覆氧或氧离子轰击下固体表面二次正离子发射的研究

Secondary Positive Ion Emission from Solid Surface under Flood Oxygen or Oxygen Primary Ion Bombardment

通过对离子轰击下固体表面电离过程重新考虑认为，在固体表面覆氧或氧离子轰击下除表面原子的直接电离外，激发态双原子间电子交换和断键亦起重要作用。在此基础上修正了局部热力学平衡模型，得到了一个包含各类离子内配分函数、电离能、金属－氧原子键断键能以及表面金属原子与氧原子结合份数等参数决定的新电离几率分析表达式。应用该分析表达式解释了金属表面覆氧、氧离子轰击金属、化合物半导体表面二次离子发射中氧增强效应、充氧量对二次离子发射的影响及其基体效应等实验现象。并由此得到了元素相对灵敏度因子的分析表达式，对化合物半导体及一些陶瓷材料表面二次离子质谱分析中元素灵敏度因子随元素电离能变化曲线给予了相应的物理解释。

Electron exchange between two atoms in excited states and bond cleavage under bond oxygen or oxygen primary with argon ion bombardment are also important surface ionization processes other than the direct ionization of atoms in the surface layers.As a result of the revision of the local thermodynamic equilibrium model,a new analytical expression of the ionization probability, including the partition function of the particles,ionization potentiol,metal-oxygen bond cleavage energy,the fraction of metal atom to combined oxygen, etc.,has been presented in this paper.This theoretical model on secondary positive ion emission is helpful for the explanation of experimental phenomena,such as enhanced secondary positive ion yields with flood oxygen,escondary positive ion yield dependence on the flood oxygen pressure, and matrix effects in secondary ion massspectrometry (SIMS).From this model,an expression of the relative sensitivity factor(RSF)of SIMS has been derived. The relationship between RSF of semiconductors and ceramic surface and ionization energy of elements can be interpreted in the light of this model.