Reconstructing accurate ToF-SIMS depth profiles for organic materials with differential sputter rates

Citation

Taylor, A. J.; Graham, D. J.; & Castner, D. G. (2015). Reconstructing accurate ToF-SIMS depth profiles for organic materials with differential sputter rates. Analyst, 140(17), 6005-6014. PMCID: 4532557

Abstract

To properly process and reconstruct 3D ToF-SIMS data from systems such as multi-component polymers, drug delivery scaffolds, cells and tissues, it is important to understand the sputtering behavior of the sample. Modern cluster sources enable efficient and stable sputtering of many organics materials. However, not all materials sputter at the same rate and few studies have explored how different sputter rates may distort reconstructed depth profiles of multicomponent materials. In this study spun-cast bilayer polymer films of polystyrene and PMMA are used as model systems to optimize methods for the reconstruction of depth profiles in systems exhibiting different sputter rates between components. Transforming the bilayer depth profile from sputter time to depth using a single sputter rate fails to account for sputter rate variations during the profile. This leads to inaccurate apparent layer thicknesses and interfacial positions, as well as the appearance of continued sputtering into the substrate. Applying measured single component sputter rates to the bilayer films with a step change in sputter rate at the interfaces yields more accurate film thickness and interface positions. The transformation can be further improved by applying a linear sputter rate transition across the interface, thus modeling the sputter rate changes seen in polymer blends. This more closely reflects the expected sputtering behavior. This study highlights the need for both accurate evaluation of component sputter rates and the careful conversion of sputter time to depth, if accurate 3D reconstructions of complex multi-component organic and biological samples are to be achieved. The effects of errors in sputter rate determination are also explored.

Keyword(s)

Manufactured Materials
Microscopy, Atomic Force
Polymethyl Methacrylate/*chemistry
Polystyrenes/*chemistry
Silicon/chemistry
Surface Properties

Notes

Taylor, Adam J
Graham, Daniel J
Castner, David G
P41 EB002027/EB/NIBIB NIH HHS/
EB-002027/EB/NIBIB NIH HHS/
England
Analyst. 2015 Sep 7;140(17):6005-14. doi: 10.1039/c5an00860c.

Reference Type

Journal Article

Secondary Title

Analyst

Author(s)

Taylor, A. J.
Graham, D. J.
Castner, D. G.

Year Published

2015

Date Published

1757203200

Volume Number

140

Issue Number

17

Pages

6005-6014

ISSN/ISBN

1364-5528 (Electronic)
0003-2654 (Linking)

DOI

10.1039/c5an00860c

PMCID

4532557