排序方式: 共有44条查询结果,搜索用时 62 毫秒
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Luminescence intensity of CdS:Mn/ZnS core-shell quantum dots (QDs) can be strongly enhanced in comparison with bulk CdS:Mn and nanoparticles, while the luminescence due to the surface state is greatly suppressed by a capping ZnS shell We find that with the increasing temperature, the peak position of CdS:Mn/ZnS core-shell QDs blue shifts due to the reduction of phonon coupling. Unlike the bulk CdS:Mn, the luminescence of the core-shell QDs is less sensitive to thermal quenching. 相似文献
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A theoretical investigation on the structural and elastic properties of ZnO nanotubes is carried out by using atomistic calculations based on an inter-atomic pair potential within the shell-model approach. The calculation results are presented for the bond length, bond angle, radius dilation, strain energy, Young modulus and Poisson ratio as a function of tube radius. For small tube radius these properties depend on the helicity of the tube, while for the tube radius larger than 6.0A, they are independent of the tube radius and helicity except for the strain energy which decreases with increasing tube radius. 相似文献
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This paper computes the conductance of an open ellipse cavity and discusses the effect of finite leads on conductance. The lead introduces mode coupling with bound states in the cavity which contributes to Fano resonant line shapes in conductance. By examining the resonant states in the cavity, the effects of state mixing and annular probability distribution of wave function due to the presence of leads are found. The results have been compared with the transport properties of other systems. The finite leads result in two effects, i.e. the evanescent mode contribution and additional oscillations, to the conductance.[第一段] 相似文献
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研究了激光推进中铝制旋转抛物面型推力器的温度变化情况。采用脉冲TEA-CO2激光器作为推进光源,用响应较快的K型热电偶丝作为温度传感器,分别在大气呼吸和烧蚀两种工作模式下,研究了抛物面上不同点的温度分布情况,以及脉冲个数和环境气压对抛物面温度的影响。文中对冲量耦合系数和气压的关系也作了研究,并将其与温度联系起来。结果发现在旋转抛物面的顶点处温度为最高,随离顶点距离的增大而减小。在大气呼吸和烧蚀两种模式下,抛物面温度随着激光脉冲个数增加,但增加的斜率逐渐减小,有饱和的趋势。在激光脉冲个数确定的条件下,大气呼吸模式的温度随气压的减小先增大后减小,出现一个峰值;烧蚀模式则随气压的减小而增大。在大气呼吸模式下,冲量耦合系数随着气压的减小先略为增大而后迅速减小,在约0.5atm处出现了一个弱峰;在烧蚀模式下,冲量耦合系数随气压减小迅速升高,在气压低于0.5atm后,几乎为定值。 相似文献
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我们用固相反应法合成了LaBa2Cu3-xZnxOy(0≤x≤1.0)系列样品.X-光衍射分析显示,在整个掺杂区内皆为正交结构,晶格常数a,b和c随掺杂量的增加略有增大.Zn含量的增加使体系正常态的电阻率上升.红外光谱(IR)表明:对于不掺杂的样品,在531cm-1和583cm-1附近有两个显著的吸收峰,随掺杂量x的增加前者基本不移动,后者则向高频移动,强度略有减小.电子顺磁共振实验(EPR)揭示了Zn掺杂对Cu2 的自旋关联行为的影响.本文讨论了掺杂对结构、输运性质和自旋关联的影响. 相似文献
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我们成功合成了LaBa2Cu3-xFexOy(0≤x≤2.0)系列单相样品.X-光衍射分析显示,在x<2.0的整个掺杂区内样品皆保持为正交结构.晶格常数a,b和c随掺杂量的增加而增大.红外光谱(IR)表明:对于不掺杂的样品,在531cm-1和583cm-1附近有两个显著的吸收峰,分别相应于Cu(1)-O和Cu(2)-O的伸缩振动.在低掺杂区 (0≤x≤0.5),535cm-1峰随x增加向低频方向移动,当x>0.5时,该声子振动模随x增加反而逐渐硬化.585cm-1处的红外峰在0≤x≤1.0范围内峰位基本不变.高Fe掺杂区(x>1.0),体系的结构畸变很强,使上述两个红外峰宽化而变成一个宽峰.电子顺磁共振实验(EPR)揭示了不同含量的Fe掺杂对Cu2+的自旋关联行为的影响.本文对不同掺杂区的声子振动,晶格结构和自旋特征进行了分析讨论. 相似文献
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The nucleation kinetics in the early stage of epitaxial growth mediated by a monolayer of surfactant is studied by using kinetic Monte Carlo simulations. Our simulation model includes three main kinetic parameters: a small barrier for adatom diffusion on the surfactant terrace, a higher barrier for the exchange of adatoms with their underneath surfactant atoms, and a highest barrier for the recovery exchange in which an exchanged adatom resurfaces to the top of the surfactant layer. The simulations reveal a distinct transition of nucleation behaviour as the different atomic processes are activated successively with increasing temperature. The total nucleus density as a function of temperature exhibits a complex N-shape with a minimum and a maximum, which define the transition temperatures. The characteristic behaviour of nucleation density is helpful to rationalize the experimental observations on the temperature dependence of growth mode in some surfactant-mediated epitaxial systems. 相似文献
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