Academia.eduAcademia.edu

Figure from:Investigation of polymer thin films by use of Bi-cluster-ion-supported time of flight secondary ion mass spectrometry

See full PDFdownloadDownload figure
Figure 5

Figure 5

Related Figures (4)

Fig. 1 SIMS spectra of PVP (right) and PMMA (lefi) for Bi’ (upper row) and Bis’ (lower row) primary ions (g-SIMS-relevant secondary io! fragments are indicated by the colored regions)
Fig. 1 SIMS spectra of PVP (right) and PMMA (lefi) for Bi’ (upper row) and Bis’ (lower row) primary ions (g-SIMS-relevant secondary io! fragments are indicated by the colored regions)
Fig. 2 Yield enhancement as a function of the cluster size: Total ion yield of PVP and PMMA for Bi,,’, n=1~7 primary ions (a); molecular ion yield of certain specific secondary ions as a function of the cluster size against the total ion yield (b)
Fig. 2 Yield enhancement as a function of the cluster size: Total ion yield of PVP and PMMA for Bi,,’, n=1~7 primary ions (a); molecular ion yield of certain specific secondary ions as a function of the cluster size against the total ion yield (b)
Fig. 3 Molecular ion yield ratio of PVP and PMMA for the corresponding primary ions: Ypiz/pii (eft), Ypisir (middle), and Ypizpis (right) Considering the low cluster size ratio, it is conspicuous for PVP as well as PMMA that Yp;2/z; decreases for the low-molecular-mass fragments. This indicates that signals in that region were not amplified as strongly as molecular fragments with higher masses. In a qualitative manner, this can be recognized for both materials, whereas the drop-off is located at different masses. Secondary ions with a molecular mass lower than m/z=50 can be assigned to it we consider the fine structure OF the molecular 10n yield ratio, certain specific fragmentation cascade is obvious. These line patterns can be explained by the subsequent addition or subtraction of single hydrogen atoms to or from the parent molecular species. Consequent- ly, it depends on the parent molecule itself if it is located at higher or lower masses of the cascade. Nevertheless, it is remarkable that larger cluster ions spread the molecular ion yield ratio of these parent-daughter fragments apart. For certain fragmentation cascades, this can be interrelated by a greater gain for the signal enhancement of the parent ion than that of the corresponding daughter molecular species. In the case of the CgH;" fragment, which corresponds to the polymer side chain of PVP, it can be seen that for Yp;5/z; the molecular ion yield for the daughter ions, e.g., CgH,” or C.H7*, is about 15% to 30% lower than for the corresponding parent fragment. Further investigations and experiments with respect to these fragmentation cascades are needed to get a better knowledge about the detailed underlying processes.
Fig. 3 Molecular ion yield ratio of PVP and PMMA for the corresponding primary ions: Ypiz/pii (eft), Ypisir (middle), and Ypizpis (right) Considering the low cluster size ratio, it is conspicuous for PVP as well as PMMA that Yp;2/z; decreases for the low-molecular-mass fragments. This indicates that signals in that region were not amplified as strongly as molecular fragments with higher masses. In a qualitative manner, this can be recognized for both materials, whereas the drop-off is located at different masses. Secondary ions with a molecular mass lower than m/z=50 can be assigned to it we consider the fine structure OF the molecular 10n yield ratio, certain specific fragmentation cascade is obvious. These line patterns can be explained by the subsequent addition or subtraction of single hydrogen atoms to or from the parent molecular species. Consequent- ly, it depends on the parent molecule itself if it is located at higher or lower masses of the cascade. Nevertheless, it is remarkable that larger cluster ions spread the molecular ion yield ratio of these parent-daughter fragments apart. For certain fragmentation cascades, this can be interrelated by a greater gain for the signal enhancement of the parent ion than that of the corresponding daughter molecular species. In the case of the CgH;" fragment, which corresponds to the polymer side chain of PVP, it can be seen that for Yp;5/z; the molecular ion yield for the daughter ions, e.g., CgH,” or C.H7*, is about 15% to 30% lower than for the corresponding parent fragment. Further investigations and experiments with respect to these fragmentation cascades are needed to get a better knowledge about the detailed underlying processes.
Fig. 4 G-SIMS spectra of PVP (upper row) and PMMA (lower row) on the basis of Bis" and Bi,” static SIMS spectra: g-SIMS spectra of PV! and PMMA for g=2 (left side) and g=5 (right side) rovide the demanded data for the g-SIMS procedure. static SIMS measurements with different primary ion pecies like Cs’ and Mn’ or Cs’ and Ar’ are able to ensure n even greater temperature difference and are known from iterature in that context [17—19]. Our approach is slightly ifferent. Instead of the direct energy variation of the rimary ions or the measurement with different primary ion pecies, we use different cluster sizes of Bi, to obtain the ow and high surface plasma temperatures, which are equired by the g-SIMS theory. It was believed that cluster ons are not suitable for the g-SIMS procedure due to the lifferent sputter mechanism of single atomic and cluster ion ombardment. To our knowledge, there is only one eference available at the moment where this problem has een described in context with the g-SIMS procedure [19]. Jnfortunately, no experimental details about the investigat- d sample system, cluster sizes, and measurement setups vere mentioned in that reference [19]. One problem could e that the combination of the cluster ions for the low and igh fragmented mass spectra was not suitable. It turned out hat for a data reduction approach according to the g-SIMS rocedure a certain difference in the cluster size is needed. ‘urthermore, it emerged during our experiments that Bi;", he most common Bi, cluster ion, is not a very good hoice for the g-SIMS procedure. The fragmentation pattern nd signal enhancement of Bi;° are very special and differ rom the other cluster ions. In the case of Bi;", not only ertain specific fragments were enhanced significantly but Iso a lot of other secondary ions obtain a remarkable ncrease of their secondary ion intensities. Hence, it is mportant to choose the right combination of cluster ions
Fig. 4 G-SIMS spectra of PVP (upper row) and PMMA (lower row) on the basis of Bis" and Bi,” static SIMS spectra: g-SIMS spectra of PV! and PMMA for g=2 (left side) and g=5 (right side) rovide the demanded data for the g-SIMS procedure. static SIMS measurements with different primary ion pecies like Cs’ and Mn’ or Cs’ and Ar’ are able to ensure n even greater temperature difference and are known from iterature in that context [17—19]. Our approach is slightly ifferent. Instead of the direct energy variation of the rimary ions or the measurement with different primary ion pecies, we use different cluster sizes of Bi, to obtain the ow and high surface plasma temperatures, which are equired by the g-SIMS theory. It was believed that cluster ons are not suitable for the g-SIMS procedure due to the lifferent sputter mechanism of single atomic and cluster ion ombardment. To our knowledge, there is only one eference available at the moment where this problem has een described in context with the g-SIMS procedure [19]. Jnfortunately, no experimental details about the investigat- d sample system, cluster sizes, and measurement setups vere mentioned in that reference [19]. One problem could e that the combination of the cluster ions for the low and igh fragmented mass spectra was not suitable. It turned out hat for a data reduction approach according to the g-SIMS rocedure a certain difference in the cluster size is needed. ‘urthermore, it emerged during our experiments that Bi;", he most common Bi, cluster ion, is not a very good hoice for the g-SIMS procedure. The fragmentation pattern nd signal enhancement of Bi;° are very special and differ rom the other cluster ions. In the case of Bi;", not only ertain specific fragments were enhanced significantly but Iso a lot of other secondary ions obtain a remarkable ncrease of their secondary ion intensities. Hence, it is mportant to choose the right combination of cluster ions