Electronic dynamics in unoccupied states of graphene

在这个项目中，石墨烯纳米带和石墨烯片生长在Ni（111）上，插入Au，和SiC（0001）上的未占电子态的动力学将被研究。的寿命的测量进行作为一个功能的费米能级以上的K和M点附近的能量。由于在布里渊区的这些部分中的电子的高平行动量，从Ti：蓝宝石激光辐射的高谐波产生获得的超短XUV脉冲必须用于激发态的光发射。具有飞行时间选项的二维延迟线探测器使我们能够测量未占用频带中的动量弛豫。我们预计在布里渊区的K点和M点附近会有不同的行为。相对于可见光或UV泵浦脉冲的XUV探测脉冲的时间延迟使我们能够跟踪这些动态。掺杂石墨烯的效果，相对于费米能级移动未占用的带，也应该研究仅与石墨烯弱相互作用的衬底。优先计划内的各种合作伙伴通过提供用于纳米带、Gr/SiC样品的定义生长的化学品和对动态行为的理论见解来实现这些目标。

In this project the dynamics in unoccupied electronic states of graphene nanoribbons and graphene sheets grown on Ni(111), intercalated with Au, and on SiC(0001) will be investigated. Measurements of the lifetimes are performed as a function of energy above the Fermi level in the vicinity of the K and of the M points. Due to the high parallel momentum of the electrons in these parts of the Brillouin zone ultrashort XUV pulses obtained from high harmonic generation of Ti:sapphire laser radiation have to be employed for the photoemission out of the excited states. A two-dimensional delay-line detector with time-of-flight option enables us to measure also the momentum relaxation in the unoccupied bands. We expect a different behavior near the K and M points of the Brillouin zone. A temporal delay of the XUV probe pulses with respect to visible or UV pump pulses enables us to trace these dynamics. The effect of doping the graphene, which shifts the unoccupied bands with respect to the Fermi level, shall also be studied for substrates which only weakly interact with the graphene. Various co-operation partners within the Priority Program contribute to reach these goals by providing chemicals for the defined growth of nanoribbons, Gr/SiC samples and theoretical insight into the dynamic behavior.