High-Resolution Chemical Snapshot with QUANTAX FlatQUAD

Scanning Electron Microscopy (SEM) imaging utilizes secondary electron (SE) and backscattered electron (BSE) detectors to observe the sample surface properties. SE imaging provides fine details of surface topography, while BSE imaging offers relative atomic contrast of the material. Image acquisition (~1024x786 px OR 1920x1080 px) in both modes typically takes 30 to 120 seconds, producing grayscale images without providing detailed chemical composition information about the material.

The XFlash^® FlatQUAD EDS detector features a unique geometry, where four SDD segments are placed directly below the pole piece in close sample proximity (~2–3 mm) and with a very high take-off angle (up to 80°). This geomtery gives the XFlash® FlatQUAD an exceptionally large solid angle, up to 1.1 sr, and unmatched sensitivity among SEM EDS detectors on the market. The high sensitivity and ultra-fast data acquisition speed delivers and exceptionally high output count rates (max. 3,200,000 cps). This enables users to acquire a so called “chemical snapshot” or single-frame EDS map of the sample surface to obtain corresponding to high-resolution chemical maps.

In addition to the typical high-resolution grayscale SEM image, the QUANTAX FlatQUAD system, an XFlash^® FlatQUAD detector and ESPRIT software, acquires a full EDS map at high resolution in a few seconds. The high-quality EDS map has an embedded SEM image, elemental distribution data, a full EDS spectrum for each pixel in the map. The spectra can be extracted from selected regions of the map for localized quantification, or the entire map can be quantitatively analyzed. Position-tagged spectroscopy, or “hypermap” enables comprehensive chemical analysis which is not possible with conventional SEM imaging.

In this example, a chemical snapshot was acquired in just 36 seconds using 15 kV accelerating voltage and 3 nA probe current. The input count rate exceeded 3,100,000 cps, with a total of 28 million counts collected in a few seconds.

Due to the highly heterogeneous nature of the material, comprising both low- and high-density elements, BSE imaging could not resolve some chemical variations in the material. On the other hand, chemical snapshot, or single frame EDS map provided clear chemical differentiation even at high mapping speeds. It is also interesting to note that with a relatively large field of view of 800x600 µm, features as small as 700 – 1400 nm in width were chemically resolved within the map.