C₆₀⁺ Secondary Ion Microscopy Using a Delay Line Detector

Abstract

Buckminsterfullerene (C(60)) as a primary ion for secondary ion mass spectrometry (SIMS) has shown many benefits over classical SIMS sources in the analysis of large organic molecules including many of biological significance. One constraint has been the limited focusing capabilities of the C(60)(+) beam. Although this could be circumvented by using beam size limiting apertures at the cost of beam current, high-resolution imaging using conventional time-of-flight (TOF) instruments has been challenging and time-consuming. We present a method in which we combine the use of an unfocused C(60)(+) beam with an ion optical microscope. A delay line detector is used to obtain fully resolved hyperspectral data sets that contain both the full mass spectral and the localization information. The obtained image resolving power is 4 microm at a pixel size of 250 nm. Microscope mode C(60)(+) imaging was shown to resolve micrometer-scale features in a combined polymer-tissue sample. Our new approach demonstrates high-quality SIMS imaging using the full C(60)(+) beam current. This results in equal or better resolving power at reduced acquisition speed.

Mass Spectrometric Imaging for Biomedical Tissue Analysis

“…The development of softer primary ion beams such as C 60 + , SF 5 + , Bi 3 + , Au n + , Cs n + 23,24 extend the applicability of SIMS for larger M w species. These polyatomic primary beams are able to desorb secondary ions from the sample surface without extensive fragmentation.…”

Microscope mode secondary ion mass spectrometry imaging with a Timepix detector

“…These detectors provide both time and space information for all ions simultaneously. 24,25 However, they lack sufficient multi-hit capability and the image reconstruction is time-consuming. The latter makes the instrument tuning and optimization difficult because of a lack of direct image feedback.…”

Fast, high resolution mass spectrometry imaging using a medipix pixelated detector

“…The spatial resolving power [2,12], i.e., the sharpness sample feature edges, is typically calculated instead of the resolution in terms of pixel size (55 ϫ 55 m) and ion optical magnification (approximately a factor of 85 in SIMS and a factor of 42 in LDI) resulting in one pixel probing 650 ϫ 650 nm (SIMS) and 1.31 ϫ 1.31 m (LDI) on the sample surface, respectively. The spatial resolving power has been previously defined as the distance between 80% and 20% intensity of a feature within the image [2,12].…”

“…The spatial resolving power has been previously defined as the distance between 80% and 20% intensity of a feature within the image [2,12]. Testing our images against this criterion of resolving power is realized by making a line scan through the image intensity (Figure 4a and b).…”

“…Recently, an MCP stack combined with a delay-linedetector has been implemented in combination with a C 60 ϩ secondary ion mass spectrometry (SIMS) primary ion beam on an ion microscope for high spatial resolution MSI [11,12]. The spatial resolving power measured with this setup was 4 m. However, substantial signal processing is required to convert the timing signal for every hit on the delay-lines into position information.…”