We report here in situ measurements of the evolution of the Ag(110) surface during Si growth, using scanning tunneling microscopy and grazing incidence x-ray diffraction. We provide compelling evidence of an Ag(110) surface reconstruction associated with the release of Ag atoms induced by the growth of Si nanoribbons. Our results are in agreement with a missing row reconstruction of the Ag layer underneath the nanoribbons. This challenges the current understanding of the Si growth on nonreconstructed Ag(110), interpreted within the framework of silicene models.

Three-dimensionally (3D) nanoarchitectured palladium/nickel (Pd/Ni) catalysts, which were prepared by atomic layer deposition (ALD) on high-aspect-ratio nanoporous alumina templates are investigated with regard to the electrooxidation of formic acid in an acidic medium (0.5 M H₂SO₄). Both deposition processes, Ni and Pd, with various mass content ratios have been continuously monitored by using a quartz crystal microbalance. The morphology of the Pd/Ni systems has been studied by electron microscopy and shows a homogeneous deposition of granularly structured Pd onto the Ni substrate. X-ray diffraction analysis performed on Ni and NiO substrates revealed an amorphous structure, while the Pd coating crystallized into a fcc lattice with a preferential orientation along the [220]-direction. Surface chemistry analysis by X-ray photoelectron spectroscopy showed both metallic and oxide contributions for the Ni and Pd deposits. Cyclic voltammetry of the Pd/Ni nanocatalysts revealed that the electrooxidation of HCOOH proceeds through the direct dehydrogenation mechanism with the formation of active intermediates. High catalytic activities are measured for low masses of Pd coatings that were generated by a low number of ALD cycles, probably because of the cluster size effect, electronic interactions between Pd and Ni, or diffusion effects.

Atomic layer deposition (ALD) was used to synthesize highly-conformal titanium nitride thin films using both thermal activation at 250°C and plasma activation at 200°C. Tetrakisdimethylaminotitanium (TDMAT) and ammonia have been utilized as precursors. The evolutions of the thickness and the roughness of the films with the number of ALD cycles have been monitored by spectroscopic ellipsometry and atomic force microscopy, respectively. A slight difference has been observed between thermal and plasma-enhanced ALD TiN films. The chemical composition of the resulting layers for the two activation modes has been investigated by X-ray photoelectron spectroscopy. It indicates a partial oxidation of the film and it shows that the oxide content depends on the activation method and varies with the deposition temperature. The studies of both morphology and crystalline structure carried out by electron microscopy and X-ray diffraction have revealed homogeneous and polycrystalline films for the two activation processes. Electrical measurements have shown that the films grown by plasma-activation exhibit a higher conductivity. Finally, the TiN films were grown on high aspect ratio templates such as anodic aluminum oxide membranes. It demonstrates that highly-conformal TiN thin films can even be obtained by plasma-assisted process within such narrow three-dimensional nanostructures. That was unexpected.

We demonstrate the preparation of functional ‘extremely thin absorber’ solar cells consisting of massively parallel arrays of nanocylindrical, coaxial n-TiO₂/i-Sb₂S₃/p-CuSCN junctions. Anodic alumina is used as an inert template that provides ordered pores of 80 nm diameter and 1–50 μm length. Atomic layer deposition (ALD) then coats pores of up to 20 μm with thin layers of the electron conductor and the intrinsic light absorber. The crystallization of the initially amorphous Sb₂S₃ upon annealing is strongly promoted by an underlying crystalline TiO₂ layer. After the remaining pore volume is filled with the hole conductor by solution evaporation, the resulting coaxial p-i-n junctions display stable diode and photodiode electrical characteristics. A recombination timescale of 40 ms is extracted from impedance spectroscopy in open circuit conditions, whereas transient absorption spectroscopy indicates that holes are extracted from Sb₂S₃ with a lifetime of 1 ns.