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Ion Induced Surface Alterations Due to Electronic Charge Exchange and Chemical Reactions
Author(s) -
Rabalais J. Wayne
Publication year - 1982
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198200066
Subject(s) - chemistry , ion , atomic physics , auger , nitride , excited state , auger electron spectroscopy , vacancy defect , kinetic energy , electron , analytical chemistry (journal) , crystallography , physics , organic chemistry , layer (electronics) , quantum mechanics , chromatography , nuclear physics
A general discussion of the phenomena that can occur during ion—surface encounters is presented and specific examples of charge exchange processes on LiF surfaces and chemical reactions of N + 2 on metals are shown. During rare gas ion bombardment of LiF, ejection of F + ions and excited Li atoms and the energy distributions of secondary F + ions can be correlated with Auger primary ion—surface charge exchange transitions determined by the potential energy of the primary ion vacancy and electron promotions resulting from close atomic encounters. 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 KL 2 L 2 nitrogen Auger electron signal, exhibits a large kinetic energy E k dependence below ca. 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 E k exhibit structure or at least different shapes in the low E k region. A simple quantum mechanical model is used to simulate the nitridation reaction by delineation into four elementary steps: (1) neutralization of incoming N + 2 , (2) decomposition of N 2 into 2N, (3) deexcitation and thermalization of N, and (4) chemical reaction proper.