Atomic penetration into substrates

Of major interest for such processes as oxidation and compound formation are results that show several stages of atomic penetration into the substrate lattice. At metal surfaces, this appears to occur mostly with small atoms oxygen, nitrogen, carbon, as well as hydrogen. In some instances, as the coverage is increased, first an overlayer is formed (e.g. O on Ni(100)). Usually, the adatom occupies high-coordination sites such as hollow sites. On less close-packed surfaces, this site puts the adatom nearly coplanar with the surface metal atoms... 

Incorporation of Metal In certain cases, metal atoms, after their discharge, can penetrate into the substrate metal, forming alloys or intermetallic compounds in the surface layer and down to a certain depth. This effect has been known for a long time in the discharge of metals at liquid mercury, where liquid or solid amalgams are formed. In 1968 B. Kabanov showed that an analogous effect is present in metal ion discharge at many solid metals. 

Two specific illustrative cases of the extreme limits of behavior are given by Al deposition on CH3 and -COOCH3 terminated hexadecanethiolate/Au SAMs [20, 21]. The -CH3 terminated SAM case shows a spectrum of deposition modes, including penetration to the Au-SAM interface and ambient surface overlayer formation. The penetration was explained in terms of Al atoms diffusing into dynamically formed temporal vacancies in the SAM (see Sect. 2) caused by fluctuations of Au thiolate moieties around their equilibrium positions on the Au substrate [11-13]. Once the Al atoms arrive at the substrate, energetically favorable insertion into S Au bonds can occur. This in turn can result in strongly decreased... 

Ultimately, resolution in a sputtering process is limited by ion penetration into the substrate and/or by the range over which momentum can be transferred effectively enough to remove atoms from the sample surface. The diameter from which atoms can be sputtered has been reported to be about 10 nm for incident ion energies up to 12 keV (62). This means that it should be possible to fabricate structures of about 10 nm which also happens to be the size of the smallest ion beam that can be produced with present ion sources. 

No obvious evidence concerning substrate entry to the diiron cluster have been revealed indicating that the entry channel may be opened due to the proteins spontaneous flexibility or may be created by binding MMOB or MMOR (Wallar and Lipscomb, 1996). Recent data on crystal structure of MMOH from M. capsulatus demonstrate the geometric variability of the enzyme active site (Whittington et al., 2001). It is shown, that ferrous atoms, adjacent a-helix, and the Asn214 group have a certain pliability, which enables small molecules to penetrate into the active site. 

Ordered Monolayers and the Reasons for Ordering Adsorbate-Induced Restructuring Atomic Adsorption and Penetration into Substrates Metals on Metals Epitaxial Growth Growth Modes at Metal Surfaces Molecular Adsorption... 

In the case of Cu deposition, the initial persistence of the PET pealcs is believed to be related to Cu penetration into the polymer. A confirmation of the Cu atom incorporation underneath the PET surface has been obtained by Ion Scattering measurements. For Al deposited on PET, the ISS spectra show a well-defined single scattering peak due to collisions with Al surface atoms, whereas in the case of Cu deposition, only a broad distribution with a high energy edge at Che Cu kinematic factor is observed. This indicates that essentially no Cu atoms are present in the uppermost monolayer since mainly inelastic and multiple collisions sequences are detected. Diffusion of Cu into the polymer bulk has also been mentioned in the literature for polyimide B substrates. 

The sputtered atoms have a lot of energy. The initial atoms striking the surface may penetrate several atomic layers into the substrate, which helps to ensure... 

Information derivable from these techniques is of vital importance in the understanding of the atomic, molecular, ionic, solid-state, and electronic processes that occur at the surface and within the bulk of materials. The dynamics of ion and neutral species, as they approach, penetrate, charge-exchange, diffuse, dissociate (molecules and molecular ions), and sputter some of the substrate atoms, molecules, ions, and clusters, provides a wealth of information. Some of this information cannot be obtained by any other means. Although SIMS is now moving out of adolescence into a stage of matnrity, there is stiU much to be learned about the mechanisms and applications of SIMS and SNMS. 

L < o < 35 L The O forms the second contracting (increase Q2 from 0 to 4 %) ionic bond with a Cu atom (labeled 2) in the substrate second layer, the sp orbitals of the start to hybridize. The penetrates into the bulk meanwhile, the angle Z102 expands from 94.0° to 98.0°. 

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