SPI Gold Foil Thin Film Apertures

Use these self-cleaning apertures for superior TEM performance

We hope you will consider becoming a regular customer for the world known SPI Supplies Gold Foil Thin Film Apertures. These apertures are made to a standard actually beyond what is normally required for the typical TEM installation, as they are used in increasing numbers in certain SEM and Critical Dimension measuring instruments that require absolutely no pin holes in the thin film surrounding the central hole.

Please note the following:

Unpacking

The apertures are placed in a case specially made to virtually eliminate any possibility for there to be damage during shipment. If, for some reason, after removing the aperture from this transport and storage box , it is necessary to replace the aperture in the box, then always place the visible gold part of the aperture facing the lower part of the case.

Never try to grip the aperture directly on the lower part of the box (e.g. the part with the hole) because it is fairly easy to cause damage to the gold surface especially when using fine tipped tweezers. It is for that reason that we recommend the use of the SPI PTFE coated tweezers since they represent a more gentle means of aperture pick up with high precision tweezers. You have a choice of regular or self-closing high precision styles that are PTFE coated.

To prepare your work surface, where the apertures will be handled, first place one or two sheets of fine lens tissue, such as the SPI Lens Cleaning Tissue. Carefully cut the tape sealing the box (from the glass cover) with a new single edged razor blade. Next, with your fingers, carefully grip the cover glass and the box (white or black bottom) and invert them to get the cover glass facing down. Remove slowly the packaging box and the aperture can be gripped with fine PTFE coated tweezers, probably the most easily done with Style #5, directly from the cover glass. Be sure that when using such sharp and fine tweezers, only the edges of the aperture are ever touched. In any case, never, ever touch the gold surface with anything!

An alternative method is to remove the cover glass and invert the bottom part of the shipping case directly over an SPI lens cleaning tissue. For some workers, it is easier to grip the aperture with the fine tweezers when the lens cleaning tissue is the surface than if the glass top is the surface. We are being very specific also about the brand of the lens cleaning tissue, either the SPI or Ross brands are acceptable but not all lens cleaning tissues have such outstanding non-linting (and therefore non- contaminating) construction.

Information about use in the column:

When the apertures are being used under vacuum in an electron optical system, be sure it is removed from the optical axis if for any reason it is necessary to let air into the column.

Cleaning:

After several weeks of intensive use in an electron beam column, a small deposit could be formed on the aperture. Now since the aperture itself "runs" quite hot, and in essence is "self cleaning" anyhow, the rate of such deposit buildup is quite slow and by some, is never even observed. Clearly, the "dirtier" the column or the dirtier the samples (e.g. organics vs. metals), the more likely this kind of contamination can occur. But such contamination build up can very easily be removed, by the following procedure:

1) Focus the second condenser of the TEM.

2) Go to the diffraction position to give a clear image of the edge of the aperture.

3) By moving the aperture holder, the beam will clean the edges of the hole.

Clearly, one must be very careful at this point to not "burn a hole" or otherwise damage the aperture at this point. We want to stress that point because SPI Supplies will not replace any apertures damaged this way. But with some amount of practice, one can successfully clean apertures for continued use this way.

Under no circumstances can these gold foil thin film apertures be cleaned in a vacuum evaporator using high temperature as one would do for drilled Pt or Mo apertures.

Another method for cleaning dirty apertures apparently involves the use of the SPI Plasma Prep II Plasma Etcher using an oxygen plasma. The oxygen plasma will not react with the gold foil but will remove any contamination that has plated onto the aperture, assuming it is of course, carbonaceous and organic in nature.

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