Pure hydrogen low-temperature plasma exposure of HOPG and graphene: Graphane formation?
Single- and multilayer graphene and highly ordered pyrolytic graphite (HOPG) were exposed to a pure hydrogen low-temperature plasma (LTP). Characterizations include various experimental techniques such as photoelectron spectroscopy, Raman spectroscopy and scanning probe microscopy. Our photoemission measurement shows that hydrogen LTP exposed HOPG has a diamond-like valence-band structure, which suggests double-sided hydrogenation. With the scanning tunneling microscopy technique, various atomic-scale charge-density patterns were observed, which may be associated with different C-H conformers. Hydrogen-LTP-exposed graphene on SiO(2) has a Raman spectrum in which the D peak to G peak ratio is over 4, associated with hydrogenation on both sides. A very low defect density was observed in the scanning probe microscopy measurements, which enables a reverse transformation to graphene. Hydrogen-LTP-exposed HOPG possesses a high thermal stability, and therefore, this transformation requires annealing at over 1000 °C.
Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056, Basel, Switzerland.
Baran
B
Eren
Dorothée
D
Hug
Laurent
L
Marot
Rémy
R
Pawlak
Marcin
M
Kisiel
Roland
R
Steiner
Dominik M
DM
Zumbühl
Ernst
E
Meyer
HOPG; graphane; hydrogenation; plasma