Graphene on metal surfaces and hexagonal boron nitride

Abstract

Abstract In this thesis, procedures for chemical vapor deposition growth of graphene on rhodium and on hexagonal-boron nitride were developed. The systems were further characterized by an- gular resolved photoemission spectroscopy and scanning tunneling microscopy. A single atomic layer of graphite, so called graphene has gathered a lot of attention nowadays. Due to its high carrier mobility it has great potential for future electronics. Another appli- cation for graphene is related to its chemical inertness. It can serve as template for single molecule deposition. With these applications in mind, it is necessary to find suitable production methods to fabri- cate high quality, large scale graphene. Among various fabrication methods, chemical vapor deposition has turned out to be a possible route to meet the demanded criteria of graphene fabrication. The growth and characterization of graphene on Rh(111) and hexagonal-boron nitride are the content of this thesis. Graphene grown by chemical vapor deposition of 3-pentanone on Rh(111) leads to a largescale, uniform growth of graphene. A unique corrugation of the graphene layer is observed, which contains three depressions and a hill site within the unit cell. These three pockets have a diameter of roughly 1 nm and have therefore high potential to act as adsorption sites for single molecules. In contrast to the strongly bonded graphene on Rh(111), graphene on h-BN shows weak inter- action with the substrate. Growing graphene on h-BN demands different process parameters, since the metal surface is passivated by the h-BN layer, i. e. it requires higher activation energy (temperature) and higher pressure. The bonding of graphene to the h-BN/Cu(111) is weak enough, that the graphene and the h-BN layer keep their intrinsic lattice constant during the formation which differs by 1.6%. This results in formation of a large moir´ pattern with a lattice constant of 15.4 nm. The mismatch is also represented in the electronic band structure,where two Brillouin zones of different diameter are found for the two layers. The corrugated h-BN nanomesh on Rh(111) as a substrate for graphene formation exhibits a unique behavior during the formation process. Other than in the case of h-BN/Cu(111), the h-BN layer here undergoes a change during the graphene formation process. An intercalation of carbon between the h-BN layer and Rh and a diffusion of carbon into the Rh bulk leads to a weakening of the bonding and the h-BN layer looses its corrugated nanomesh character. In a second CVD process, graphene can be grown on this flat h-BN substrate.