Topographic and Compositional Analysis in SEM with Backscattered Electron Imaging

In EBSD analysis, backscattered electrons vary in their intensity and direction depending on the topography and composition of the specimen. The contrast of the backscattered electron image is based on several factors such as the atomic number (Z) of the sample material, the acceleration voltage of the primary beam and the specimen angle (tilt) with relation to the primary beam.

The specimen angle is the main parameter for understanding topographic imaging. The Phenom’s backscattered detector of the Phenom SEM is mounted close to the sample, under the objective lens. The detector is split into four quadrants.

Topography Imaging

The two types of information contained in the backscattered electron image can be separated by electronically pairing the opposing quadrants. It is possible to obtain information on sample composition and topography. The two images are from the same material, showing the compositional mode as in Figure 1 and the topographical mode as in Figure 2.

Figure 1. BSE imaging in compositional mode

Figure 2. BSE imaging in topographical mode

Subtraction of the quadrants will offer topographic information, and operating the detector quadrants in pairs and then adding the signals will provide compositional information about the sample. Rotating the signal pairing enables the operator to effectively ‘shine the light’ on the sample from two different directions, over-under and left-right.

Figure 3 shows the principle of the compositional full mode, where all quadrants are active.

Figure 4 shows the topographical B mode principle, which indicates the over-under illumination capabilities.

The use of the over-under mode will show a strong shadow effect like the sun shining on an object as can be seen in the two corresponding images. Both images show the letter ‘S’ (Specimen - Spanish Euro coin) taken in compositional (full) mode as shown in Figure 5 and topographical B mode as shown in Figure 6. Switching between the two modes is done via the software.

Figure 3. Schematic representation of the Phenom detection system in compositional (full) mode

Figure 4. Schematic representation of the Phenom detection system in topographic mode

Figure 5. Image of the letter S (Euro coin) in compositional imaging mode

Figure 6. Image of the letter S (Euro coin) in topographical imaging mode

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The Phenom desktop SEM combines superb imaging power up to 100,000x and outstanding technical performance with better depth of focus and chemical contrast. It is the smart, affordable and market’s fastest solution that enables engineers, technicians, researchers and educational professionals to investigate micron and submicron structures.

With the Phenom proX we offer integrated, powerful EDS microanalysis to complete the optical performance of our SEM-range. Any Phenom system can be tailored to suit application and sample needs by choosing one of the many Pro Suite-based software solutions or specially designed hardware accessories.

Phenom-World helps you to stay competitive in a world where critical dimensions are continuously getting smaller. The Phenom desktop SEM offers direct access to the high-resolution and high-quality imaging necessary in a large variety of applications. It is an affordable solution that enables engineers, technicians, researchers and educational professionals to visualize micron and submicron structures.

This information has been sourced, reviewed and adapted from materials provided by Phenom-World BV.

For more information on this source, please visit Phenom-World BV.