Optimised EBSD Analysis with the SUPRA® FE-SEM - Carl Zeiss

Optimised EBSD Analysis with the SUPRA ® FE-SEMWhite Paper

White PaperOptimised EBSD Analysis with the SUPRA ® FE-SEMAuthor:Carl Zeiss MicroscopyDate: March 2005IntroductionElectron Backscattered Diffraction (EBSD), also known asEBSP, BKD or OIM, is a SEM technique applicable tocrystalline materials. It provides absolute crystal orientationinformation down to the nano scale level when a dedicatedField Emission SEM is used. EBSD allows identification ofphases and discrimination between phases in materials. TheEBSD patterns are produced when an electron beam strikesa specimen surface. The electron scattering in the materialcauses electrons to travel in all directions. Electrons thatsatisfy the Bragg condition, i.e. n=2d sin, for a crystalplane are channelled and show the Kikuchi bands, see fig.1.EBSD patterns were first observed by Kikuchi in a TEM. Forthe EBSD detection in a SEM a fluorescent phosphor screenin front of a highly sensitive CCD camera is used. The EBSDdetector system is mounted on one of the side ports ofthe specimen chamber and should bring the fluorescentscreen close to the specimen. For clear EBSD patterns thespecimen surface has to be distortion free. This can only beachieved with proper specimen preparation techniques likeelectro-polishing or using a focussed ion beam system likethe CrossBeam ® .Instrumentation requirementsIn order to enable EBSD in a FE-SEM, the EBSD detector hasto be mounted on the side port of the specimen chamber.The specimen has to be tilted to 70 degrees to project thepattern on the EBSD detector. Forward scattered BSE detectorsare mounted on the EBSD detector to enable phase andZ-contrast imaging of the specimen surface. In order tocombine chemical and phase identification an EDS detectorneeds to be installed facing towards the specimen at exactlythe same coincidence point as the EBSD detector.Figure 1Example of EBSD pattern.2

White PaperThe ZEISS SUPRA ® 55 and 55VP FE-SEMs both have integrateddesign features for superior EBSD analysis:■ GEMINI ® FE-SEM column supplies a highly stable electronbeam for fully automated analysis of large areas■ High Current, Depth of Field module with the virtualFE source moved to infinity (fig. 2) supplies a highlyparallel beam with a high current density enabling improvedlateral resolution (sub 10nm), high angular resolution(0.25º) and fast detection times (100 points/sec).■ Precise scan control and calculated compensation for tiltcorrection combined with dynamic focus gives distortionfree imaging, see fig.3■ Chamber geometry supplies an excellent platform forcoplanar EBSD and EDS analysis at 8.5mm WD andspecimen tilt of 70º, see fig. 4■ Eucentric specimen stage provides accurate tilt to 70ºand stability for large area automated phase detection■ Variable pressure capabilities to analyse non conductingspecimens like ceramics and semiconductors (for theSUPRA ® 55VP only)■ No magnetic field outside the GEMINI ® end lens eliminatesdistortions when analysing magnetic or para-magneticspecimensFigure 2GEMINI ®High Current modewith virtual parallel beam:optimised EBSD.Applications(courtesy of HKL Technology)EBSD analysis is an extremely useful technique for crystalorientation, phase identification (combined with EDS analysis),phase verification (like in duplex steels), texture measurement,boundary characterisation and deformation measurements.The following application examples have been provided byHTL Technology A/S, Hobro, Denmark.The instrumentation used for the EBSD analysis was theHKL Nordlys II EDSD Detector, Channel 5 software and theZEISS SUPRA ® 55VP FE-SEM.Figure 3Undistorted geometry at 700° tilt. Tilt correction on, dynamic focus not used!3

White PaperFigure 4Optimised EBSD geometry:EBSD and EDS detectorsclose to the specimen at70 degrees tilt.ChamberSE detectorVPSE detectorRoentec SDD EDS detectorGEMINI ® end lensHKL TechnologyNordlys II EBSDdetectorForescatter BSE detectorsSpecimen at 70 degrees tiltFigure 5Example of EBSDImaging of AngariaDelphinus shell whichhas an unstable CaCO 3(aragonite) structureunder the electronbeam. EBSD patternwhere taken with aspeed of 100 patterns/sec to minimise beamdamage.5a: Fore-scatter image.5b: EBSD Band Contrast.5c: Inverse pole figurecolouring (IPF).5d: Legende for IPF(right). Arogonitecrystal structure(above).adbc4

White PaperFigure 6Example of EBSD onduplex stainless steel.6a: Fore-scatter image.6b: EBSD Map.6c: Phase map: ferritegreen/austenite blue;6d: Recrystalised blue,deformed red.adbcFigure 7SUPRA ® 55VP FE-SEMwith the HKL TechnologyNordlys EBSD detector.5

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