Tm3+/Yb3+共掺氧卤碲酸盐玻璃上转换发光研究

研究了Tm³⁺/Yb³⁺共掺氧卤碲酸盐玻璃的上转换发光光谱，分析了Tm₂O₃含量对Tm³⁺/Yb³⁺共掺氧卤碲酸盐玻璃上转换发光的影响机理.结果表明：在Tm³⁺/Yb³⁺共掺氧卤碲酸盐玻璃的上转换发光中，Tm³⁺存在较强的浓度猝灭效应.随Tm₂O₃含量增加，Tm³⁺的上转换蓝光和红光强度先增加，后降低，在0.1mol% Tm₂O₃达到最大.该结果有助于进一步提高Tm³⁺的上转换发光效率.     

Surface investigation of Si(1 0 0), Cu, Cu on Si(1 0 0), and Au on Cu with positron annihilation induced Auger-electron spectroscopy

The surfaces of polycrystalline Cu, Au-coated Cu, Si(1 0 0) and of Si(1 0 0) coated with 1.5 monolayer Cu were investigated with positron annihilation induced Auger-electron spectroscopy (PAES). Since the electron background has been reduced considerably we observed the Cu M_2,3VV-Auger transition on a copper surface within only three hours which is the shortest acquisition time reported so far for PAES. In order to demonstrate PAES’ high potential the Auger-yield, the signal-to-background ratio as well as the surface selectivity were compared with accompanying EAES-measurements quantitatively. A more efficient electron energy analyzer for the present PAES setup would lead to an additional efficiency gain of more than two orders of magnitude. The presented measurements were performed at the low-energy positron beam of high intensity NEPOMUC at the research reactor FRM II.     

GeS2-Ga2S3-CdS透明表面微晶玻璃的二阶非线性光学效应

采用热诱导法制备了GeS2-Ga2S3-CdS硫系微晶玻璃,X射线衍射(XRD)、透射光谱、扫描电子显微镜(SEM)测试结果表明,获得了含CdGa2S4微晶的透明表面微晶玻璃。采用Maker条纹法研究了微晶玻璃的二次谐波(SHG)效应,结果表明玻璃中的CdGa2S4微晶诱导了二次谐波效应的产生。CdGa2S4微晶在玻璃表面择优生长时,破坏玻璃的各向同性,可获得两个包络的Maker条纹,且入射角在±(35°~50°)左右时,二次谐波的相对强度出现最大值,二阶非线性强度最大可为α-石英单晶的8倍;CdGa2S4微晶在玻璃表面无择优生长时,由于玻璃表面较大的CdGa2S4晶粒的散射作用,只能获得一个包络的Maker条纹,即入射角为0°时,二次谐波的相对强度出现最大值。     

Long lasting phosphorescence of Eu in reduced SrO-B2O3 glasses

The blue long-lasting phosphorescence (LLP) phenomenon was observed for Eu²⁺-doped SrO-B₂O₃ glasses prepared in the reducing atmosphere. The phosphorescence peaks at about 450 nm due to the 4f5d→4f transition of Eu²⁺. With the doping of different amounts of Eu²⁺, the concentration-quenching phenomenon was observed for both the LLP and photoluminescence of the glasses, and the critical concentration for the two cases was same, i.e., 0.02 mol% Eu²⁺. And by the investigation of the TL curves, the content of Eu²⁺ had an effect on the trap depth of the samples. At last the possible mechanism of the LLP of the samples was suggested.     

Electrical characterization of MOS memory devices containing metallic nanoparticles and a high-k control oxide layer

We study the electrical characteristics of a MOS structure in which Pt nanoparticles are embedded. This structure has a tunneling oxide of 3.5 nm in thickness (a SiO₂ thermal oxide layer) on top of a Si wafer, and a control oxide of 27 nm (HfO₂ layer deposited by electron gun evaporation). The nanoparticles are deposited on the SiO₂ layer with electron gun evaporation, at room temperature. The electrical study of the structures demonstrates that the “write” process is initiated at low electric fields. This indicates that this type of memory structure can be very promising for the fabrication of high speed MOSFET memory devices with low power consumption. Our charge retention measurements also show promising results.     

Collision-induced migration of CO on Pt(9 9 7) surface

Lateral displacement of adsorbates induced by collisions with energy-controlled rare gas atoms was examined in an ultra high vacuum chamber using Fourier-transform infrared (FTIR) spectroscopy and a supersonic molecular beam apparatus. A stepped Pt(9 9 7) surface was exposed to CO molecules and subsequently to energy-controlled Ne or Ar atoms. There was no change in the CO stretching mode region of the FTIR spectrum of the Pt(9 9 7) surface after Ne atoms having an average translational energy of 0.23 eV were collided with it. However, when Ne atoms having an average translational energy of 0.56 eV were collided with the surface, the intensity of the peak assigned to the CO stretching mode at terrace sites decreased, while that at step sites increased with increasing the exposure to the Ne atoms. This is the demonstration of collision-induced migration, showing that CO molecules adsorbed at the terrace sites migrate laterally to the step sites upon collision with high-energy Ne atoms. In addition, the experimental results demonstrate the existence of an additional energy barrier for jumps across the steps. This investigation demonstrates an advantage of using a molecular beam for studying adsorbate migration.     

