Early stages of the HFCVD process on multi-vicinal silicon surfaces studied by electron microscopy probes (SEM, TEM)

In this paper, we show that silicon dimples are suitable samples to study diamond nucleation on a controlled distribution of defects by SEM FEG and HRTEM observations. Indeed, multi-vicinal surfaces generated by a UHV thermal treatment have been characterised by STM experiments. On these terraces, we observed a strong increase of the nucleation density higher than two orders of magnitude compared to pristine silicon samples. Moreover, a preferential location of diamond nuclei along the steps is reported. This result is explained by the large surface diffusion length of carbon species compared to the terrace's width. Indeed, during the early stages of growth, oriented silicon carbide nano-crystals are observed with the relationship SiC(220)//Si(220)

Trojan-like internalization of anatase titanium dioxide nanoparticles by human osteoblast cells

Dentistry and orthopedics are undergoing a revolution in order to provide more reliable, comfortable and long-lasting implants to patients. Titanium (Ti) and titanium alloys have been used in dental implants and total hip arthroplasty due to their excellent biocompatibility. However, Ti-based implants in human body suffer surface degradation (corrosion and wear) resulting in the release of metallic ions and solid wear debris (mainly titanium dioxide) leading to peri-implant inflammatory reactions. Unfortunately, our current understanding of the biological interactions with titanium dioxide nanoparticles is still very limited. Taking this into consideration, this study focuses on the internalization of titanium dioxide nanoparticles on primary bone cells, exploring the events occurring at the nano-bio interface. For the first time, we report the selective binding of calcium (Ca), phosphorous (P) and proteins from cell culture medium to anatase nanoparticles that are extremely important for nanoparticle internalization and bone cells survival. In the intricate biological environment, anatase nanoparticles form bio-complexes (mixture of proteins and ions) which act as a kind of ‘Trojan-horse’ internalization by cells. Furthermore, anatase nanoparticles-induced modifications on cell behavior (viability and internalization) could be understand in detail. The results presented in this report can inspire new strategies for the use of titanium dioxide nanoparticles in several regeneration therapies

Effect of annealing on properties of CuInS

Surface morphology, structural and optical properties of CuInS2 thin films grown by the single source thermal evaporation in vacuum have been studied. The films were annealed from 250 to 550 °C in argon atmosphere with low oxygen concentration (O2 < 2 ppm). CuInS2 films are characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and optical transmittance and reflectance spectra. The maximum grain size of the sample after annealing at 550 °C was over 150 nm. The electron dispersion spectroscopy and X-ray analysis concludes that the polycrystalline CuInS2 thin film after annealing above 200 °C were sulphur-poor. We obtain CuInS2 layers with high structural and optical quality at annealing temperature above 450 °C with formation of In2O3 as minority phase. The band gap energy of the CuInS2 films after annealing above 450 °C was about 1.50 eV which perfectly matches the solar spectrum for energy conversion

Characterisation of ordered mesoporous carbons and their MCM-48 silica templates obtained by the replication technique using different carbon infiltration processes

International audienc

Growth and optimization by post-annealing of chalcopyrite CuAlS

The chalcopyrite CuAlS2 compound was grown from stoichiometric melt by horizontal Bridgman method. The obtained ingots were crushed finely and annealed at different temperatures from 800 °C to 1100 °C under a gas mixture of 5% N2/H2 atmosphere. X-ray diffraction and Raman spectroscopy were used to investigate the layer microstructures, as well as their lattice vibration spectra. The layers were characterized by scanning electron microscopy (SEM) and the compositional analyses were done by energy dispersive X-ray microanalysis (EDX). Raman measurements of the as made powder indicated seven prominent peaks at 205, 250, 290, 340, 369, 418 and 457 cm−1 with large intensity at 457 cm−1. The peaks at 205, 250, 340 and 457 cm−1 were ascribed to B2 modes while the peaks 369 and 418 cm−1 were ascribed to E modes. The peak at 290 cm−1 may be assigned to the A1 mode. After annealing, the Raman features become better and phonon mode at 290 cm−1 looks more distinct. The stoichiometric CuAlS2 compound was obtained when the sample was annealed at 900 °C

Study of the structural evolutions of mesoporous MCM-48 silica infiltrated with carbon by different techniques

International audienc

Comparative structural analysis of mesoporous silica FDU-12 with 3D-TEM, XRD refinement and gas sorption porosimetry

Congrès du 05.08.2006 au 07.08.200

Characterisation of nano-structured titanium and aluminium nitride coatings by indentation, transmission electron microscopy and electron energy loss spectroscopy

International audienceTitanium and aluminium nitride Ti1 − xAlxN films deposited by radiofrequency magnetron reactive sputtering onto steel substrate are examined by transmission electron microscopy over all the range of composition (x = 0, 0.5, 0.68, 0.86, 1). The deposition parameters are optimised in order to grow nitride films with low stress over all the composition range. Transmission electron microscopy cross-section images of Vickers indentation prints performed on that set of coatings show the evolution of their damage behaviour as increasing x Al content. Cubic Ti-rich nitrides consist of small grains clustered in rather large columns sliding along each other during indentation. Hexagonal Al-rich films grow in thinner columns which can be bent under the Vickers tip. Indentation tests carried out on TiN and AlN films are simulated using finite element modelling. Particular aspects of shear stresses and displacements in the coating/substrate are investigated. The growth mode and the nanostructure of two typical films, TiN and Ti0.14Al0.86N, are studied in detail by combining transmission electron microscopy cross-sections and plan views. Electron energy loss spectrum taken across Ti0.14Al0.86N film suggests that a part of nitrogen atoms is in cubic-like local environment though the lattice symmetry of Al-rich coatings is hexagonal. The poorly crystallised domains containing Ti and N atoms in cubic-like environment are obviously located in grain boundaries and afford protection of the coating against cracking