【作者】 刘一星；

【导师】 余亚斌；

【作者基本信息】 湖南大学 ， 凝聚态物理， 2008， 硕士

【摘要】 在纳米体系中,由于尺寸限制将引起尺寸效应,派生出纳米体系具有与宏观体系不同的低维物性。展现出许多不同于宏观材料的物理和化学性质。如纳米体系中能级的不连续性将影响电子在纳米结构中的电输运特性和光学性质变化。本文主要分析在量子点体系中如何产生自旋电流,以及量子限制效应导致的纳米体系发光蓝移现象。纳米结构体系发光蓝移现象一直是近年来大家关心的热点问题。文中分别采用了周期方势垒和周期δ势垒两种简单的一维模型,通过直接严格求解该模型下薛定鄂方程,给出晶场中的限域情况下电子能级结构以及纳米体系中电子的限域能,从而研究体系的发光蓝移现象。基于限域能的计算,讨论了纳米体系的限域能和发光蓝移随尺寸以及势场的变化关系。我们的结果表明:导带底的电子能级随体系的尺寸增大而降低;而价带顶则随粒径的增大而升高大,因此,限域能随纳米尺寸的减小迅速增大。同时将计算结果与通常文献中所采用的有效质量计算的结果进行比较,可以看出二者有明显差别,且尺寸越小,其差异越大。因此,限域能随尺寸的变化并不严格满足通过有效质量方法计算出来的结果。另外文中也分析了限域能与晶场势高度的关系,结果表明限域能随之增大而减小。另外本论文的我们利用量子点体系的输运特性,研究了一种产生自旋极化电流的器件。为了研究通过量子点的自旋电流和极化电流的产生方法,我们采用了一具有三端接口的模型来进行研究,这个模型包括了一个铁磁端口和两个非磁性端口,此三端接口通过量子点弱。更多还原

【Abstract】 As we know, the properties of nanostructure material are very different from these in macroscopic level, because of the size effects. The discrete energy levels in the nanostructure which can influence the electronic transport and optical properties. In this thesis, we report some result on the growth of the pure spin current and the spread of the energy gap in nanostructure.Recently, considerable attention is being paid to the blue-shift of the nanostructure. We study the electronic energy spectra and confinement energies by solving the Schrodinger equation accurately, using two simple model of one-dimensional, under this model. We analyse the band gap blue shift of nanostructure by calculating the confinement energies in nanostructure and discussing the size-confinement energies and potential-confinement energies characteristic curve. The results suggest that the QDs with small size have a higher electron energy at the bottom of the conduction band and lower electron energy at the top of the valence band. So the confinement energies increased abrupt as the size of nano-particle decreased. Meanwhile, the confinement energies which are calculated by the effective mass approximation referred in many literatures are very different from the result we calculate by Schrodinger, when the particle size is small. Moreover, we also find that band gap blue shift depends on the potential in the particle. The confinement energies decreased as the potential increased.Meanwhile, in order to get a generator of spin current, we propose a three terminals spin device, which composed of a ferromagnetic metal lead (source), a semiconductor lead (collector) and a paramagnetic control electrode. Each of the terminals has a bias voltage. For proper tunnel rates and other parameters, the pure spin current can be obtained in one of the terminal, by modulating the controlling voltage.更多还原