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Sublimation of silver atoms from a nanometer-sized silver particle, namely, the crystalline-to-gas transition, has been directly observed by high resolution electron microscopy. Remarkable sublimation of silver atoms took place at 950 K from an approximately 9-nm-sized crystalline silver particle on the graphite substrate. The sublimation continued until the whole silver particle disappeared. No melting of the particle occurred during this process. The height-to-width ratio of a nanometer-sized silver particle on graphite at 950 K was about 0.65, and the ratio did not change so much during the sublimation-induced shrinkage of the particle.

We investigate the interaction of a carbon nanotube with a graphite substrate, using an interlayer potential that explicitly treats the registry dependence of the interaction. The carbon-carbon bond lengths in nanotubes differ slightly from those in flat graphite, so that the naively commensurate angular orientations for the tube with respect to the substrate lattice are destroyed. The interaction of a one-dimensional tube with a two-dimensional substrate then leads to an unusual registry phenomenon not visible in standard layer-on-layer growth: the system develops favorable orientations which clearly are incommensurate.

We present a quantitative study of the diffusion of spherical antimony clusters deposited on graphite surfaces. The experimental structures obtained during deposition are compared to predictions of recent computer models, and very good agreement is found. From this comparison we can obtain the diffusion coefficient of large antimony clusters containing around 2300 atoms moving on a graphite substrate: we find ${D\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}D}_{0}\mathrm{exp}({\ensuremath{-}E}_{a}/{k}_{B}T)$ with ${D}_{0}\ensuremath{\approx}1.6\ifmmode\times\else\texttimes\fi{}{10}^{4}{\mathrm{cm}}^{2}/\mathrm{s}$ and ${E}_{a}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.7\ifmmode\pm\else\textpm\fi{}0.1\mathrm{eV}$. This large value of ${D}_{0}$ suggests that the diffusion cannot be explained by a simple atomic activated process, but may rather involve collective motions of the atoms of the cluster.

The heat capacity of the ordering transition of helium films is studied on a new graphite substrate whose microcrystalline allignment and lateral size are ten times that for Grafoil. Transition peaks are considerably sharper than those observed on Grafoil allowing determination of critical parameters ..cap alpha..approx. =0.36 and A/sup +//A/sup -/ approx. =0.65. The ..cap alpha.. is substantially larger than recent three-state Potts-model calculations in two dimensions (of which the ordering transition is the only example), raising the possibility that the ordered state belongs to a new universality class.

La quantite d'exces superficiel Γ de SF 6 sur du graphite (mesure par methode volumetrique) augmente rapidement, au voisinage du point critique