Résumé
We present an investigation of large, isolated, graphene ribbons grown on the
C-face of on-axis semi-insulating 6H-SiC wafers. Using a graphite cap to cover
the SiC sample, we modify the desorption of the Si species during the Si
sublimation process. This results in a better control of the growth kinetics,
yielding very long (about 300 microns long, 5 microns wide), homogeneous
monolayer graphene ribbons. These ribbons fully occupy unusually large terraces
on the step bunched SiC surface, as shown by AFM, optical microscopy and SEM.
Raman spectrometry indicates that the thermal stress has been partially relaxed
by wrinkles formation, visible in AFM images. In addition, we show that despite
the low optical absorption of graphene, optical differential transmission can
be successfully used to prove the monolayer character of the ribbons.