稀土离子Tm3+掺杂Bi2WO6的可见光催化性能

以Na₂WO₄·2H₂O和Bi（NO₃）₃·5H₂O为主要原料,采用水热法合成了稀土离子Tm³⁺掺杂的Bi₂WO₆光催化剂。采用XRD、SEM、TEM、Raman、PL、DRS研究了Tm³⁺掺杂Bi₂WO₆的物相,微观形貌和可见光催化性能。结果表明,Tm³⁺掺杂有效提高了Bi₂WO₆的光催化性能,当掺杂量为6%时,样品的光催化性能最好,可见光照射30 min后,对罗丹明B的降解效率达到91.27%,而可见光照射5 h后,对焦糖色素的降解效率达45.25%。与未掺杂Bi₂WO₆相比,分别提高了27.78%和35.22%。     

Influence of Li dopants on thermoluminescence spectra of CaSO4 doped with Dy or Tm

Thermoluminescence emission spectra are presented for lithium doped variants of CaSO₄:Dy or CaSO₄:Tm dosimetry material. All three dopants (Li, Dy and Tm) variously introduce different changes in both the glow peak temperatures and the luminescence efficiency. In every case the emission signals display the line emission characteristic of the rare earth ions. At temperatures below ∼50 K the relative peak intensities differ for Dy and Tm doped samples, and there are small temperature shifts between the Dy:Li and Tm:Li co-doped materials. Above room temperature the rare earth ions do not show peak temperature movements when co-doped with lithium. However they do influence the peak temperature by ∼5 °C when they are the sole dopant. Inclusion of lithium dramatically moves the high temperature glow peak from ∼200 °C down to 120 °C. All these changes are consistent with a single defect model in which the trapping sites and luminescence occur within the complexes formed of the rare earth ion, an intrinsic sulphate defect and lithium. The evidence and rationale for such a model are presented. There is discussion which suggests that such defect complexes are the norm in thermoluminescence.     

纳米银米表面等离子激元增强上转换发光

上转换纳米发光材料因发光效率普遍较低限制了其在应用领域的进一步发展。利用贵金属的局域表面等离子体共振特性调控发射体的局域场成为提高上转换纳米粒子发光性能的有效途径之一。在这个工作中,我们利用合成工艺简单的贵金属米状结构,通过调控上转换纳米颗粒周围的局域场,实现了上转换发光强度的大幅提高。结合三维有限元方法研究了在实际薄膜中Ag米之间可能出现的不同接触方式对所产生的局域场增强效果的影响,同时证实这种局域等离激元耦合所引起的电磁场增强是提高上转换发光性能的重要因素,并且获得了上转换发光将近百倍的增强效果。最后,通过调控等离子层和发光层的厚度,实现上转换发光性能的进一步优化。     

四能级和准四能级激活离子的最佳掺杂浓度

推导了在连续抽运和脉冲抽运条件下,利用荧光衰减曲线,在双掺与单掺晶体中,激发态布居数与激活离子掺杂浓度的关系,分析了四能级系统与准四能级系统中激活离子最佳掺杂浓度的计算方法.并利用上述方法,以准四能级系统Tm,Tb:LiYF4和四能级系统Nd:YAG为例,计算了相应离子的最佳掺杂浓度,并与文献的有关报道进行了比较 关键词： 激发态布居数 最佳掺杂浓度 四能级系统与准四能级系统 Tm Tb:LiYF4     

Cr，Tm∶YAG晶体中的能量转移

通过对Ｃｒ∶ＹＡＧ、Ｔｍ∶ＹＡＧ和Ｃｒ，Ｔｍ∶ＹＡＧ晶体吸收光谱和发射光谱的比较，研究了Ｃｒ，Ｔｍ∶ＹＡＧ晶体中的能量转移过程．指出Ｃｒ３＋→Ｔｍ３＋能量转移过程中，无辐射能量转移占绝对优势．     

Luminescent CdSe and CdSe/CdS core-shell nanocrystals synthesized via a combination of solvothermal and two-phase thermal routes

A new solvothermal route has been developed for synthesizing the size-controlled CdSe nanocrystals with relatively narrow size distribution, and the photoluminescence (PL) quantum yields (QYs) of the nanocrystals can reach 5-10%. Then the obtained CdSe nanocrystals served as cores to prepare the core/shell CdSe/CdS nanocrystals via a two-phase thermal approach, which exhibited much higher PL QYs (up to 18-40%) than the CdSe core nanocrystals. The nanocrystal samples were characterized by ultraviolet-visible (UV-vis) absorption spectra, PL spectra, wide-angle X-ray diffraction (WAXD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM).     

Nondestructive topographic evaluation of ion implanted layers on GaAs substrates by optical absorption

It is demonstrated that ion implanted layers can be analysed prior to annealing by measuring the sub-bandgap optical absorption of the damaged lattice. The absolute value and lateral homogeneity of the implantation dose can be measured. The method is fast, nondestructive and compares favorably with existing measurement techniques.     

激光二极管抽运（Tm，Ho）：YLF微片激光器的实验研究

从理论上分析了准三能级(Tm，Ho)：YLF晶体的增益与温度关系，晶体温度的降低和长度的缩短有利于减小重吸收损耗对激光器运行性能的影响。在室温条件下，用2．7w波长为792nm激光二极管端面抽运Tm(原子数分数0．06)，Ho(原子数分数0．004．)：YLF微片激光器，阈值抽运功率为450W，当入射到晶体内的激光二极管功率为1．88W时，2μm激光最大输出功率为328mW，斜率效率为22．5％，光—光转换效率达17．4％。为达到激光最佳运行条件，还探讨了激光二极管波长，抽运光偏振方向以及晶体温度对Tm，Ho激光器性能的影响。     

Front and back surface cw CO2-laser annealing of arsenic ion-implanted silicon

The annealing behavior of arsenic-implanted silicon under scanned cw CO₂-laser irradiation from front and back surfaces is investigated. Ellipsometry, Hall effect, Rutherford backscattering measurements and neutron activation analysis indicate an enhancement of annealing efficiency by laser irradiation from the back surface, which provides complete recovery of crystal damage, high substitutionality and electrical activation of implanted arsenic atoms without redistribution of concentration profile. The enhancement of annealing efficiency under back-surface irradiation is explained by the difference in laser reflection from the front and back surface of silicon wafers. No differences in the results are found for scanned and static annealing.     

A≈160区奇质量数Tm同位素的能级结构

利用粒子–三轴转子模型,计算了A≈160区奇质量数Tm同位素系列的能级结构.通过调整能隙和科氏减弱因子,较好地拟合了各Tm同位素的低激发转动带,并给出它们的能隙随中子数变化的规律.