N. R. Gall

Intercalation of nickel atoms under two-dimensional graphene film on (111)Ir

Abstract Intercalation of Ni atoms under a two-dimensional graphene film (2DGF) on (111)Ir was studied in ultra high vacuum using high resolution Auger spectroscopy. Ni atoms were shown to be intercalated effectively at 900 to 1500 K, and a polylayer nickel film was shown to grow under the 2DGF. A relationship between a proportion κ of Ni atoms intercalated under 2DGF and temperature was determined and it was shown that κ decreases from ∼30% at 900 K to ∼3% at 1500 K.

Influence of surface carbon on the formation of silicon-refractory metal interfaces

Abstract The influence of different chemical forms of carbon on the character of processes taking place at Si-metal interfaces was shown. Carbon in the form of a surface carbide of W (or Re and Mo) in contact with silicon is expelled from the surface to the bulk of the metal, to form a solid solution, causing cleaning of the interface. Carbon in the form of a monolayer graphite film (on Ir or Re) at T K is impermeable to the adsorption of silicon atoms, assuming the formation and maintenance of a sharp, non-reactive interface. The same form of carbon at T > 900 K , on the contrary, is completely permeable to silicon and does not influence silicide formation. Heating the silicon and rhenium interface which contains carbon dissolved in the metal bulk to T > 1200 K leads to its fast precipitation on the interface, in the form of a monolayer graphite film. The same amount of carbon, depending on the sample prehistory, can appear in different chemical forms and influence the interface processes in opposite ways.

Intercalation of two-dimensional graphite films on metals by atoms and molecules

An analysis is made of some general laws governing a new physical effect, i.e., the spontaneous penetration of particles (atoms, C60 molecules) adsorbed on a two-dimensional graphite film on a metal (Ir, Re, Pt, Mo,...) to beneath the graphite film (intercalation). It is shown that atoms having low ionization potentials (Cs, K, Na) intercalate a two-dimensional graphite film on iridium at T=300–400K with an efficiency χ≈0.5, accumulating beneath the film to a concentration of up to a monolayer. Atoms having high ionization potentials (Si, Pt, Ni, C, Mo, etc.) intercalate a two-dimensional graphite film on iridium at T≈1000K with an efficiency, χ≈1, forming beneath the film a thick intercalate layer which is strongly bonded chemically to the metal substrate but is probably weakly bonded to the graphite monolayer by van der Waals forces. The presence of a graphite “lid” impeding the escape of atoms from the intercalated state up to record high temperatures T∼2000K leads to superefficient diffusion (with an efficiency close to one) of various atoms (Cs, K) into the bulk of the substrate (Re, Ir).

Regularities of intercalation of two-dimensional graphite films on metals by atoms and C60 molecules

Abstract This article is a brief review devoted to the intercalation of two-dimensional graphite films (2DGFs) on metals. It is shown that two types of intercalation of atoms into 2DGF depending on the ionization potential of the intercalate can take place, and regularities of both are described. A new physical picture for the mechanism of the intercalation process is proposed and described in detail. A new unusual result, the possibility of intercalation of C 60 molecules into 2DGF, is reported. C 60 molecules are shown to stay without disintegration up to 1200 K in contact with the iridium surface.

Topographic study by scanning-tunneling microscopy of a two-dimensional graphite film on \((10\bar 10)\)

AbstractTwo-dimensional graphite films on

Interaction of C60 molecules with a (100) Mo surface

(10\bar 10)

Surface sulfide on (100) W : formation, stability, absolute concentration of sulfur

were produced in ultrahigh vacuum by adsorption of benzene vapor on the metal heated to T=1800 K. High-resolution Auger spectroscopy used for the film characterization showed the film indeed to have graphitic structure and monolayer thickness. The surface topography was studied in air by scanning-tunneling microscopy. The monolayer thickness was confirmed, and it was shown that a two-dimensional graphite film has a complex topography featuring numerous hillocks with linear dimensions of ∼3000 Å and height differences of ∼300 Å, while retaining graphitic structure on the atomic scale. The lack of planarity of such a film at room temperature is considered to be due to deformation occurring under cooling from the temperature of formation down to 300 K, which is caused by the difference in thermal expansion coefficients between the graphite sheet and rhenium.

Surface carbides in the sequence of phase equilibria in a binary (Tungsten-carbon) system

Abstract Auger-electron spectroscopy was used to study oxygen adsorption on C60 molecules film on (100)Mo. It appeares that one monolayer of C60 molecules does not completely protect metal substrate from oxidation, and one needs thin C60 film with thickness of 2-3 ML for complete reduction of oxygen penetration to the substrate from gas phase.