量子“囚徒困境”

J.Eisert,M.Wilkens和M.Lewenstein量子化了经典博弈论中的一个著名的例子－－囚徒困境（Prisoners‘ Dilemma）。在他们提出的物理模型中,如果两名博弈参与者采用纯量子策略,就能避免“困境”的出现,并且在该量子模型中,两名参与者的收益值都高于经典模型中的收益值。     

金刚石膜微结构的慢正电子束测量研究

The microstructure of diamond films was studied by slow positron beam and Raman spectroscopy. For the Raman spectroscopy experiment on diamond films, a high fraction of the sp3 hybridized bond was detected in samples. Positron annihilation spectra analysis further illuminated that the concentration and types of defects were different in each sample. S-E curves of all samples showed that diamond crystal structures had obvious variation in each sample. These results indicated that positron annihilation spectroscopy was an effective means to measure microstructure of diamond films.     

Vacancy in 6H—Silicon Carbide Studied by Slow Positron Beam

The defect changes in 6H-SiC after annealing and 10MeV electron irradiation have been studied by using a variable-energy positron beam.It was found that after annealing,the defect concentration in n-type 6H-SiC decreased due to recombination with interstitials.When the sample was annealed at 1400℃ for 30 min in vacuum,a 20-nm thickness Si layer was found on the top of the SiC substrate,this is a direct proof of the Si atoms diffusing to surface when annealed at high temperature stages.After 10MeV electron irradiation,for n-type 6H-SiC,the S parameter increased from 0.4739 to 0.4822,and the relative positron-trapping rate was about 27.878 times of the origin sample,this shows that there are some defects created in n-type 6H-SiC.For p-type 6H-SiC,it is very unclear,this may be because of the opposite charge of vacancy defects.     

金属的正电子双多普勒展宽谱研究

研制了一套数字化的正电子湮没双多普勒展宽谱测量系统,用它测量了10个样品的双多普勒展宽谱,得到了一些有意义的结果.这些结果展示了一些金属单质材料的双多普勒展宽谱随着电子结构变化而发生的变化.本文简略介绍了双多普勒展宽谱仪,实验数据处理,以及这些金属单质材料的数据和分析结果.     

单晶固体中正电子波函数的计算

介绍了正电子波函数计算的两种基本方法——有限差分方法(FDM)与平面波方法(PW).并以单晶Si为例,计算出正电子的波函数,从而计算出正电子在Si中的密度分布,由该正电子密度,进一步计算出了正电子在Si中的体寿命.计算结果与我们最近的实验结果(220 ps)符合得很好.最后,探讨了这两种方法各自的优缺点.     

正电子寿命-动量关联技术

评述了国际正电子领域的新探测技术———寿命 动量关联技术.介绍了该技术的发展过程,讨论了该技术的分析方法,详细阐述了该技术在Ps形成和热化过程中的应用,并讨论了该技术在Ps化学上的应用.A new detection technique--age momentum correlation in international positron field is reviewed. The recent development is described and the analysis methods are discussed for the technique. The application of the technique in the positronium formation and thermalization processes are systematically summarized. Besides the application of the technique in Ps chemistry is discussed.     

Al/GaSb异质结的慢正电子研究

用单能慢正电子束和 X 射线衍射方法研究了 Al/n-GaSb 金属半导体异质结在不同温度退火的情况下的演变.采用三层模型既 Al/界面/GaSb 对 S-E 实验数据进行拟合.结果发现在未退火样品的 Al 和 GaSb 之间存在一个厚度大约5nm 的界面层.在经过400℃退火后,该界面厚度增加到约400nm,且 S 参数下降.这可能是由于在退火过程中,界面区域的原子在界面处相互扩散所引起的.Al 膜的 S_(Al)参数降低且效扩散长度 L_(Al)增加,说明 Al 膜内的空位缺陷经过退火被消除且进行结构重整,晶格结构不断变好的结果.衬底 GaSb 的 S_B 参数和有效扩散长度 L_B 的演变表明,经过250℃退火后,原有的正电子捕获中心消失：但是经进一步400℃退火,又产生了新的正电子捕获中心.这可能来源于其他类型的与 V_(Ga)相关缺陷的正电子捕获以及 Ga_(Sb)晶格反位引起的正电子浅捕获.X 射线衔射的测量结果证实了正电子方法的结论.