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A possible solution to the problem of compositional change with ion‐bombarded oxides
Author(s) -
Bertóti Imre,
Kelly Roger,
Mohai Miklós,
Tóth András
Publication year - 1992
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.740190155
Subject(s) - x ray photoelectron spectroscopy , nitride , chemistry , ion , crystallography , analytical chemistry (journal) , nuclear magnetic resonance , physics , organic chemistry , layer (electronics) , chromatography
We have explored a new type of experiment in which the beam‐induced surface changes of MgO, SiO 2 , Al 2 O 3 , TiO 2 , V 2 O 5 and MgAl 2 O 4 are determined by XPS after ion bombardment at 2.5 keV with Ar + or N 2 + . The initial bombardment, typically with Ar + , led to a combined surface cleaning and loss of O. Although the relative extents of these were difficult to establish, the result was in every case to define the composition in an N‐free situation. After a subsequent bombardment with N 2 + the O content was distinctly lower than that after Ar + impact, with the extra O deficiency in each case made up almost exactly by the N addition. For example, Al 2 O 3 evolved from a nominal Al 2 O 2.74 to a nominal Al 2 O 2.20 N 0.48 . The chemical state of this N was predominantly nitride‐type, indicative of MN bonds (M, metal). The observed replacement of MO bonds with MN bonds is disfavoured by thermodynamics and this, combined with the already mentioned tendency for the extra O loss to be closely matched by the N addition, together constitute a strong indication that the disturbed lattice is to some extent relaxing randomly. Interestingly, however, the extent by which N replaces O increases as the energy change calculated for this replacement decreases . This confirms, in agreement with a large body of earlier work, that the changes in the oxides are to some extent also chemically guided. The similarity to ion beam mixing and to ion‐beam‐induced grain growth is worth noting, where again one finds a mixture of ballistic (i.e. random) and chemically guided behaviour.