Sputter yields of insulators bombarded with hyperthermal multiply charged ions
Sputter yields of insulators bombarded with hyperthermal multiply charged ions
复制标题
用高温多电荷离子轰击绝缘体的溅射产额
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
H. Winter
中科院分区：
文献类型：
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作者：
P. Varga;T. Neidhart;M. Sporn;G. Libiseller;M. Schmid;F. Aumayr;H. Winter
测量了高温高电荷态Arq+离子(Q=1-9)轰击Au、Si、GaAs、SiO_2、MgO、LiF和NaC l的总溅射产额。只观察到碱卤化物(LiF、NaC l)和一定程度上的SiO_2电势溅射(溅射产额随初级离子荷态的增加而提高)。所有其他靶都表现出正常的碰撞诱导溅射。由此可见，溅射机理显然不能用库仑爆炸模型来解释，因为在库仑爆炸模型中，绝缘体如氧化镁以及半导体如硅和砷化镓也应表现出与溅射产额有关的电荷态。碱金属卤化物和SiO_2是以强电子声子耦合而闻名的材料，其中价带中的电子激发通过形成自陷激子(STE)和/或自陷空穴(STH)来局域。在高电荷态离子的轰击过程中，表面前面、表面和下面的中和过程导致了STE和/或STH的形成。因此，势能溅射可以解释为电子刺激脱附(ESD)中众所周知的缺陷介导的溅射过程，其中STH和/或STE衰变到不同的色心导致中和阴离子的脱附。同样产生的中性阳离子要么蒸发(就像碱性卤化物的情况一样)，要么必须通过撞击的射弹进行动量转移而被移除。因此，在能量很低的SiO_2的情况下，很可能只有氧被增强溅射，表面富硅，潜在的溅射效应随着离子剂量的增加而减小。
The total sputter yield for Au, Si, GaAs, SiO2, MgO, LiF and NaCl bombarded with hyperthermal highly charged Arq+ ions (q = 1-9) has been measured. Only for alkali halides (LiF, NaCl) and to some extent for SiO2 potential sputtering (enhancement of the sputter yield with increasing charge state of the primary ion) has been observed. All other targets showed normal collision induced sputtering. From that result it is obvious that the mechanisms for sputtering can not be explained by the Coulomb explosion model, because in this model insulators like MgO and semiconductors like Si and GaAs should also show charge state dependence of the sputtering yield. Alkali halides and SiO2 are materials which are known for strong electron phonon coupling where electronic excitations in the valence band are localized by formation of self trapped excitons (STE) and/or self trapped holes (STH). During bombardment with highly charged ions the neutralization process in front of, at and below the surface causes the formation of STE and/or STH. Therefore the potential sputtering can be explained as a defect mediated sputtering process which is well known in electron stimulated desorption (ESD) where the decay of STH and/or STE into different colour centers leads at the end to the desorption of neutralized anions. The also created neutral cations are either evaporated (as it is the case for the alkali halides) or have to be removed by momentum transfer by the impinging projectiles. Therefore it is very likely that in the case of SiO2 for very low impact energy mainly only oxygen is enhanced sputtered, the surface is enriched in Si and the potential sputtering effect decreases with increasing ion dose.