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

本研究的目的如下：1。由II-VI化合物稀释磁性半导体和磁性金属组成的量子线、量子点和量子阱混合纳米结构的制备。杂化纳米结构中光学自旋注入和自旋输运的研究及其在自旋电子器件中的应用。为此，我们利用分子探针和电子束光刻技术制备了CdTe、CdSe、ZnTe、ZuSe和磁性材料Mn、Co的量子纳米结构和杂化纳米结构。利用飞秒激光光谱技术研究了高磁场下制备的量子和杂化纳米结构。研究了CdTe-CdMnTe双量子阱中的自旋注入过程，量子阱激子的瞬态光致发光显示了自旋注入和自旋弛豫过程。阐明了ZnTe-ZnMnTe自旋超晶格中的自旋开关过程，其中Zute和ZnMnTe层中激子的n-自旋态在空间上被外磁场分离。由于ZnMnTe层中激子自旋存在较大的塞曼分裂，使得激子的最低自旋态由ZnTe层的最低自旋态改变为ZuMnTe层的最低自旋态。从激子光致发光的瞬态特性出发，确定了自旋注入过程（自旋开关），并确定了自旋注入次数。利用瞬态泵浦-探针光谱研究了这些稀释磁性纳米结构中激子的超快自旋动力学。高密度电子空穴等离子体、激子和锰离子的自旋动力学在飞秒到纳秒的时间范围内得到了澄清。利用电子束光刻技术制备了杂化纳米结构。杂化结构中被稀释的磁量子阱受到磁场的影响，磁场是由量子阱附近的铁磁Co线产生的。这些现象具有很高的自旋电子应用可能性。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