AVS 46th International Symposium
    Applied Surface Science Division Monday Sessions
       Session AS1-MoA

Paper AS1-MoA6
Secondary Ion Emission from LB-Layers Under Molecular Primary Ion Bombardment

Monday, October 25, 1999, 3:40 pm, Room 610

Session: Molecular Mass Spectrometry including Interpretation
Presenter: D. Stapel, Universität Münster, Germany
Authors: D. Stapel, Universität Münster, Germany
M. Thiemann, Universität Münster, Germany
B. Hagenhoff, TASCON GmbH, Germany
A. Benninghoven, Universität Münster, Germany
Correspondent: Click to Email
Secondary ion yields Y(X@sub i@@super q@) increase considerably when changing from atomic to molecular primary ions, whereas the simultaneous increase in the corresponding damage cross section @sigma@(X@sub i@@super q@) is much smaller. This holds in particular for thick molecular samples like LB multilayers or polymers. For LB multilayers we found yield increases up to a factor of 1000, when changing from Ar@super +@ to SF@sub 5@@super +@ bombardment. This phenomenon is important for practical analytical applications of TOF-SIMS, because yields, damage cross sections, and the resulting ion formation efficiencies E=Y/@sigma@ determine the achievable sensitivity as well as the achievable lateral resolution. The secondary ion emission of well defined model LB systems were investigated for a more detailed understanding of the complex sputtering and ion formation processes especially under different molecular primary ion bombardment. We investigated three series of LB layers (n=1, 3, 5, 7 ; n : number of monolayers) under 1 - 10 keV O@super +@, Ne@super +@, Ar@super +@, Xe@super +@, O@sub 2@@super +@, CO@sub 2@@super +@, SF@sub 5@@super +@, C@sub 7@H@sub 7@@super +@, C@sub 10@H@sub 8@@super +@, C@sub 6@F@sub 6@@super +@ and C@sub 10@F@sub 8@@super +@ bombardment. Y(X@sub i@@super q@) as well as @sigma@(X@sub i@@super q@) were determined. Our experimental results demonstrate a more pronounced yield and efficiency enhancement for multilayers (n>1). The increase in Y, @sigma@ and E features a saturation behaviour for molecular primary ion species containing more than 6 atoms. We could not find an influence of the chemical composition of the primary ion (SF@sub 5@@super +@/C@sub 7@H@sub 7@@super +@ e.g.) on this enhancement under static SIMS conditions. We compared the secondary ion and secondary neutral emission depths under atomic and molecular primary ion bombardment, and determined the influence of primary ion energy on secondary ion emission.