified Bridgman method. The results indicate that Eu²⁺ and Eu³⁺ ions coexist in CdWO₄ crystal and an energy transfer occurs between these Eu²⁺ and Eu³⁺ ions. When the crystal is excited by 266-nm light, the energy corresponding to the 4f⁶5d to ⁸S_7/2 transition of Eu²⁺ ions results in the excitation of the Eu³⁺ ions to the ⁵D_J level. The effect on fluorescence of annealing in oxygen at various temperatures was investigated. The excitation intensity of Eu²⁺ ions at 266 nm decreases as annealing temperature increases from 300 K to 1073 K, but it remains at a certain equilibrium level when the annealing temperature is further increased.     

Polarized spectral analysis of Er3+ ions in biaxial Bi2(MoO4)3 crystal

An Er³⁺:Bi₂(MoO₄)₃ single crystal has been grown by the Czochralski technique. The Stark sublevels of the ⁴I_15/2 and ⁴I_13/2 multiplets of Er³⁺ ions in the crystal were determined. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curve of the crystal were measured at room temperature and the relevant spectroscopic parameters, including the Judd–Ofelt intensity parameters, spontaneous emission probability, fluorescence branching ratio, radiative lifetime, and stimulated emission cross section, were estimated. The effect of re-absorption on the spectroscopic parameters was discussed. When the crystal was excited at 977 nm, up-conversion green fluorescence was observed and discussed.     

Luminescence characteristics of Eu3+ activated borate phosphor for white light emitting diode

In this paper, the Sr₃Y₂ (BO₃)₄:Eu³⁺ phosphor was synthesized by high temperature solid-state reaction method and the luminescence characteristics were investigated. The emission spectrum exhibits one strong red emission at 613nm corresponding to the electric dipole ⁵D₀--⁷F₂ transition of Eu³⁺ under 365nm excitation, this is because Eu³⁺ substituted for Y³⁺ occupied the non-centrosymmetric position in the crystal structure of Sr₃Y₂ (BO₃)₄. The excitation spectrum indicates that the phosphor can be effectively excited by ultraviolet (254nm, 365nm and 400nm) and blue (470nm) light. The effect of Eu³⁺ concentration on the red emission of Sr₃Y₂ (BO₃)₄:Eu³⁺ was measured, the result shows that the emission intensities increase with increasing Eu³⁺ concentration, then decrease. The Commission Internationale del'Eclairage chromaticity (x, y) of Sr₃Y₂(BO₃)₄:Eu³⁺ phosphor is (0.640,0.355) at 15 mol% Eu³⁺.     

Spectral properties and emission efficiencies of GdVO4 phosphors

GdVO₄ with activators Eu, Dy, Sm and Bi has been synthesised by a solid-state reaction. GdVO₄:Eu³⁺ (3%) yielded the highest quantum efficiency of 95%. Interesting energy-transfer properties have been revealed in the mixed-activator phosphor (GdVO₄:Eu³⁺, Sm³⁺) when excited in the 4f shell of Sm³⁺ at 408 nm. Bismuth-activated GdVO₄ gives rise to a broad-band emission peaking at 525 nm in comparison to YVO₄:Bi³⁺, which gives an emission peak at 570 nm under UV excitation. The quantum efficiency of GdVO₄:Bi³⁺ increases gradually with bismuth concentration and reaches a maximum of 80% for a bismuth concentration of ≈0.5%. There is a shift in the excitation band of GdVO₄:Bi³⁺ towards longer wavelengths with increasing concentration of bismuth, which can lead to energy transfer from bismuth to europium in a phosphor with both these activators. Heat treatment of GdVO₄:Bi³⁺ at 1500 °C for 3–3.5 h resulted in a large percentage of bismuth being lost from the lattice as evaluated by X-ray fluorescence. However, if a large percentage of bismuth (of the order of 3% or more) is initially added, a sufficient quantity of bismuth can still be retained after heat treatment, which can lead to the development of ceramic scintillators for X-ray tomographic applications. Addition of 3–5% boron gives a white GdVO₄ phosphor without any chemical treatment. Received: 27 Feruary 2001 / Accepted: 1 August 2001 / Published online: 30 October 2001     

Luminescence of ZnWO4 and CdWO4 thin films prepared by spray pyrolysis

Thin films of ZnWO₄ and CdWO₄ were prepared by spray pyrolysis and the structural, optical, and luminescence properties were investigated. Both ZnWO₄ and CdWO₄ thin films showed a broad blue-green emission band. The broad band of ZnWO₄ films was centered at 495 nm (2.51 eV) consisted of three bands at 444 nm (2.80 eV), 495 nm (2.51 eV) and 540 nm (2.30 eV). The broad band of CdWO₄ films at 495 nm (2.51 eV) could be decomposed to three bands at 444 nm (2.80 eV), 495 nm (2.51 eV) and 545 nm (2.28 eV). These results are consistent with emission from the WO₆⁶⁻ molecular complex. The luminance and efficiency for ZnWO₄ film at 5 kV and 57 μA/cm² were 48 cd/m² and 0.22 lm/w, respectively, and for CdWO₄ film the values were 420 cd/m² and 1.9 lm/w.     

铈离子掺杂浓度对氯化镧(LaCl_3:Ce)闪烁晶体发光性能的影响

本文采用垂直Bridgman法,分别生长了未掺杂LaCl3和掺有不同浓度CeCl3的LaCl3闪烁晶体,并对它们的透光性质、发光性质和光衰减特性进行了测试和对比分析.发现未掺杂LaCl3晶体的吸收边位于215 nm附近,本征发射峰为405 nm,衰减时间在1μs以上.该发光属于纯氯化镧晶体的自陷激子发射,但随着CeCl3掺杂浓度的提高,源于自陷激子(STE)的本征发射强度逐渐降低,LaCl3:Ce晶体中的吸收边逐渐红移至300nm,由Ce3+中心所产生的5d→4f发射逐渐增强,其衰减时间加快至～20 ns.这种现象被解释为LaCl3晶格中的自陷激子向Ce3+离子发光中心的能量传递作用所致.     

Luminescence spectroscopy of Ln-doped Bi-containing phosphates and molybdates

The photoluminescence (PL) emission and excitation spectra of undoped and doped with rare-earth (RE = Eu, Tb) ions K₃Bi₅(PO₄)₆ and K₂Bi(PO₄)(MoO₄) crystals are studied in 3.7–14 eV region of the excitation photon energies at T = 8 and 300 K. The mechanisms of the host-related and RE-related luminescence in 3.7–7 eV region of the excitation photon energies are revealed in comparative analysis of the PL spectra of studied compounds. It is assumed that the excitation mechanisms of host luminescence of K₃Bi₅(PO₄)₆ and K₂Bi(PO₄) (MoO₄) crystals below 4.8 eV are related to Bi³⁺ ions in oxygen surrounding. An efficient energy transfer from the Bi³⁺-related luminescence centers to the emitting RE centers exists in crystals with low concentration of the RE dopants (1%). The PL excitation spectra of K₃Bi₅(PO₄)₆ crystals with high concentration of Eu dopants are formed by O – Eu CT transitions.