Biomedical subjects

Y Garreau

Publications and source records attributed to Y Garreau.

9 recordsLinked to original sources

PubMed2004

Structure of ferromagnetic CrAs epilayers grown on GaAs(001).

Magnetic and structural properties of CrAs epilayers grown on GaAs(001) by molecular beam epitaxy have been studied. CrAs epilayers are orthorhombic for all thicknesses investigated but show a structural transition from a metastable phase for very thin films, to the usual bulk MnP-type orthorhombic phase at higher thicknesses. At intermediate thicknesses, there is a predominance of the new phase, although a contribution from the usual CrAs bulk phase remains clearly present. These results strongly suggest that the ferromagnetic signal measured at room temperature comes from the new metastable orthorhombic structure with an expanded b-axis induced by the substrate strain.

Journal Article↗

PubMed2003

"Magic" heteroepitaxial growth on vicinal surfaces.

The step period (Lambda) of vicinal surfaces can be used as a new parameter for the control of metallic heteroepitaxial growth. This is evidenced here in the case of Ag/Cu(211). The deposition of 1 monolayer (ML) exhibits a c(2 x 10) superstructure leading to the formation of [111] steps in the Ag adlayer in contrast with the original [100] steps for the Cu substrate. This wetting layer can be viewed as a (133) Ag plane and it will be the starting point for the epitaxial growth. The deposition of 4 ML shows that the thin Ag film results homogeneous and no twins or stacking faults are detected. Moreover, the film grows along the [133] axis which is the orientation that minimizes the misfit between Cu(211) and the Ag film. Thus, the use of a regular stepped substrate allows one to select the crystallographic orientation of the growth and seems to be a way to avoid the creation of stacking faults.

Journal Article↗

PubMed2002

Measuring surface stress discontinuities in self-organized systems with X rays.

We have performed a grazing incidence x-ray diffraction study of the self-organized N/Cu(001) system. Diffraction satellites associated with self-organization are particularly intense around Bragg conditions of the bulk crystal. Bulk elastic relaxations due to surface stress discontinuities at domain boundaries are responsible for this feature. A quantitative analysis shows that these relaxations, computed by molecular dynamics or continuum elasticity, explain very well the whole diffraction study. A difference in surface stress of 7 N m(-1) between uncovered and N-covered regions of the Cu surface is shown to be the driving force for self-organization.

Journal Article↗

PubMed2000

Interplay between atomic and mesoscopic order on gold vicinal surfaces

Self-organization on Au(1,1,1) vicinal surfaces provides a unique opportunity to study the interplay between atomic and mesoscopic order. First, experimental results demonstrate the different interactions between steps and surface reconstruction on Au(1,1,1) vicinal surfaces. Depending on the step atomic structure, lines of discommensurations are found to be either parallel or perpendicular to the step edges. This leads to a complete understanding of the mesoscopic self-organization on theses surfaces, which drastically depends on the step structure. This points out the crucial role played by the edge energy cost which can monitor the faceting periodicity in a wide range of values.

Journal Article↗

PubMed1996