Advanced materials nanocharacterization

This special issue of Nanoscale Research Letters contains scientific contributions presented at the Symposium D "Multidimensional Electrical and Chemical Characterization at the Nanometer-scale of Organic and Inorganic Semiconductors" of the E-MRS Fall Meeting 2010, which was held in Warsaw, Poland from 13th to 17th September, 2010

Multiscale investigation of graphene layers on 6H-SiC(000-1)

In this article, a multiscale investigation of few graphene layers grown on 6H-SiC(000-1) under ultrahigh vacuum (UHV) conditions is presented. At 100-μm scale, the authors show that the UHV growth yields few layer graphene (FLG) with an average thickness given by Auger spectroscopy between 1 and 2 graphene planes. At the same scale, electron diffraction reveals a significant rotational disorder between the first graphene layer and the SiC surface, although well-defined preferred orientations exist. This is confirmed at the nanometer scale by scanning tunneling microscopy (STM). Finally, STM (at the nm scale) and Raman spectroscopy (at the μm scale) show that the FLG stacking is turbostratic, and that the domain size of the crystallites ranges from 10 to 100 nm. The most striking result is that the FLGs experience a strong compressive stress that is seldom observed for graphene grown on the C face of SiC substrates

Multidimensional characterization, Landau levels and Density of States in epitaxial graphene grown on SiC substrates

Using high-temperature annealing conditions with a graphite cap covering the C-face of, both, on axis and 8° off-axis 4H-SiC samples, large and homogeneous single epitaxial graphene layers have been grown. Raman spectroscopy shows evidence of the almost free-standing character of these monolayer graphene sheets, which was confirmed by magneto-transport measurements. On the best samples, we find a moderate p-type doping, a high-carrier mobility and resolve the half-integer quantum Hall effect typical of high-quality graphene samples. A rough estimation of the density of states is given from temperature measurements

Micro-Raman and micro-transmission imaging of epitaxial graphene grown on the Si and C faces of 6H-SiC

Micro-Raman and micro-transmission imaging experiments have been done on epitaxial graphene grown on the C- and Si-faces of on-axis 6H-SiC substrates. On the C-face it is shown that the SiC sublimation process results in the growth of long and isolated graphene ribbons (up to 600 μm) that are strain-relaxed and lightly p-type doped. In this case, combining the results of micro-Raman spectroscopy with micro-transmission measurements, we were able to ascertain that uniform monolayer ribbons were grown and found also Bernal stacked and misoriented bilayer ribbons. On the Si-face, the situation is completely different. A full graphene coverage of the SiC surface is achieved but anisotropic growth still occurs, because of the step-bunched SiC surface reconstruction. While in the middle of reconstructed terraces thin graphene stacks (up to 5 layers) are grown, thicker graphene stripes appear at step edges. In both the cases, the strong interaction between the graphene layers and the underlying SiC substrate induces a high compressive thermal strain and n-type doping

Elaboration et caractérisation de composants type MOSFET en 4H-SiC orienté (11-20)

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Croissance en solution et caractérisation de monocristaux de carbure de silicium cubique

Ces travaux portent sur la croissance de mono cristaux massifs de 3C-SiC sur des germes hexagonaux de SiC. Cette étude a permis la mise au point d'un procédé de croissance en solution à basse température sans creuset utilisant une zone fondue de solvant (silicium). L'analyse des vitesses de croissance mesurées a permis de montrer que le transport de soluté à travers la zone de solvant jusqu'à l'interface de croissance est assuré par un régime convectif. L'épaisseur des couches réalisées est limitée par la formation des inclusions de silicium. Celles-ci sont la conséquence de l'apparition, sous l'effet du transport convectif, d'une surfusion constitutionnelle du liquide qui est Il à l'origine de la déstabilisation morphologique du front de croissance. Des caractérisations optiques et structurales ont permis l'étude de l'évolution de la qualité des couches obtenues en fonction des paramètres expérimentaux optimisés.This work deals with the bulk growth of 3C-SiC single crystals using hexagonal SiC substrates. We developed a crucible free solution growth process using a silicon solvent zone and low temperature. The analysis of the growth rate vs growth temperature and thickness of the molten Si zone showed that the transport of the solute through the solvent zone to the growth interface is ensured by a simple convection model. The thickness of the grown layer is limited by the incorporation of solvent particles. This incorporation of silicon is the result of two phenomena: parasitic nucleation ahead of the growth interface and/or morphological instability of the growth front itself. Both occur as a result of the development of constitutional super-cooling in the liquid phase. The effect of the growth parameters on the quality of the grown crystals was studied using several optical and structural characterizations.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Sensors based on interfaces

International audienc

Spectroscopie des fautes d'empilement dans 4H-SiC

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF