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Why is sample mounting so important ?

This page was created by Jonas Michael-Lindhard with minor edits by Rebecca Ettlinger, DTU Nanolab

Sample mounting is much more important than many SEM users seem to think. If you can get away in 10 seconds with fixing the sample to a sample holder so that it will not fall off during the SEM session, the sometimes precious time that you have on the SEM is better spent operating the instrument - right? Well, not quite. In case you are in doubt, this page will explain you why.

Consider the benefits of a correctly mounted sample:

Safety of the instrument: A poorly mounted sample may encourage users to put the stage in a position that, in order to be able to take an image, puts the instrument health at risk - this must always be avoided.
Accessibility: You can 'access' the sample in a way that enables you to take the images you need: If, for instance, short working distance is needed to ensure optimum conditions for the Inlens detector, the sample must be mounted in a way that makes it possible.
Problems with charging are minimized: In most cases where users complain that the sample seems to be drifting, the reason is bad grounding due to sloppy mounting. Note: You can check the grounding of the stage prior to pumping the chamber down: Use a metal object to touch both the top of the stage and a lower part of the stage and listen for a high-pitched touch alarm. If there is no alarm, contact staff.
Limit the waste of time: Finding the right feature on a sample is more tricky than one would think due to the limited field of view. Making sketches of feature positions on the sample or drawing on the sample itself is often a great help.
Limit cross contamination issues: Sticking your sample onto a carbon pad that is already sitting on a pin stub is a very fast way to get started - but not a clever one. Using old carbon pads has many disadvantages:

You don't know what kind of samples have already been mounted so once your sample has been contact with an old carbon pad, it should be regarded as contaminated with anything.
The electrical conductivity of the carbon pad degrades over time and you will have charging problems.
The stickiness degrades over time and the sample may slide off.

Optimize imaging conditions hence image quality.: Poorly mounted samples are much more likely to vibrate or charge. This translate into poor image quality.

Respect the guidelines on sample mounting in the manual and you will maximize the results of your efforts at the SEM.

For a visual recap, review the sample mounting videos that are part of the training for new SEM users - they are found in the DTU Learn SEM TPT course under Contents.