Résumé:

We have investigated graphene layers grown on 6H-SiC(000-1) under Ultra High Vacuum and under controlled atmosphere (600mb AR pressure, 2000°C). The UHV growth gives a thin system with an averaging thickness given by Auger spectroscopy between one and two graphene planes. The growth under AR pressure shows multilayer samples with an average thickness larger than 5 graphene planes. Already from the first layer, a significant rotational disorder is revealed by electron diffraction (LEED), although well defined preferred orientations exist. For the multilayer samples, STM studies show the presence of “ponds” (with lateral size <100 nm) separated by “ridges” of height 0.7 nm. Combined micro-differential transmission and micro-Raman spectroscopy confirm these results. The analysis of the so-called D, G and 2D bands give a good estimation of the thickness, the quality of the films and the stacking of the multilayer samples. Transport measurements have been performed using Van der Pauw design of 2.8 mm by 2.8 mm and hall bar structure of 1μm by 6μm. The mobility of the multilayer samples (around 0.8 m2V-1s-1) is larger than the one of the almost monolayer but seems to reveal a relative electronic coupling between the different graphene planes. At low temperature (4k), the low field magneto resistance is consistent with the weak localisation correction.