BACK SCATTER ELECTRON (BSE) Rev. 0313

Transcription

1 Back-scatter Electron Secondary Electron BACK SCATTER ELECTRON (BSE) Rev. 0313

2 Contents BSE Introduction (3) Mounting the Detector (4) Load the Sample (5) Back-Scatter Settings (6-7) Optimize Image (8) Image Capture (9) Finishing (10)

3 Introduction The backscattered electron (BSE) detector is used to see z-contrast in materials. For best results the sample should be cut and polished smooth to eliminate any topographic contribution to the contrast. The detector is extremely fragile and must be mounted in the operating position by a staff person before you pump down the chamber. Please notify an NTUF engineer when you book the appointment and arrange to have the detector installed.

4 Mounting the Detector This procedure is to be done by NTUF staff only. BSE detector in parked position. When not in use the detector is kept in the parked position at the back of the chamber. A staff person will mount it beneath the probe lens for you. It is very delicate and must be handled correctly. When the detector is in position it reduces the clearance by 2mm, so great care must be taken when loading the sample and calibrating the stage height. BSE detector in operating position below the probe lens.

5 Load the sample Samples must be flat and mounted on a flat stub. It isn t possible to tilt or angle the sample for BSE imaging. Secure the stub with the stage mount screw and measure the clearance with the height adjustor. View of the mounted detector from below Stage switch should be in A position. Watch the clearance under the CCD as you close the chamber. The detector is extremely fragile and hangs 2mm below the probe lens. Do not let anything touch or brush against it.

6 Back-Scatter Settings Turn ON preamp offset. This will increase the brightness of your images. Set Beam Current 20kV, spot 5 recommended 7kV, spot 4 minimum It is more difficult to generate BSE signal so you need at least 7kV and spot 4. If the high tension you want is not available from the drop down menu, select HT presets and add it to the list.

7 Position the Sample When vacuum status is OK, open the column valve and calibrate the stage height according to standard protocol. Follow the Stage Calibration procedure in the SEM Training Manual to raise your sample to 5mm. Optimize the beam at 5mm with the SE (standard) detector. Chose a magnification that will allow you to see the microstructure. Switch to Back-scatter Detector When SE image looks good change to BSE. Chose Slow Scan 2 from Scan Tab. Push the F3 key to display the Videoscope or click the icon.

8 Optimize Image Videoscope Set Contrast to 100% and Brightness to 0%. 100% White 100% Black The dotted lines on the video scope represent the upper and lower limits of the ideal grey scale. Increase Brightness until screen is grey (~25%). Decrease Contrast to darken image (~95%). Fine tune brightness and contrast to stretch the videoscope trace from 100% white to 100 black.

9 Image Capture Preamp noise varies widely with scan parameters and filter presets. Try a standard F2 capture first (33.2 msec, 968 lines, Avg. 4 frames) If the image shows preamp noise and artifacts, the use the Integrate Filter: From the Filter menu pick Filter Presets. Chose Mode > Integrate Slow Scan Set Frames to 16, 32, or 64 Click OK To collect the image chose Filter > Integrate The screen will go dark and the image slowly appears as frames accumulate. The integration is complete when the snow flake turns yellow.

10 Finishing Transfer the frozen image to Scandium and return to live imaging by selecting SlowScan 2. When you are done imaging, call a staff person to park the BSE detector. Please reset the software to default conditions Detector Tab > SE Beam Tab > 5kV & Spot size 3 Videoscope OFF (F3) or pick the icon Reset any change to Scan or Filter Presets Export TIFF files to Coral Member drive (M:) Reset hardware to default conditions Close Column Valve Vent Chamber Preamp Offset to OFF Unload Sample Wait for Staff to park BSE detector Pump empty chamber Scandium TIFF export