Kiyoshi Kiuchi1 and Tatsuo Kondo1
1Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki
Molybdenum has a high reactivity with oxygen and forms the volatile oxide species i.e. (MoO3)n even under lower oxidizing conditions. It is an important problem as a synergistic effect of the chemical sputtering and the sublimation reaction. The present paper characterizes the effect of the oxidation on the sputtering of unalloyed molybdenum bombarded with A+ primary ions. SIMS was used to study the sputtering behaviors for thermally grown molybdenum oxide films bombarded with 2 keV A+.
Mo and MoO2 showed the essential behavior assumed by the physical sputtering. However, MoO3 showed the apparently chemical sputtering with two types of the secondary ion yield which depend on the density of the primary ion and sputtering time. One corresponds to the secondary ion yield originated from the covering layer of [(MoO3)n]ad.. The other corresponds to the secondary ion yield from the MoO3 solid surface. The secondary ion yield from [(MoO3)n]ad. is approximately twenty times as large as that from the bulk of MoO3. These dependence on the secondary ion yield are controlled by the primary ion density and sputtering time as a function of the thermodynamical reaction rate of n MoO3(Solid)\rightleftharpoons[(MoO3)n]ad.\rightleftharpoons(MoO3)n(Gas).
secondary ion yield, molybdenum, oxide film, secondary ion mass spectrometry, fusion reactor, kellogg diagram sublimation, argon, chemical sputtering, thermodynamical reaction
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