Year: 2010
Type: article
Abstract: The influence of lithium (Li) exposures on monolayer graphene grown on the silicon-terminated SiC(0001) surface is investigated using low-energy electron microscopy, photoelectron spectroscopy, and micro-low-energy electron diffraction. After Li deposition, islands or Li droplets are observed on the surface, and are found to coalesce together with time. Formation of a dipole layer at the interface, interpreted to originate from Li-Si bonding, is observed directly after Li deposition, and manifested by a 2 eV shift of the $\text{C}\text{ }1s$ and $\text{Si}\text{ }2p$ bulk SiC peaks. This indicates that Li atoms penetrate through the graphene and carbon buffer layer directly after deposition at room temperature since three $\ensuremath{\pi}$ bands are then moreover observed at the K point, instead of the single $\ensuremath{\pi}$ band for monolayer graphene. The existence of three $\ensuremath{\pi}$ bands is interpreted as a mixture of bilayer and monolayer graphene plus a difference in doping levels due to an uneven distribution of Li atoms. Li gives rise to electron doping of the graphene and results in a lowering of the Dirac point. After annealing to a few hundred degrees Celsius, a more even Li distribution and intercalation is obtained since then two distinct $\ensuremath{\pi}$ bands appear at the K point.
Source: Physical Review B
Institutions: Linköping University, Lund University
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W1990268166