A. Gibaud

Influence of functional organic groups on the structure of CTAB templated organosilica thin films

Highly ordered mesoporous organosilica thin films containing functional organic terminal groups covalently bonded to the silica matrix were synthesized by co-condensation of tetraethylorthosilicate (TEOS) and organotriethoxysilane RSi(OEt)3 n (R = Cl(CH2)3, CN(CH2)3) in the presence of cetyltrimethylammonium bromide (CTAB) as structure directing agent under acidic conditions. The influence of the nature and concentration of these organic groups on the structure of the thin films is evidenced by Grazing Incidence Small Angle Scattering (GISAXS) and X-ray reflectivity. We show that the introduction of chloropropyl groups strongly affects the structure of these films while cyanopropyl groups weakly perturb it. In the case of the chloropropyl groups, the presence of trans and gauche conformers in the films is clearly evidenced by using micro-Raman spectrometry. Their effects on the phase behaviour versus the concentration are discussed.

Cheap and robust ultraflat gold surfaces suitable for high-resolution surface modification.

A simple procedure to elaborate robust ultraflat gold surface without clean room facilities is presented. Self-assembled 3-mercaptopropytriethoxysilane (MPTMS) on silicon was used as a buffer layer on which gold was sputtered using a common sputter-coating apparatus. The optimization of the sample position into the chamber of the sputtering machine yielded the formation of a thin (approximately 8 nm) gold layer. The characterization of the resulting gold surface (i.e., AFM, X-ray reflectivity, and diffraction) has demonstrated its high smoothness (<0.7 nm) over a large scale with a preferred (111) orientation. The robustness of the substrate toward organic solvents and thermal treatment was also tested. The ability of these surfaces to be used as substrates for high-resolution surface modification was confirmed by functionalizing the gold surface using the dip pen nanolithography process.

Neutron and X-ray reflectivity analysis of ceramic-metal materials

Neutron and X-ray reflectivity measurements of a thin film of cermet (ceramic-metal) made by co-sputtering Pt and Al2O3 on the surface of a flat piece of float glass are presented. From the analysis of the specular and off-specular measurements, the morphology of the Pt clusters which are embedded in the Al2O3 matrix is determined by adjusting a model to the observed data. It is found that the structure of such films presents a certain degree of order in the direction normal to the surface of the films but no correlation (or with a very short correlation length not measurable by this technique) in the plane of the film.

TIME-RESOLVED IN SITU GISAXS EXPERIMENT OF EVAPORATION-INDUCED SELF-ASSEMBLY OF CTAB TEMPLATED SILICA THIN FILMS UNDER CONTROLLED HUMIDITY

The influence of controlled humidity on the phase transformation of CTAB templated silica thin films is studied by time-resolved in situ GISAXS measurements. It is shown that during a short period of time the silica matrix is flexible enough to follow the morphologic changes of the cylindrical micelles into spherical ones. During this time water can be uptaken and outtaken from the film. The evolution of the lattice parameters upon cycling dry and humid air is presented and discussed.

Analysis of X-ray reflectivity curves of non-Gaussian surfaces

Surfaces of symmetric diblock copolymers thin films exhibiting non-Gaussian distribution of height are studied by X-ray reflectivity and atomic force microscopy (AFM). When deposited on a silicon substrate, the surface is essentially flat and its roughness may be described by a Gaussian distribution of height. Upon annealing, films operate a two-dimensional phase transformation and form islands at the free surface having height and size that evolve as a function of annealing time. The height probability function cannot be represented by a Gaussian distribution anymore, and the question that arises is how to take into account the morphology of such surfaces in the reflectivity calculations. In a first approach, we show that the height distribution function derived from AFM measurements is directly transferable to analyze X-ray reflectivity curves according to a formalism that we present. In a second part, we determine the height distribution function from a fit to the observed reflectivity.