Dual beam depth profiling of organic materials: assessment of capabilities and limitations

Abstract

With the advent of large argon cluster beams, organic materials can be sputtered without the accumulation of radiation damage. The dual beam mode with a Bi cluster analysis beam is successfully applied to depth profiling and 3D analysis of organic materials providing both high-depth resolution and high-lateral resolution. For the analysis of very small sample volumes, it is desirable that a rather large fraction of the material is consumed by the analysis beam and contributes to the analytical signal. However, at higher analysis beam sputter rates, the radiation damage by the Bi clusters can become quite severe leading to a molecular ion signal decay with depth. In this paper, we investigate the conditions for the optimum use of the sample material in the dual beam mode using the Irganox delta layer structure introduced by NPL (National Physical Laboratory (UK)). A model that describes the dual beam mode and allows calculating the intact area fraction in the steady state is presented. Yield volumes and damage volumes are determined for Bi 3 + and Bi 5 ++ as well as the useful sample fraction that contributes to the molecular ion signal. We will compare the results to the depth profiling with C 60 and Ar clusters in a single DC beam mode.

3D ToF-SIMS Analysis of Peptide Incorporation into MALDI Matrix Crystals with Sub-micrometer Resolution

“…The use of an Ar gas cluster ion beam (GCIB) [28] provides a means for uniform sputtering of organic materials without causing extensive degradation of the underlying material [29]. Therefore, combining an Ar GCIB for sputtering with a Bi cluster ion beam for analysis (dual-beam ToF-SIMS) can potentially allow one to obtain high-resolution 3D images from organic materials.…”

Visualizing molecular distributions for biomaterials applications with mass spectrometry imaging: a review

“…This process can be repeated using sequential sputter/analysis cycles and enable 3D chemical reconstruction of heterogeneous materials. Crucially, the achievable depth resolution can be as low as several nanometres, 64,65 providing almost a monolayer by monolayer representation of the material. In the sections below, we highlight a diverse array of applications of SIMS-MSI in materials chemistry with specific emphasis on biomaterials and their interactions.…”

Determination of the sputtering yield of cholesterol using Arn+and C60+(+)cluster ions

“…Niehuis et al 8 measured the depth resolution for a range of sizes of Ar clusters for sputtering organic multilayers. 10 These experiments are most often performed in the dual beam mode, 11 which has now become a standard operation mode in the analysis of organic and biological samples using time of flight (ToF) SIMS. With these developments, the number of studies utilising high-resolution imaging and 3D analysis of tissues and cells is rapidly growing and sub-cellular 3D imaging is now possible, as demonstrated recently by Passarelli et al, 10 who imaged the disposition of the drug amiodarone within macrophage cells.…”

“…With these developments, the number of studies utilising highresolution imaging and 3D analysis of tissues and cells is rapidly growing and sub-cellular 3D imaging is now possible, as demonstrated recently by Passarelli et al, 10 who imaged the disposition of the drug amiodarone within macrophage cells. 10 These experiments are most often performed in the dual beam mode, 11 which has now become a standard operation mode in the analysis of organic and biological samples using time of flight (ToF) SIMS. It encompasses, typically, a high-performance pulsed Bi cluster liquid metal ion gun (LMIG) applied for the analysis of the surface in the centre of the crater sputtered by the Ar clusters.…”