On December 24, 2015, the 23rd meeting of the All-Russian Workshop “Graphene: Molecule and 2D Crystal” will present the following reports: Graphene Interaction in 5 Upper Layers of Pyrolytic Graphite, Electron Population of π-Bands in Each Layer.
On December 24, 2015, the 23rd meeting of the All-Russian Workshop “Graphene: Molecule and 2D Crystal” will present the following reports:
Graphene Interaction in 5 Upper Layers of Pyrolytic Graphite, Electron Population of π-Bands in Each Layer.
Aleksey Petrovich Dementyev,
Senior Research Fellow National Research Center “Kurchatov Institute”
N(E) CKVV Auger spectra (V=σsσpπ) were used to measure the electron population of π-bands in five upper layers of a fresh graphite sample by cleaving it. Depth profiling of π-band states in each of the 1-5 graphene layers was performed by changing the electron collection angle in 15° - 90° range. Electron population in π-bands in each of the 1-5 layers was measured with respect to the electron concentration in the σp-band, it varied from ≈ 0 in the upper layer to its value in graphite in the 5th layer. Different populations of π-bands were established in each of the 1-5 graphene layers after purification. The observed changes in the π-band are believed to be reasoned by the following mechanism.
1. In bulk HOPG graphenes interact through the pz-electrons of neighboring layers. The interaction results in pz → π-band transitions with the generation of p1-nz/πn steady state in each graphene layer, where n is the part of pz-electrons transited to the π-band.
2. After HOPG cleavage, πn population in the 1-4 graphene layers changes due to inverse πn → p1-nz transitions with the generation of a new steady πni in each of the 5 top layers.
Large Graphene Single Crystals Synthesis
Konstantin Nikolaevich Yeltsov, Doctor of Physics and Mathematics
Head of Department of Atomic Technology and Measurement at General Physics Institute of the Russian Academy of Sciences
A growth feature of two-dimensional materials (layered van der Waals crystals (for example, a single atom layer of graphite - graphene) on a solid surface is that they do not require an epitaxial (strong) bond with a substrate. Usually, it is sufficient that the substrate is smooth, and the reaction kinetics, when there is a preferential growth of one two-dimensional nucleus, is a pacing factor.
The lecture will address:
Epitaxial growth on a metal catalyst. Systems with a strong graphene-metal substrate interaction (Ni, Ru, Rh, Co, Re);
Non-epitaxial growth on a metal catalyst. Systems with a weak graphene-metal substrate interaction (Cu, Ag, Au, Pt, Ir);
Non-epitaxial growth on a semiconductor surface (Ge).