Frédéric Dulot

Preferential carbon etching by hydrogen inside hexagonal voids of 6H-SiC(0001)

6H-SiC(0001) samples have been etched in a hot-wall chemical vapor deposition reactor at a hydrogen pressure of 13 mbar at 1800 ° C . The surface morphology and elemental composition have been studied by scanning electron microscopy and micro-Auger analysis. Stoichiometric etching of SiC with equal atomic concentrations of Si and C is found on the flat sections of the surface, but in hexagonal voids of the SiC samples, a selective removal of C, leading to a pure Si surface at the bottom of the voids, is observed. Fast gas diffusion is the main transport mechanism for etching of the flat surface, while Knudsen diffusion becomes important inside the voids. It is proposed that the lower diffusion constant of reaction products containing Si compared to those containing C, leads to a preferential removal of C and a Si enrichment inside the voids.

STM-TIP induced surface diffusion of copper on copper (100)

Abstract We report various STM observations which demonstrate that a drastic change of the morphology of a metallic surface can be induced by the tip, at room temperature, even using so-called “standard” tunnelling parameters of about 1 V and 0.5 nA. The results on a 0.75-ML deposit of copper on Cu(100) highlight a strong amplification of the surface diffusion at room temperature. The time scale at which this phenomenon takes place excludes the effect of basic thermal activation. More surprisingly, we show that tip scanning can induce nucleation and growth of monoatomic islands from a bare copper (100) surface.

Controlled tuning of periodic morphologies on vicinal Si(111) surfaces

Regular hole patterns have been produced on vicinal Si(111) surfaces by optical lithography. Under heat treatment in ultrahigh vacuum, morphological rearrangements of the patterned surfaces occur. In situ light diffraction experiments were carried out during heat treatment to monitor the formation of the desired morphologies by an observation of the diffraction pattern. The surface morphology was characterized by different microscopy techniques after the heat treatment. Structured surfaces with periodic two-dimensional step arrangements and one-dimensional structures of atomically flat terraces uniformly separated by straight steps were obtained. The periodic structures extend over several μm.