排序方式: 共有86条查询结果,搜索用时 171 毫秒
51.
应用坩埚下降法生长了Pr~(3+)离子掺杂的Na_5Lu_9F_(32)单晶体.系统地研究了Pr~(3+)掺杂的Na_5Lu_9F_(32)单晶的吸收光谱、荧光光谱和荧光衰减曲线.应用Judd-Ofelt理论分析计算了其光学强度等参数,结果表明Pr~(3+)离子处于Pr-F强共价键的高对称环境中.在440nm光的激发下观察到以482、523和605nm为中心的尖锐的强荧光发射带.研究了Pr~(3+)掺杂浓度对上述发光强度的影响规律,实验发现当Pr~(3+)掺杂浓度达到~0.5mol%时,其荧光发射强度达到最大.分析了环境温度从298K到443K变化时对荧光强度的影响,随着温度的增加,荧光强度逐步变弱,且其523nm的绿光受温度影响要小于482nm的蓝光和605nm的红光. 相似文献
52.
53.
High-Rate Growth and Nitrogen Distribution in Homoepitaxial Chemical Vapour Deposited Single-crystal Diamond
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
LI Hong-Dong ZOU Guang-Tian WANG Qi-Liang CHENG Shao-Heng LI Bo Lü Jian-Nan Lü Xian-Yi JIN Zeng-Sun 《中国物理快报》2008,25(5):1803-1806
High rate (〉 50 μm/h) growth of homoepitaxial single-crystal diamond (SCD) is carried out by microwave plasma chemical vapour deposition (MPCVD) with added nitrogen in the reactant gases of methane and hydrogen, using a polyerystalline-CVD-diamond-film-made seed holder. Photolumineseenee results indicate that the nitrogen concentration is spatially inhomogeneous in a large scale, either on the top surface or in the bulk of those as-grown SCDs. The presence of N-distribution is attributed to the facts: (i) a difference in N-incorporation efficiency and (ii) N-diffusion, resulting from the local growth temperatures changed during the high-rate deposition process. In addition, the formed nitrogen-vacancy eentres play a crucial role in N-diffusion through the growing crystal. Based on the N-distribution observed in the as-grown crystals, we propose a simple method to distinguish natural diamonds and man-made CVD SCDs. Finally, the disappearance of void defect on the top surface of SCDs is discussed to be related to a filling-in mechanism. 相似文献
54.
本文描述了一种将区域融熔法与Bridgman方法相结合的单晶生长炉,用它可生长直径为1—1.3cm、长度可达15cm且适用于超声研究用的萘(Naphthalenc)单晶.该晶体生长炉具有结构简单、操作方便以及随时可以观察炉内单晶生长情况等优点.文中讨论了晶体容器的形状对单晶生长的影响,也简单介绍了汽相生长萘单晶薄片的实验.萘是较软的单晶体,所以本文提及的研磨和抛光方法对制备其它软的单晶体(同样适用于声学测量)也许具有参考价值. 相似文献
55.
56.
以高技术电子材料-铁电单晶体为研究对象,在对铁电体中电畸内的细观力学耦合场分析的基础上,采用Mori-Tanaka方法以自洽的方式导出了材料构元的Helmholtz自由能及Gibbs自由能函数的解析表达式。并分析在广义应力空间和广义应变空间中,按Hill-Rice内变量本构理论框架,导出了铁电体畸变屈服面方程,增量型本构关系及内变量的演化方程。文末给出了对BaTiO3单晶材料力电行为的一维数值模拟 相似文献
57.
58.
SUO Kai-Nan ZHANG Wei-Lian LI Jian ZHAO Jia-Peng ZHOU Zi-Peng 《结构化学》2007,26(10):1247-1251
In order to discuss the application possibility of SiGe crystal in thermoelectric materials,we investigated the thermoelectric properties of several silicon-germanium alloys with different content,orientation and electric conductive type. As discussed in the experiment result,the absolute value of Seebeck coefficient fluctuates from 300 to 600 μV/K in the whole temperature range. In the present paper,the relationship of Seebeck coefficient against content,orientation and electric conductive type is summarized in detail. The Seebeck coefficient of the sample with <111> orientation is smaller than that in <100> at the same temperature. Absolute value of P-type is larger than that of N-type except pure Ge. But as the temperature increases,the absolute value of pure Ge decreases many times as quickly as that of other specimens. In addition,the specimens of bulk GeSi alloy crystals for experiment were grown by the Czochralski method through varying the pulling rate during the growing process. 相似文献
59.
60.
晶体取向对单晶体断裂特征影响的模拟分析 总被引:3,自引:0,他引:3
结合Ni基单晶合金制三种不同晶体取各的紧凑拉伸试样试验,本文利用考虑有限变形和晶格转动效应的晶体滑移有限元程序对单晶体三维裂特征进行了模拟计算分析,详细考察了裂纹尖端三维应力场特征和断裂特征,结果表明:晶体取向对裂纹尖端应力场有较大影响,但应力沿试样厚度方向明显分成两个部分,在试样心部,应力沿厚度方向变化不大,在试样外表面则明显变化,裂纹尖端张开位移(CTOD)沿厚度方向类似分成两个部分,垂直于滑 相似文献