We report the direct formation of H2 and O pair ions through single collisions of water ions with metal surfaces at hyperthermal energies. This unusual intramolecular reaction proceeds also for heavy and semi-heavy water, producing molecular D2 and HD ions. The selectivity of this water splitting channel is estimated at being between 9 and 13% versus complete dissociation. The collision kinematics support the hypothesis of a water molecule colliding with a single surface atom, thereby forming an excited precursor (Rydberg?) state, which dissociates subsequently to form the molecular hydrogen ion with high kinetic energy. Inelastic energy loss considerations yield an estimate for the energy of the excited precursor state of ∼7 eV and ∼11 eV at low and high incidence energies. These energies are close to the à state (1B1, 7.5 eV) and state (1A1, 9.7 eV) of excited water (Rydberg states).

Using ab initio plane wave pseudopotential calculations, we study the energetics and structure of adsorbed linear arrays of oxygen and aziridine on carbon nanotubes, graphitic ribbons, and graphene sheets. Chemisorption of arrays of O or NH causes splitting of the CC bond and local deformation of the graphitic structures. The (3,3) nanotube cross section assumes a teardrop-like shape, while graphene sheets warp into a new local geometry around the chemisorbed molecules. The interior of a (3,3) nanotube is less prone to oxidation than the exterior because of steric effects. A zigzag (6,0) nanotube is less reactive and thus chemically more stable than an armchair (3,3) nanotube. The results suggest a partial explanation for the experimentally observed selective etching of metallic carbon nanotubes.

We have fabricated high aspect ratio, hydrophilic nanoelectrodes from individual single-walled carbon nanotubes (SWNTs) mounted on conductive atomic force microscope (AFM) tips for use as electrochemical probes. Individual SWNTs with an average diameter of 5 nm and up to 1.5 μm in length were passivated with nanometer-thick SiO2 films, deposited conformally in an inductively coupled plasma reactor. The electrically insulating SiO2 films improved the nanotube rigidity and stabilized the nanotube−AFM tip contact to enable use in aqueous environments. The nanotube tip was successfully exposed by subjecting the probe to nanosecond electrical pulse etching but only after electron beam irradiation in a transmission electron microscope (TEM). Probe functionality was verified by electrodepositing gold nanoparticles from aqueous solution only at the exposed tip.

Relative ion yields of low energy (320 eV) Ne+ ions scattered off a number of elemental surfaces are compared. Ion survival probabilities are seen to change significantly from one element to another depending on the surface work function, suggesting that resonant charge exchange between the metal conduction band and Ne 3s atomic level may be just as important as Auger neutralization processes. The observed yield dependence on work function is qualitatively explained using a description of resonant neutralization (RN) based on the Anderson model of an atomic level near a surface. Auger processes are found to be important in determining the final charge state of outgoing ions, while quasi-resonant interactions between the core atomic levels are seen to be nonexistent.

Etching of a patterned semiconductor surface in a plasma depends strongly on the transport of ion and neutral species between the features. Factors altering ion scattering at the sidewalls of high aspect ratio features, such as ion temperature, mask erosion, and charging, influence significantly the final profile shape. Models to describe the inelastic and reactive scattering at various surfaces, coupled to ion trajectory calculations in the sheath and between features, are used to illustrate the contribution of these factors to microtrenching and sidewall bowing. A transition in the profile shape from exhibiting microtrenching to having a rounded bottom is predicted as a result of plasma-induced charging in very high aspect ratio insulating masks.

For over 90 years, nitroxyl (HNO) has been postulated to be an important reaction intermediate in the catalytic oxidation of ammonia to NO and its by-products (N2, N2O), but never proven to form or exist on catalytic surfaces. Here we show evidence from reactive ion beam experiments that HNO can form directly on the surface of polycrystalline Pt exposed to NH3via Eley–Rideal abstraction reactions of adsorbed NH by energetic O+ and O2+ projectiles. The dynamic formation of HNO in a single collision followed up by prompt rebound from the surface prevents subsequent reactive interactions with other surface adsorbates and enables its detection. In addition to HNO, NO and OH are also detected as direct products in what constitutes the concurrent abstraction of three surface adsorbates, namely NH, N, and H, by O+ projectiles with entirely predictable kinematics. While its relation to thermal catalysis may be tenuous, dynamic HNO formation could be important on grain surfaces of interstellar or cometary matter under astrophysical conditions.

We report the direct formation of H2 and O pair ions through single collisions of water ions with metal surfaces at hyperthermal energies. This unusual intramolecular reaction proceeds also for heavy and semi-heavy water, producing molecular D2 and HD ions. The selectivity of this water splitting channel is estimated at being between 9 and 13% versus complete dissociation. The collision kinematics support the hypothesis of a water molecule colliding with a single surface atom, thereby forming an excited precursor (Rydberg?) state, which dissociates subsequently to form the molecular hydrogen ion with high kinetic energy. Inelastic energy loss considerations yield an estimate for the energy of the excited precursor state of ∼7 eV and ∼11 eV at low and high incidence energies. These energies are close to the à state (1B1, 7.5 eV) and state (1A1, 9.7 eV) of excited water (Rydberg states).