Low-energy reactive ion scattering as a probe of surface femtochemical reaction: H+ and H− formation on ionic compound surfaces

Abstract

Low energy ion beams for surface modification and film deposition AIP Conf. Proc. 576, 911 (2001); 10.1063/1.1395451 Molecular dynamics simulations of low-energy (25-200 eV) argon ion interactions with silicon surfaces: Sputter yields and product formation pathways Capture and loss of valence electrons during low-energy ͑50-500 eV͒ proton scattering from some alkali-halide surfaces such as LiCl, NaCl, and KF have been investigated in comparison with those from the TiO 2 ͑110͒ and Cs-adsorbed Si͑100͒ surfaces. The primary H ϩ ion survives neutralization when scattered from the highly ionized target species existing on the surface. For H Ϫ ion formation, a close atomic encounter with individual target ions is found to be important; the H Ϫ ion is formed more efficiently on the cationic site than on the anionic site despite the fact that the valence electron is spacially localized on the latter. This is because the charge state of scattered hydrogen is determined during a transient chemisorption state and amphoteric hydrogen tends to be coordinated negatively ͑positively͒ on the cationic site ͑the anionic site͒. The final charge state of scattered hydrogen is fixed at a certain bond-breaking distance ͑ϳ5.0 a.u.͒ from the surface where the well-defined atomic orbital of hydrogen evolves. The competing nonlocal resonance tunneling is suppressed at the ionic-compound surfaces due to the existence of a large band gap, so that hydrogen is scattered without losing the memory of such a transient chemisorption state.

TiO(001) single-crystal film formation by the incorporation of oxygen from MgO into the deposited Ti film

“…The possibility of electron transition by the AU process is determined by the competition between the interaction time of the He* at the surface (Ϸ10 Ϫ12 s) and the lifetime of the holes in the band, ϭh/W, where W presents the bandwidth. 24 In this estimation of the lifetime of the holes (Ϸ10 Ϫ15 s), the AU process seems unlikely to occur. Very recently, it was indicated by Morgner 25 that the Madelung potential caused the lifetime of the holes at the outermost surface to be longer than that in the bulk in the case of LiF and NaCl.…”

Charge exchange between low energy alkali ions and cerium oxide surfaces

“…Neutralization in large-angle alkali ion scattering is sensitive to the inhomogeneous LEP associated with electropositive and electronegative adsorbates on metal surfaces [13,[18][19][20][21][22][23][24][25][26][27][28][29], and should therefore also be useful in probing an inhomogeneous metal oxide surface [30]. Previous experiments investigating charge exchange between low energy projectiles and metal oxide surfaces [16,17] were performed in a small scattering angle configuration (67°), which does not allow for separation of scattering from different sites.…”

Femtosecond Electron Dynamics on Solid Surfaces Probed by Ion Scattering and Stimulated Desorption of Secondary Ions

“…The experimental results and discussion are given in Sec. 3. The mechanism of neutralization of protons and negative ionization of hydrogen is dealt with in Subsec.…”