Since 2004, graphene attracts intensive attention from scientists and engineers all over the world. During the last decades, the research relates to graphene and other 2 dimensional (2D) materials are rapidly increasing. Approximately, ten thousand journal papers have been published after the discovery of graphene in relative topics widely spread. On the other hand, the simple graphene properties research is nearly completed. Researchers turn their attention to other 2D materials or Van der Waals heterostructures. By increasing the liberty and knowledge of 2D materials, the Van der Waals heterostructures can start to build something on this 2D wander land. In this thesis the Van der Waals heterostructures is based on graphene and some other well known 2D materials such as hexagonal boron nitride (hBN) to study fundamental physics and possible applications in near future. In this thesis, three published papers which are related to Van der Waals heterostructures have been included. The electronic properties of encapsulated graphene on different 2D crystals have been investigated by the capacitance spectroscopy. Several 2D crystals have been tested as a substrate such as MoS2, WS2, mica, LiNbO3...etc. The quality of encapsulated device is correlates the interface self-cleaning. Follow with the fundamental physics study employed by a simple Van der Waals heterostructure. Graphene and hBN is lattice aligned within 2 degrees in difference and creates a new superlattice structure which just like moire pattern happens while two similar patterns overlapped. The basic electronic properties do not vary at near Dirac point. Away from the first generation Dirac point, the superlattice structure affects the band structure in higher carrier concentration. In this paper, aligned graphene-hBN capacitors have been demonstrated to discover more fine details of these many-body interactions in this superlattice structure. The final part is related to twist controlled graphene-graphene resonance tunneling transistors. A Van der Waals heterostructure is constructed by two aligned graphene stripes with a thin layer of hBN as a spacer. The electrons are tunneled from one stripe to another graphene stripe while a bias voltage applied. The resonance tunneling is occurred when two graphene flakes are aligned at certain bias voltage. In this paper, we contribute the resonance tunneling to momentum conservation of tunnelling electrons. Theory simulation is highly agreed with our experiment results.
|Date of Award||1 Aug 2015|
- The University of Manchester
|Supervisor||Andre Geim (Supervisor)|