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Preparation of Thin Samples for viewing in a Transmission Electron Microscope

IP.com Disclosure Number: IPCOM000229926D
Publication Date: 2013-Aug-07
Document File: 1 page(s) / 37K

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Preparation of Thin Samples for viewing in a Transmission Electron Microscope

     Because a sample must be very thin for viewing with transmission electron microscopy (whether TEM or STEM, scanning transmission electron microscope), preparation of the sample can be delicate, time consuming work. One method of preparing a TEM sample is to cut the sample from a substrate using an ion beam. A probe is attached to the sample, which is moved away from the substrate from which it was extracted and typically attached to a TEM grid using ion beam FIB deposition or other method. The sample is thinned using the ion beam either before it is separated from the substrate, or after it is mounted in the grid.

     With the some automated TEM prep processes, a portion of the sample that does not include the region of interest will be thicker than the portion containing the region of interest and through which the electron beam will pass. The lamellae typically have a wedge shape in which the sample's surface (coated with FIB Tungsten) is relatively thick (70-80nm) and the thinned region decreases to about 50nm at about 500nm below the surface. This wedge shape limits the amount of thinning possible. As the sample is thinned further, the process creates a hole in the thinned region where the wedge is the thinnest.

     One technique to avoid this problem is to use a carbon overcoat, which is a closer match to the substrate's sputter removal rate and does not produce a wedge shape. However, this causes a problem because many users prefer an overcoat with a high Z-contrast for imaging insulative and non-conductive materials. Users must choose between an automated T...