Confining electrons in graphene on hexagonal boron nitride

该项目的主要目标是探索不同的设备方案，以提高石墨烯量子点的质量，远远超出当前的标准。加强对量子点器件性质的控制，甚至可能控制量子点器件的形状，将允许新的复杂实验来研究少载流子区域的激发态谱以及电荷和自旋弛豫时间。所有建议的实验都集中在增加器件的可调性以及减少无序势的影响上。更具体地说，我们正在计划两类实验，旨在直接提高当今最先进的石墨烯量子点设备的质量，或者解决与体积和边缘粗糙度无序的影响相关的未解决的问题。在第一种情况下，我们将把我们最终的点设计与在六方氮化硼(HBN)薄层之间嵌入石墨烯纳米结构的技术结合起来，并使用局部金属顶栅来增加系统的可调性。这种器件的概念将特别应用于新的脉冲门实验，以研究石墨烯量子点的驰豫时间，但它有望成为一种总体上提高石墨烯器件质量的全球策略。第二类计划实验旨在解决更根本的问题，即薄片边缘在hBN上的双层石墨烯设备中所起的作用。为了做到这一点，我们提出了一种新颖的“类科比诺”器件方案，其中薄片的边缘可以完全从电流路径中排除。通过这两类实验，我们期望对理解单层和双层石墨烯纳米结构和量子点器件的输运性质做出重大贡献。

The main goal of this project is to explore different devices schemes for improving the quality of graphene quantum dots well beyond current standards. An enhanced control over the properties, and possibly even over the shape, of quantum dot devices will allow new sophisticate experiments to investigate excited state spectra in the few-carrier regime as well as charge and spin-relaxation times. All the proposed experiments focus on gaining increased device tunability as well as on reducing the influence of disorder potential. More specifically, we are planning two class of experiments, aimed either at directly improving the quality of today most advanced graphene quantum dot devices, or at addressing unsolved issues related to the influence of bulk and edge-roughness disorder. In the first case, we will combine our ultimate dot design with techniques for embedding graphene nanostructures between hexagonal boron nitride (hBN) thin layers, and employ local metallic top-gates to increase the systems tunability. This device concept will be applied in particular for new pulse-gate experiments to investigate relaxation times in graphene quantum dots, but it is expected to be a global strategy to improve the quality of graphene devices in general. The second class of planed experiments aims instead at addressing the more fundamental question of the role of flake-edges in bilayer graphene devices on hBN. In order to do so, we propose a novel "Corbino-like" device scheme, where the edges of the flake can be fully excluded from the current path. With both class of experiments, we expect make a significant contribution to the understanding of the transport properties of single- and bi-layer graphene nanostructures and quantum dot devices.