【作者】 陶嘉伟；

【导师】 陈玺；

【作者基本信息】 上海大学 ， 无线电物理， 2011， 硕士

【摘要】 石墨烯(graphene)中电子输运的奇异性质自2004年首次实验上实现单层石墨烯以来受到了的广泛关注,成为当前凝聚态物理的一个研究热点。基于单层石墨烯中Klein隧穿等现象,人们对单层石墨烯构成的单势垒、双势垒以及多层势垒(超晶格)结构中电子的透射,电导以及噪声等展开了深入研究。不仅如此,人们也相继发现了石墨烯的一些电子输运特性与已知的光学性质的相似性,通过这些类比可以进一步研究石墨烯中电子的类光学性质及其调制。本论文将从石墨烯单势垒基本结构中电子传输性质出发,深入研究石墨烯中的一些类光学现象,比如反常空间位移、多层势垒结构中对位移的调制等,这些问题的深入研究不仅极大地丰富了受限小量子系统中电子输运特性研究的内容,而且可以为电子束空间调制器、电子波导开关和自旋电子分束器等量子电子器件和自旋电子器件提供新的原理,为该位移在纳米电子学和自旋电子学等中的应用开辟一个较为广阔的领域。本论文研究内容主要包括以下几部分:1、介绍自石墨烯被首次成功制备后至今的发展历史,以及国内和国外对石墨烯的研究现状及其广泛的应用前景,并介绍石墨烯中奇特电子性质和类光学现象的研究进展等。2、研究石墨烯单势垒结构中电子的输运特性及其能带调制。从电子的Klein隧穿和经典运动出发,研究单层石墨烯势垒结构中电子透射和反射的行为,分析石墨烯中电子束在量子结构中的传输与电子束入射角、入射能量等参数之间的关系,揭示石墨烯量子结构中电子传播的基本性质。研究表明当入射角不为零是,由于Klein隧穿和经典运动的性质,透射率出现能量带隙,相对应的反射率则会出现Bragg带隙,以此构成了完整的理论体系,极大地丰富了单层石墨烯结构中电子透射和反射的特性研究。3、根据已知的单层石墨烯中实现可调控带隙这一研究结果,研究更为一般的单层石墨烯势垒结构,即势垒中具有可调带隙的单层石墨烯结构,其中的电子输运满足有质量的Dirac方程。根据单层石墨烯势垒结构中电子透射率的性质,运用稳态相位法,先后分别研究石墨烯量子结构中在行波场和消逝场两类情况下电子的Goos-H(a|¨)nchen位移特性,研究表明在行波场下,电子处于经典运动时单层石墨烯势垒中的Goos-H(a|¨)nchen为正,而当电子处于Klein隧穿时,GH位移为负,这一性质与光束穿过左手材料介质板的性质完全一致。此外,还研究了单层石墨烯势垒中,Goos-H(a|¨)nchen位移随势垒高度和势垒中石墨烯本征带隙的调制,通过外场调制势垒高度及掺杂改变本征带隙将有助于实现单层石墨烯势垒中GH位移的正负调制。4、研究含势阱的多势垒结构中电子透射带隙以及电导等输运特性。根据已有的研究结果,石墨烯多层势垒中电子传输除了Bragg禁带外,还有一本征带隙,类似于左手和右手材料组成的多层结构中平均折射率为零的带隙,在此基础上研究了含势阱的非对称多层势垒结构中电子的透射率。研究表明,通过量子势阱的调制,本征带隙中出现透射峰,该透射带隙中的共振峰将有利于调节电导等电子输运特性。更多还原

【Abstract】 Graphene has been a hotspot for its particular property since it has been found in 2004. Based on the interesting property, e.g. Klein tunneling, etc, the research in transmission, conductance in monolayer graphene structure, like single barrier, double barriers and superlattice, has been researched comprehensively. In addition, electron transport properties in graphene and the similar optical properties, further study of these graphene analogies to the electron optical properties of the class and its modulation.This dissertation will be discussed from electron transport properties of the basic structure in graphene, then to elaborate optical-like phenomena in graphene, such as GH shift, the modulation on superlattice. These GHL shifts, which can also be modulated by the height of potential barrier and the induced gap, have potential applications in various graphene-based electronic devices. We further hope that these similar phenomena in graphene nanostructure with magnetic-electric barrier and spin-orbit coupling may lead to the graphene based spintronic devices.The main contents include the following aspects:1. Introduce the history from the first time that graphene has been found, and the current situation in the field domestic and overseas. Moreover, introduce the progress in particular electric transmission properties and optical-like research.2. Explain the electric transmission property in singer barrier in monolayer graphene and its modulation. It has been investigated that the transmission in monolayer graphene barrier at nonzero angle of incidence. Taking the influence of parallel wave vector into account, the transmission as the function of incidence energy has a gap due to the evanescent waves in two cases of Klein tunneling and classical motion.3. It has been investigated that the lateral shifts of Dirac fermions in transmission through a monolayer graphene barrier. Compared to the smallness of the lateral shifts in total reflection, the lateral shifts can be enhanced by the transmission resonances when the incidence angle is less than the critical angle for total reflection. It is also found that the lateral shifts, as the function of the barrier’s width and incidence angle, can be negative and positive in the cases of Klein tunneling and classical motion.4. Discuss the electronic transports in the asymmetric graphene superlattice consisted of a periodic potential structure and wide potential barrier, which are separated by an internal potential well. The results show that under a certain condition a novel transmission peak occurs in the original gap region at non-zero incident angles, and reveal that such asymmetric graphene superlattice containing a potential well can be equivalent to a double-barrier structure and two-coupled superlattices. Moreover, it has also shown that the controllable magnitude and width of the quantum well have a great effect on the electronic transmission and conductivity.更多还原