有机半导体中电流自旋极化性质研究

【作者】 任俊峰；

【导师】 解士杰；

【作者基本信息】 山东大学 ， 凝聚态物理， 2006， 博士

【摘要】 电子既有电荷又有自旋。以电子电荷为基础的微电子学在二十世纪取得了巨大成功，但是在传统的微电子器件中，电子的自旋却一直被人们忽视，电子只被看成电荷的载体，不同数目的电子或空穴丰富了半导体材料的输运特性。金属自旋阀中巨磁电阻（GMR，giant magnetorcsistance）和隧道磁电阻（TMR，tunneling magnetoresistance）效应的发现引发了磁存储和磁记录领域的革命，并由此产生了围绕电子自旋的控制、输运、测量等的一门全新的学科—自旋电子学（Spintronics）。电子自旋注入和相关的输运过程是当前感兴趣和广泛被研究的课题。自旋注入包括从铁磁金属到超导体；铁磁金属到导体；铁磁金属到非磁性半导体以及磁性半导体到非磁性半导体，或这些构型的复合等。 自旋电子学基于磁学和微电子学，它不但研究电子电荷的输运特性，同时也研究电子自旋在固体材料中的输运特性，以及设计开发基于电子自旋相关效应下工作的器件。自旋电子器件有希望同时利用电子的电荷和自旋来进行信息的传输和存储，这会大大提高现有电子器件的工作速度和效率。利用电子的自旋还可能制备出具有全新物理性能的半导体电子器件，甚至实现量子存储和量子计算。二十世纪九十年代起传统自旋阀已经在计算机中获得了广泛的应用。 与传统的半导体相比，有机半导体的合成要容易得多。有机半导体具有丰富的电学、光学和磁学特性，并且已经在有机发光器件OLED（Organic Light Emitting Diodes）、显示器等方面得到了广泛的应用。由于自旋—轨道相互作用比较弱，有机半导体成为自旋输运的最佳候选材料之一。有机材料中实现自旋极化注入和输运将是自旋电子学的下一个研究热点。2002年，Dediu研究组首次报道了La_0.7Sr_0.3MnO₃/T6/La_0.7Sr_0.3MnO₃三明治结构中的自旋注入和输运。随后2004年，Xiong等人在La_0.7Sr_0.3MnO₃/Al_q3/Co有机自旋阀中开展了自旋注入和输运的重要实验。研究有机半导体内的自旋注入和输运对进一步理解有机材料的物理性质，探讨其在自旋电子学及生命系统中的功能和应用具有重要的科学意义。 有机半导体中自旋注入和输运的理论研究包括以Xie等人为代表的量子理论和以Ruden、Smith以及Yu等人为代表的经典理论两个方面。微观的量子力学研究可理解铁磁/有机系统的微观结构以及自旋输运动力学；从经典的自旋扩散更多还原

【Abstract】 The electron is a quantum mechanical object which, apart from charge, also has aspin. Devices and integrated circuits based on the electronic charges and theirtransportation have been widely used in the world. Electrons and holes enrichment thetransport characters of semiconductor materials. However, the electron is treated asthe carrier of the charge and the spin of the electron usually are neglected. Thediscovery of GMR (giant magnetoresistance) and TMR (tunneling magnetoresistance)in metallic spin valves have revolutionized applications such as magnetic recordingand memory, and launched the new field of spin electronics—’spintronics’, which iscentered on the electron spin including their generation, transport and detection.Electron spin injection and spin dependent transport are essential aspects ofspintronics and have been extensively studied in a number of different contextsincluding: from ferromagnetic metals to superconductors; from ferromagnetic metalsto normal metals; from ferromagnetic metals to nonmagnetic semiconductors andfrom magnetic semiconductors to nonmagnetic semiconductors or the mixture ofthem.Spintronics is based on the magnetics and microelectronics. In the spintronic devices, it is not the electron charge but the electron spin that carries information, and this offers opportunities for a new generation devices using the charge and the spin of electrons together. This device may further enhance the information technology and thus create a new complexation, for example, to incorporate massive storage with information processing, or to inject spin polarized current to control the spin state of carriers. The advantages of the spintronic devices would be nonvolatility, increased data processing speed, decreased electronic power consumption, and increased integration densities. The intrinsic binary nature of electronic spin suggests it could be used as the basic unit, the qubit, for quantum computation and communication. Conventional spin valves have been widely used in computers since the mid 1990s.Compared with conventional semiconductors, organic semiconductors have更多还原