Gold-On-Carbon SEM Resolution test specimen on a pin stub 12.mm dia, 3.2x8mm pin. It has a particle size range from approximately 5 - 150nm. This calibration specimen provides a means of testing scanning electron microscopes.
Resolution test specimen with a particle size range from approximately 5 - 150nm.
This calibration specimen provides a means of testing scanning electron microscopes. The various sizes of the gaps between gold crystals grown on a graphite substrate allow tests for the resolution attainable under real operating
conditions: concomitantly, the samples can be used to assess the quality of grey-level reproduction at high resolution. Ideally, high resolution scanning microscopes should give good results in the gap test combined with good grey level reproduction. Medium-quality instruments may achieve a chosen gap resolution, but the grey-level production may be quite poor,
for example, only 4 or 5 grey levels may appear. Grey levels arise in the secondary electron mode due to differential signal collection and this originates from geometric irregularities on the test specimen. Hence, the angular crystal faces in the larger gold crystals in this specimen can be used
for the grey level assessment.
As an aid in use, there is an outline image of a square mesh on the surface of the specimen: this is useful for preliminary focusing at magnifications below x150. In addition, if the user wishes to preserve the specimen then tests can be done on known areas leaving other areas unirradiated. For a demanding assessment of the imaging qualities of the microscope, the microscopist may wish to view the very fine array of particles present in the boundary region between evaporated gold in the grid squares and uncoated graphite in the grid bars. When assessing the secondary electron image quality, the sample is best viewed using a specimen tilt of 30 degrees to the secondary electron collector. The degree of stage tilt used in back-scattered electron testing will depend on the position of the detector.
It is better not to view the sample in any mode with a tilt greater than 35 degrees since the height of the larger crystals may be such that the small crystals become shielded from view. If gap measurements are to be made it should be remembered that the magnification is not constant
throughout the image when the sample is tilted.
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