On the theory of thermal density fluctuations in the glassy state: Application to poly(vinyl acetate)

A theory of the liquid state, suitably modified for the glass, contains a characteristic structure functionh, which represents a free volume fraction. As shown previously by means of experimental pressure-volume-temperature studies,h retains finite, nonvanishing temperature and pressure coefficients upon passing through the glass transition. These results are now employed to compute the mean-square thermal density fluctuations in poly(vinyl acetate). AboveT _g , the result attests again to the satisfactory quantitative performance of the equilibrium theory. BelowT _g , two glasses formed at low and elevated pressures, respectively, are considered under quasi-equilibrium conditions. The results show the anticipated initial accord with the approximation proposed by Fischer and Wendorff, involving the isothermal compressibility of the liquid atT _g . The theory delineates the increasing departures with decreasing temperature observed in the literature. We comment finally on the trend of the fluctuations on approaching absolute zero. Explicit low temperature calculations remain to be undertaken.Dedicated to Professor Dr. F. H. Müller.     

Retention behaviour in micro-HPLC on various types of glasses modified with phenyl groups

Summary The retention and selectivity behaviour of some antiepileptic drugs were studied by micro high-performance liquid chromatography on nine types of phenyl-modified glasses, prepared with xylene solution containing phenyldimethylchlorosilane (P), diphenylmethylchlorosilane (D) or triphenylchlorosilane (T), using three types of glass with various mean pore diameters and/or specific surface areas. From elemental analysis data for carbon, the maximum number of accessible phenyl surface groups per 100?² of glass (mean pore diameter: 335?, specific surface area: 69m²/g) in P, D and T gel was calculated to be 2.38, 1.58 and 0.76, respectively. Using various CH₃CN−0.01 M KH₂PO₄ mixtures as eluents, the antiepileptic drugs were separated on all the glasses studied, but with different degrees of resolution. With an increase in the specific surface area, the k′ values of some antiepileptic drugs also increased.     

掺Er3+钆硼硅酸盐玻璃及玻璃陶瓷的红外发光特性和热稳定性

报道了一种新型可作为掺铒光纤放大器(EDFA)基质材料的Er³⁺掺杂B₂O₃-SiO₂-Gd₂O₃-Na₂O(BSGN)体系玻璃及其玻璃陶瓷。对材料中铒的⁴I_13/2→⁴I_15/2跃迁的1.5μm发射光谱、吸收光谱、时间分辨光谱及寿命进行了测量和分析,讨论了热处理对玻璃材料带宽和寿命的影响。结果表明,铒掺杂玻璃1.5μm发射的带宽和J-O参数Ω₆都随B₂O₃含量的增加而增加,寿命随B₂O₃含量的增加而减小。经过热处理后得到的玻璃陶瓷比具有相同组分的玻璃具有更高的1.5μm发射效率。同时,差热分析的数据表明,该玻璃体系具有极好的热稳定性。     

Effects of texture on shear band formation in plane strain tension/compression and bending

In this study, effects of typical texture components observed in rolled aluminum alloy sheets on shear band formation in plane strain tension/compression and bending are systematically studied. The material response is described by a generalized Taylor-type polycrystal model, in which each grain is characterized in terms of an elastic–viscoplastic continuum slip constitutive relation. First, a simple model analysis in which the shear band is assumed to occur in a weaker thin slice of material is performed. From this simple model analysis, two important quantities regarding shear band formation are obtained: i.e. the critical strain at the onset of shear banding and the corresponding orientation of shear band. Second, the shear band development in plane strain tension/compression is analyzed by the finite element method. Predictability of the finite element analysis is compared to that of the simple model analysis. Third, shear band developments in plane strain pure bending of a sheet specimen with the typical textures are studied. Regions near the surfaces in a bent sheet specimen are approximately subjected to plane strain tension or compression. From this viewpoint, the bendability of a sheet specimen may be evaluated, using the knowledge regarding shear band formation in plane strain tension/compression. To confirm this and to encompass overall deformation of a bent sheet specimen, including shear bands, finite element analyses of plane strain pure bending are carried out, and the predicted shear band formation in bent specimens is compared to that in the tension/compression problem. Finally, the present results are compared to previous related studies, and the efficiency of the present method for materials design in future is discussed.