Reactions of homonuclear diatomic ions with metal surfaces. II. Nitridation of Al, Cu, Mo, and Ni by N+2 beams in the low kinetic energy-near threshold region
Nitridation of Al, Cu, Mo, and Ni to produce very thin nitride surface films is induced by 0–50 eV mass selected N+2 beams. The efficiency of nitridation, monitored by the KL2L2 nitrogen Auger electron signal, exhibits a large kinetic energy Ek dependence below ∼30 eV. The threshold impact energy fo...
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Veröffentlicht in: | The Journal of chemical physics 1982-06, Vol.76 (12), p.6417-6424 |
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Hauptverfasser: | , , , , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Nitridation of Al, Cu, Mo, and Ni to produce very thin nitride surface films is induced by 0–50 eV mass selected N+2 beams. The efficiency of nitridation, monitored by the KL2L2 nitrogen Auger electron signal, exhibits a large kinetic energy Ek dependence below ∼30 eV. The threshold impact energy for nitridation varies for the different metals; it is nominally zero for Al and Ni, ∼4 eV for Mo, probably ≳0 for Cu, and does not occur at any energy below 200 eV for Ag. That the metal electronic structure is a critical parameter is evidenced by the facts that different ion doses are required to produce similar nitride signal levels on various metals and that plots of nitride intensity versus Ek exhibit structure or at least different shapes in the low Ek region. A simple quantum mechanical model [J. Chem. Phys. 76, 6408 (1982)] is used to simulate the nitridation reaction by delineation into four elementary steps: (1) neutralization of incoming N+2, (2) decomposition of N2 into 2N, (3) de-excitation and thermalization of N, and (4) chemical reaction proper. Least-squares fitting of the theoretically predicted dissociation efficiency versus Ek to experimental data provides estimates of the fraction of N+2 neutralizations occuring by resonance or Auger neutralization processes. |
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ISSN: | 0021-9606 1089-7690 |
DOI: | 10.1063/1.442998 |