Issue 17, 2015

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

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.

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

Supplementary files

Article information

Article type
Paper
Submitted
30 Apr 2015
Accepted
09 Jul 2015
First published
10 Jul 2015
This article is Open Access
Creative Commons BY license

Analyst, 2015,140, 6005-6014

Author version available

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

A. J. Taylor, D. J. Graham and D. G. Castner, Analyst, 2015, 140, 6005 DOI: 10.1039/C5AN00860C

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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