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Negative cluster emission in sputtering of Si1−x Ge x alloys: A full spectrum approach

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Bibliographic Details
Title:	Negative cluster emission in sputtering of Si1−x Ge x alloys: A full spectrum approach
Authors:	Perego, M. hvwdp@yahoo.it, Ferrari, S.¹, Fanciulli, M.¹
Source:	Surface Science. Dec2005, Vol. 599 Issue 1-3, p141-149. 9p.
Subjects:	Germanium, Alloys, Metallic composites, Silicon
Abstract:	Abstract: The emission of negative cluster ions in sputtering of silicon, germanium and silicon–germanium alloys was investigated by time of flight secondary ion mass spectrometry using Cs+ ions at 1keV for sputtering and Ga+ ions at 25keV for analysis. Various homonuclear and heteronuclear (; Si n Ge−) anionic cluster species were studied and their abundance distributions as a function of cluster size n were determined in steady state conditions. Surprisingly with n >2 are less sensitive to Ge concentration than Si−. This implies that the variation of the secondary ion signals as a function of Ge concentration cannot be explained in terms of simple statistical considerations. Also clusters show a peculiar behavior. Very strong matrix effects were observed for Ge− with decreasing intensity at high germanium concentrations. An opposite behavior is followed by the other clusters whose intensities are proportional to the Ge content. Moreover at high germanium concentrations, the and anions exhibit signals higher than Ge−. Finally, we observed that the fractions of silicon and germanium atoms in the ionized fraction of the sputtered flux are equivalent to their elemental fractions in the alloy. This behavior suggests the possibility to establish a protocol for the quantification of germanium concentration that can be applied to any Si1−x Ge x alloy avoiding matrix effects. [Copyright &y& Elsevier]
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Database:	Engineering Source

Description
Abstract:	Abstract: The emission of negative cluster ions in sputtering of silicon, germanium and silicon–germanium alloys was investigated by time of flight secondary ion mass spectrometry using Cs+ ions at 1keV for sputtering and Ga+ ions at 25keV for analysis. Various homonuclear and heteronuclear (; Si n Ge−) anionic cluster species were studied and their abundance distributions as a function of cluster size n were determined in steady state conditions. Surprisingly with n >2 are less sensitive to Ge concentration than Si−. This implies that the variation of the secondary ion signals as a function of Ge concentration cannot be explained in terms of simple statistical considerations. Also clusters show a peculiar behavior. Very strong matrix effects were observed for Ge− with decreasing intensity at high germanium concentrations. An opposite behavior is followed by the other clusters whose intensities are proportional to the Ge content. Moreover at high germanium concentrations, the and anions exhibit signals higher than Ge−. Finally, we observed that the fractions of silicon and germanium atoms in the ionized fraction of the sputtered flux are equivalent to their elemental fractions in the alloy. This behavior suggests the possibility to establish a protocol for the quantification of germanium concentration that can be applied to any Si1−x Ge x alloy avoiding matrix effects. [Copyright &y& Elsevier]
ISSN:	00396028
DOI:	10.1016/j.susc.2005.10.002