Interaction of surface acoustic waves with epitaxial graphene

表面声波与外延石墨烯的相互作用

• 批准号: 242778186
• 负责人: Dr. Alberto Hernández-Mínguez
• 金额: --
• 依托单位: Paul-Drude-Institut für Festkörperelektronik (PDI)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/242778186?language=en
• 关键词: Interaction; surface; acoustic; waves; epitaxial

This project investigates the interaction of surface acoustic waves (SAWs) with epitaxial graphene (EG) layers on SiC. SAWs produce tunable strain and piezoelectric fields, which modulate the graphene band structure and interact strongly with carriers. The moving character of these fields is particularly interesting for capturing carriers and transporting them at a well-defined velocity. We will explore these features for the controlled transport of carriers and spins in graphene layers. This, in turn, requires a better knowledge of the momentum transfer process from SAWs to carriers in graphene, as well as the effect of the SAW-induced strain and piezoelectric fields into the electronic bandstructure and spin-splitting.The epitaxial graphene layers for the acoustic modulation experiments will be produced by the surface graphitization method. The investigations will be carried out on monolayer as well as multilayer graphene grown on the Si- and C- face of SiC, respectively. In all cases, the processing of the samples for the application of SAWs and measurement of electroacoustic currents will be done directly on the EG/SiC structure.The investigation of the interaction between SAW piezoelectric fields and carriers in graphene will be focused in the achievement of the non-linear regime, where a strong piezoelectric field induces a high modulation of the graphene charge density. In order to achieve this non-linear transport regime, intensity enhancement of the SAW piezoelectric field travelling along the EG/SiC structure will be explored, as well as the reduction of the average carrier density in graphene by displacement of the Fermi level towards the Dirac point. Under these conditions, the carriers will be strongly confined at the minimum of the piezoelectric energy, where they will move with the well defined SAW velocity.Graphene is also a promising candidate for spin information transport. Use of ferromagnetic source and drain contacts will allow spin injection and extraction into the graphene channel for its acoustic transport. Long spin relaxation times are expected in multilayer EG due to its low substrate-induced scattering and low spin-orbit coupling. This, together with the fast, well defined SAW velocity in SiC, should allow acoustic spin transport along distances of hundreds of micrometers.In addition to the piezoelectric field, the strain field propagating with the SAW is also a candidate for carrier control in graphene. Strain induced transport is expected to be especially important in multilayers, where the piezoelectric field of SAWs is strongly screened beyond the first layer. Finally, short-period strain waves are expected to modulate the graphene band structure along SAW propagation direction when the SAW wavelength is of the same order of magnitude as the carrier mean free path in graphene.

本计画研究表面声波与SiC上磊晶石墨烯层的互动。SAW产生可调应变和压电场，其调制石墨烯能带结构并与载流子强烈相互作用。这些领域的移动字符是特别有趣的捕获载体和运输他们在一个明确的速度。我们将探索这些功能的控制运输的载流子和自旋在石墨烯层。这反过来又需要更好地了解从SAW到石墨烯中载流子的动量转移过程，以及SAW引起的应变和压电场对电子能带结构和自旋分裂的影响。研究将分别在SiC的Si面和C面上生长单层和多层石墨烯。在所有情况下，SAW应用和电声电流测量的样品的处理将直接在EG/SiC结构上进行。SAW压电场和石墨烯中的载流子之间的相互作用的研究将集中在非线性区域的实现上，其中强压电场引起石墨烯电荷密度的高调制。为了实现这种非线性传输机制，将探索沿着EG/SiC结构行进的SAW压电场的强度增强，以及通过费米能级向狄拉克点的位移来降低石墨烯中的平均载流子密度。在这些条件下，载流子将被强烈地限制在压电能量的最小值处，在那里它们将以明确定义的SAW速度运动。石墨烯也是一种有希望的自旋信息传输候选材料。铁磁源极和漏极接触的使用将允许自旋注入和提取到石墨烯沟道中以用于其声学传输。由于多层EG的低衬底诱导散射和低自旋轨道耦合，预计其自旋弛豫时间较长。这与SiC中快速、良好定义的SAW速度一起，应该允许沿着数百微米的距离沿着进行声自旋输运。除了压电场之外，与SAW一起传播的应变场也是石墨烯中载流子控制的候选者。应变诱导的运输预计将是特别重要的多层膜，其中的SAW的压电场被强烈屏蔽超出第一层。最后，当SAW波长与石墨烯中的载流子平均自由程具有相同的数量级时，预期短周期应变波沿着SAW传播方向调制石墨烯带结构。