Regensburg 2002 – wissenschaftliches Programm
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O: Oberflächenphysik
O 4: Oberfl
ächenreaktionen (I)
O 4.3: Vortrag
Montag, 11. März 2002, 11:45–12:00, H43
Electronic excitation of metal surfaces exposed to a nitrogen radical beam — •Detlef Diesing1, Johannes Berndt2, and Jörg Winter2 — 1Heinrich-Heine-Universität Düsseldorf — 2Anwendungsorientierte Plasmaphysik, Ruhr-Universität Bochum
Metal surfaces exposed to a nitrogen radical beam may be excited by the recombination reaction N + N → N2 + Δ E . One open question still is, whether the excess energy Δ E is delivered either adiabatically to the phonons of the metal or non adiabatically to electron-hole pair excitations. During the oxidation reaction of low work function metals (for example magnesium) electronic excitations are well know and investigated [1]. On noble metal surfaces the electron emission can hardly be detected since the work function is high. A possible solution is the internal detection of electronic excitations by Schottky diodes[2]. In the present work tunnel diodes are used to detect the electronic excitation of 20 nm thick copper films in a nitrogen radical beam. The beam is produced by a surface wave sustained microwave discharge which may contain also higly vibrationally excited nitrogen molecules N2(ν >> 1). By a chopping unit in the radical beam we could detect chopped tunnel currents, which clearly correlate with the plasma parameters as microwave power and gas flow density. The transients of the chemically induced tunnel currents are discussed. [1] T.Greber, Surface Science Reports, 28 (1997) 1 [2] B. Gergen et al., Phys. Rev. Lett. 82 (1999) 446