High-resolution high-sensitivity elemental imaging by secondary ion mass spectrometry: from traditional 2D and 3D imaging to correlative microscopy

Abstract

Secondary ion mass spectrometry (SIMS) constitutes an extremely sensitive technique for imaging surfaces in 2D and 3D. Apart from its excellent sensitivity and high lateral resolution (50 nm on state-of-the-art SIMS instruments), advantages of SIMS include high dynamic range and the ability to differentiate between isotopes. This paper first reviews the underlying principles of SIMS as well as the performance and applications of 2D and 3D SIMS elemental imaging. The prospects for further improving the capabilities of SIMS imaging are discussed. The lateral resolution in SIMS imaging when using the microprobe mode is limited by (i) the ion probe size, which is dependent on the brightness of the primary ion source, the quality of the optics of the primary ion column and the electric fields in the near sample region used to extract secondary ions; (ii) the sensitivity of the analysis as a reasonable secondary ion signal, which must be detected from very tiny voxel sizes and thus from a very limited number of sputtered atoms; and (iii) the physical dimensions of the collision cascade determining the origin of the sputtered ions with respect to the impact site of the incident primary ion probe. One interesting prospect is the use of SIMS-based correlative microscopy. In this approach SIMS is combined with various high-resolution microscopy techniques, so that elemental/chemical information at the highest sensitivity can be obtained with SIMS, while excellent spatial resolution is provided by overlaying the SIMS images with high-resolution images obtained by these microscopy techniques. Examples of this approach are given by presenting in situ combinations of SIMS with transmission electron microscopy (TEM), helium ion microscopy (HIM) and scanning probe microscopy (SPM).

Improving the Molecular Ion Signal Intensity for In Situ Liquid SIMS Analysis

“…It can provide elemental, isotopic, and molecular information with high sensitivity (ppb to ppm level) and good spatial resolution (down to sub-nm in depth resolution and~50 nm in lateral resolution) [9,10]. However, as a high vacuum technique, it has been traditionally used to analyze solid samples.…”

Current status and future directions for in situ transmission electron microscopy

“…More experimental parameters have to be controlled and measured (multimodal/multiscale measurements) that could be in the form of a built-in Raman spectrometer, secondary ion mass spectroscopy (SIMS) or other types of (optical) spectroscopy. 19, 46 Opening up the polepiece gap will leave more room near the sample to include additional probes and detectors, e.g. tomography plus one or more of the following capabilities: (a) Environmental cell ( with windows); (b) Heating, cooling, (c) Nano-biasing, and (d) Cryo box for frozen samples.…”

Numerical investigation of depth profiling capabilities of helium and neon ions in ion microscopy

“…Of particular interest is the preferential sputtering and atomic mixing for the different irradiation conditions to determine the depth resolving power for experimental conditions on the helium ion microscope (HIM). As such it contributes to the development of SIMS on the helium ion microscope [23–25] in order to extend its application to organic samples. The interest of this work is not limited to polymer samples, as they are also used as model samples for biological applications.…”