Synthesis of 3C-SiC nanocrystals at the SiO2/Si interface by CO2 thermal treatment.

We report 3C-SiC nano-crystals synthesis by thermal annealing of SiO2/Si wafers in CO2 gas. The nano-crystals have been characterized using scanning electron microscopy and atomic force microscopy. These results are correlated with selective area electron diffraction paterns, and transmission electron microscopy observations that evidence the formation of cubic SiC nano-crystals epitaxied on Si. In our experimental conditions, the crystals size is in the range 10-60 nm, increasing with the treatment time, as the crystals density. Using isotopic labelled SiO2 associated with Nuclear Reaction Analysis (NRA) and Nuclear Narrow Resonance Profiling (NRP), oxygen exchanges between CO2 and SiO2 could be evidenced.

Superconducting transition at 38 K in insulating-overdoped La2CuO4-La1.64Sr0.36CuO4 superlattices: evidence for interface electronic redistribution from resonant soft X-ray scattering.

We use resonant soft x-ray scattering (RSXS) to quantify the hole distribution in a superlattice of insulating La2CuO4 (LCO) and overdoped La2-xSrxCuO4 (LSCO). Despite its nonsuperconducting constituents, this structure is superconducting with T_{c}=38 K. We found that the conducting holes redistribute electronically from LSCO to the LCO layers. The LCO layers were found to be optimally doped, suggesting they are the main drivers of superconductivity. Our results demonstrate the utility of RSXS for separating electronic from structural effects at oxide interfaces.