重金属碲酸盐玻璃中Ho~(3+)的红外辐射特性

制备了高折射率Ho3+单掺和Ho3+/Yb3+共掺低声子能量重金属碲酸盐玻璃.根据Judd-Ofelt理论对吸收光谱进行拟合,求得Ho3+强度参数Ωt(t=2,4,6)分别为4.373×10-20,1.906×10-20和1.451×10-20cm2,并进一步计算了Ho3+在红外区各能级跃迁的振子强度、自发辐射跃迁概率、辐射寿命和荧光分支比等光谱参数.982 nm激发下,铋碲酸盐玻璃中Yb3+直接敏化Ho3+,在红外区产生有效红外发射.Ho3+吸收与发射截面在1.95和2.05μm处分别高达5.63×10-21和6.24×10-21cm2,大于Ho3+掺杂磷酸盐和氟化物玻璃,这有利于降低激光抽运阈值,实现高效Ho3+激光输出.较低的声子能量和较大的发射截面表明,Ho3+/Yb3+共掺杂铋碲酸盐玻璃有望成为良好的红外激光工作物质.     

Eu(TTFA)3掺杂环氧基光刻胶薄膜的强烈红色荧光

合成了稀土配合物Eu(TTFA)3(TTFA, 2-thenoyltrifluoroacetone)掺杂的环氧基紫外负性光刻胶薄膜,采用荧光分光光度计对其光致发光特性进行了系统表征.荧光光谱分析表明,Eu(TTFA)3掺杂的光刻胶薄膜具有很宽的激发谱带(200～400 nm),且在长波紫外区表现为强激发,说明有机配体TTFA-与中心离子之间存在着比电荷迁移带更有效的能量传递.配体TTFA-的三重激发态和Eu3+的激发态能级匹配较好,能很好地敏化Eu3+而发出明亮的红光,是获得Eu3+红色荧光发射的优良配体,认证了有机配体与稀土离子之间产生有效能量传递的前提是存在"天线效应".     

过渡金属掺杂在Bi2Te3体系中诱导产生的磁性

用从头计算方法研究了在Bi₂Te₃体系采用过渡金属掺杂从而诱导出磁性的可能性．用一个过渡金属原子置换一个Bi原子之后,可以在该体系中产生磁矩,这主要是由于过渡金属原子的3d轨道电子的自旋极化导致的．当一个Ti、V、Cr、Mn和Fe原子分别替代一个Bi原子时,体系显示的磁矩分别为0.92、1.97、2.97、4.04和4.98 μ_B．当引入两个过渡金属原子代替两个Bi原子的时候,交换耦合的特性取决于取代Bi原子的分布;代替的Bi原子的位置在Bi1和Bi5的位置时,这两个过渡金属原子之间的距离为11.52 ?, Bi_1.84TM_0.16Te₃体系能量最稳定并且表现出铁磁性耦合．     

Eu(TTFA)3掺杂环氧基光刻胶薄膜的强烈红色荧光

合成了稀土配合物Eu(TTFA)3（TTFA, 2 thenoyltrifluoroacetone）掺杂的环氧基紫外负性光刻胶薄膜,采用荧光分光光度计对其光致发光特性进行了系统表征.荧光光谱分析表明,Eu(TTFA)3掺杂的光刻胶薄膜具有很宽的激发谱带（200 ~ 400 nm）,且在长波紫外区表现为强激发,说明有机配体TTFA-与中心离子之间存在着比电荷迁移带更有效的能量传递.配体TTFA-的三重激发态和Eu3+的激发态能级匹配较好,能很好地敏化Eu3+而发出明亮的红光,是获得Eu3+红色荧光发射的优良配体,认证了有机配体与稀土离子之间产生有效能量传递的前提是存在“天线效应”.     

特殊凸体的p-几何最小表面积

结合p-投影体和p-几何最小表面积的定义,首先,得到了一类凸体p-几何最小表面积的单调性.然后,给出了另外一类凸体p-几何最小表面积的积分表达式,并由此定义了这类凸体的p-混合几何最小表面积,从而得到了一些不等式.     

基于LabVIEW实时研究辐照效应对锰氧化物薄膜电阻的影响

基于LabVIEW编程开发出了一套自动电输运测量系统,并利用该自动测量系统实时测量了γ射线辐照对钙钛矿锰氧化物薄膜La0.67Ca0.33MnO3(LCMO)的电阻率的影响,结果发现LCMO薄膜电阻率在短时间辐照时降低,随着辐射时间增加,电阻率转而单调增加.在同等条件下还测量了1 wt%Nb掺杂SrTiO3(NSTO)的电阻的射线辐射效应,对比发现NSTO的电阻未出现明显变化.通过辐射损伤机理及锰氧化物的强关联电子特征对结果做出了解释.     

Transition Metal Substitutions Induce Ferromagnetism in Bi2Te3

The possibilities of magnetism induced by transition-metal atoms substitution in Bi₂Te₃ system are investigated by ab initio calculations. The calculated results indicate that a transition-metal atom substitution for a Bi atom produces magnetic moments, which are due to the spin-polarization of transition-metal 3d electrons. The values of magnetic moments are 0.92, 1.97, 2.97, 4.04, and 4.98 μ_B for 4% Ti-, V-, Cr-, Mn-, and Fe-doped Bi₂Te₃ respectively. When substituting two transition-metal atoms, the characteristics of exchanging couple depend upon the distributions of the Bi atoms substituted. When two transitionmetal atoms substituting for Bi atoms locate at the sites of Bi1 and Bi5, with the distance of 11.52 Å, the Bi_1.84TM_0.16Te₃ system is energetically most stable and exhibits ferromagnetic coupling.     

Characteristics of ZnO Particles Prepared by Au-catalyzed Phase Transport Technique

ZnO particles were prepared by Au-catalyzed vapor phase transport method on silicon substrate. Scanning electron microscopy(SEM) images show many ZnO particles were formed on the sample surface. They grew up layer by layer along the c-axis, which was confirmed by the results of X-ray diffraction(XRD). The morphology of ZnO particles is close to hemisphere and its formation process could be seen from the SEM image. The room temperature photoluminescence(PL) measurement revealed a narrow UV emission peak at 3.27 eV and a broad green emission peak at 2.45 eV, which was caused by the near-band-edge and deep-level emissions.     

Structural and Optical Properties of ZnO Films with Different Thicknesses Grown on Sapphire by MOCVD

IntroductionZnOis one of the most promising materials for pro-ducing ultraviolet laser at room temperature because ofits wide direct band gap(Eg=3.37eV)and large ex-citonic binding energy of60meV.Recently,much at-tention has been paid to short-wavelength …     

Photoluminescence Properties of Two-dimensional Planar Layer and Three-dimensional Island Layer for ZnO Films Grown Using MOCVD

IntroductionOver the past few years, wide band gap semicon-ductors have attracted considerable attention because oftheir high commercial demand for the preparation ofblue and UV light emitters. The most promising amongall the known materials used for this…