Optical Spin Injection and Carrier Transport in Hybrid Nanostructures of Semiconductors and Magnetic Metals

本论文的研究目标如下：1.制备由II-VI化合物稀磁半导体和磁性金属组成的量子线、量子点和量子阱的混杂纳米结构。2.研究混杂纳米结构中的光学自旋注入和自旋输运及其在自旋电子器件中的应用。基于上述目标，我们利用分子外延和电子束光刻的方法，分别以CdTe、CdSe、ZnTe、ZUSE和磁性材料Mn、Co为原料制备了量子纳米结构和杂化纳米结构。利用强磁场下的飞秒激光光谱研究了制备的量子结构和杂化纳米结构。研究了双量子阱中的自旋注入过程，其中量子井激子的瞬时光致发光显示了自旋注入和自旋弛豫过程。阐明了自旋超晶格中的自旋转换过程，其中向上和向下的…分布在外加磁场的作用下，ZUTE层和ZMnTe层中更多的激子的n自旋态在空间上分离。由于激子自旋的大塞曼分裂，激子的最低自旋态从ZnTe层修改为ZuMnTe层。根据激子光致发光的瞬时特性，确定了反转自旋注入过程(自旋开关)，并确定了自旋注入时间。利用瞬时泵浦探测光谱研究了这些稀磁纳米结构中激子的超快自旋动力学。在飞秒到纳秒的时间范围内，阐明了高密度电子-空穴等离子体、激子和锰离子中的自旋动力学。利用电子束光刻技术制备了杂化纳米结构。混合结构中的稀磁量子阱受到磁场的影响，磁场是由邻近量子阱的铁磁性钴线感应的。这些现象对于自旋电子的应用具有很高的可能性。较少

The objective of the research is following:1.Fabrication of hybrid nanostrctures of quantum wires, quantum dots and quantum wells, which are composed of II-VI compound diluted magnetic semiconductors and magnetic metals.2.Study of optical spin injection and spin transport in the hybrid nanostructures and application for spin electronic devices. For the above objective, we have fabricated the quantum nanostructures and hybrid nanostructures with CdTe, CdSe, ZnTe, ZuSe and magnetic materials of Mn and Co by using molecular expitaxy and electron beam lithography methods. Fabricated quantum and hybrid nanostructures are studied by femtosecond laser spectroscopy in high magnetic fields. Spin injection processes are investigated in CdTe-CdMnTe double quantum wells, where the transient photoluminescence of quantum-well excitons shows that spin injection and spin relaxation processes. Spin switching processes are clarified in ZnTe-ZnMnTe spin superlattices, where the distribution of up-and dow … More n-spin states of excitons is spatially separated in Zute and ZnMnTe layers by the external magnetic fields. The lowest spin state of excitons is modified from that of the ZnTe layer to that of the ZuMnTe due to the large Zeeman splitting of the exciton spins in the ZnMnTe layer. From the transient characteristics of the exciton photoluminescence, the reverse spin injection process (spin switching) is confirmed and the spin injection times are determined. Ultrafast spin dynamics of excitons is investigated in these diluted magnetic nanostructures by transient pump-probe spectroscopy. The spin dynamics in the high density electron-hole plasma, excitons, and Mn ions are clarified in the femotsecond to nanosecond time region. Fabrication of hybrid nanostructures is made by using electron beam lithography technique. The diluted magnetic quantum wells in the hybrid structures are affected by the magnetic field, which is induced by the ferromagnetic Co wires neighboring to the quantum wells. These phenomena have high possibilities for spin electronic applications. Less