Symmetric and asymmetric collision effects on the formation of singly and doubly-charged ions in sputtering process

S. Mondal; H. Gnaser; P. Chakraborty

doi:10.1140/epjd/e2012-30107-4

EPJ

Symmetric and asymmetric collision effects on the formation of singly and doubly-charged ions in sputtering process

S. Mondal¹^,a, H. Gnaser² and P. Chakraborty¹^b

¹ Surface Physics DivisionSaha Institute of Nuclear Physics, 1/AF Bidhannagar, 700064 Kolkata, India
² Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany

Received: 13 February 2012
Received in final form: 29 March 2012
Published online: 26 July 2012

Abstract

Measurements of Si²⁺ and Si⁺ ions sputtered due to bombardment of 3–5 keV Ar⁺ ions on silicon substrate have been performed for understanding exact charge-state formation mechanisms. Examination on the penetration depth dependence of incident particle on secondary ion formation has been performed. A closure look at the energetics of the secondary ions from their kinetic energy distributions suggests that Si⁺ ions are predominantly formed in the upper surface layer and Si²⁺ ions are produced due to target-target symmetric collision-induced Si 2p shell vacancy creation following the Auger electron emission. Furthermore, the increase in the oxygen-induced impurity in the silicon substrate enables us to explore the gradual transition from the dominating symmetric to asymmetric collision channel for production of Si²⁺ ions.

Key words: Atomic and Molecular Collisions

Present address: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, 980-8577 Sendai, Japan.

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EPJ

Symmetric and asymmetric collision effects on the formation of singly and doubly-charged ions in sputtering process

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