Application Example

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IntroductionTransmitted electrons scattered in different angles represent different types of information that arises within a thin foil in scanning transmission electron microscopy.The Bright Field (BF) signal typically represents Bragg-diffrac-tion orientation contrast and absorption contrast on thin foils.The Dark Field (DF) contains partly orientation contrast and material contrast on light elements.The High Angle Dark Field (HADF) contains maximum in-formation about material contrast and minimum Bragg-dif-fraction contrast. The scattering angles depend on the sample material, the foil thickness and the energy of the beam.

Retractable STEM DetectorThe new linear retractable STEM detector design is optimized for maximum manipulation capabilities with the sample, in-cluding a change of working distance or eucentric tilt above the detector.

Variable Angular DistributionDuring the change of the working distance the angular dis-tribution of electrons detected by detector segments is also changed. Therefore, the sample can be easily navigated to a maximum contrast condition, by using the working distance, see Fig. 2.

Color STEMThe three channels (BF, DF, HADF) can be acquired simul-taneously with the possibility of live color coding with no information loss.

Performing scanning transmission electron microscopy (STEM) in a scanning electron microscope (SEM) is a popular

technique for laboratories without transmission electron microscopy (TEM) capabilities. The new option for TESCAN

STEM detector extends the imaging capabilities by simultaneous acquisition of multiple signals from transmitted

and diffracted electrons including bright field, dark field and high angle dark field. The STEM analysis can be further

supplemented with transmission EDX or EBSD microanalysis for receiving higher resolution, utilizing the available

analytical techniques of the SEM.

High resolution analysis ofthin foils using the STEM Detector with HADF

c Fig. 1: Schematic drawing of the new STEM detector with HADF.

φ represents the scattering angle.

c Fig. 2: Distribution of accepted scattering angles by detector

segments, varying with the working distance on a non-immersion

microscope.

TESCAN ORSAY HOLDING, a.s.Libušina tř. 21, 623 00 Brno - Kohoutovice / Czech Republic

(phone) +420 530 353 411 / (email) sales@tescan.cz / marketing@tescan.cz www.tescan.com

Application Example High resolution analysis of thin foils using the STEM Detector with HADF

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c Fig. 3: Bright field image with diffraction contrast on dislocations

in ferritic steel (MIRA FEG-SEM).

c Fig. 5: ColorSTEM image on a FIB- prepared lamella of the

corrosion growing through Cr plating on a steel sample. Image

using mixing the three STEM signals as color channels: Red=BF,

Green=DF, Blue=HADF

c Fig. 6: STEM + EDX analysis of the corrosion sample shown in Fig. 5. c Fig. 7: Individual STEM signals from corrosion sample.

c Fig. 4: Dark field image of a rat intestine (MAIA FEG-SEM).

BF

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HADF

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