An Efficient and Cost-Effective Method for Preparing Transmission Electron Microscopy Samples from Powders

Transmission electron microscopy sample preparation method for micrometer-sized powder particles using focused ion beam

A TEM sample preparation technique for micrometer-sized powder particles in the 1-10 μm size range is proposed, using a focused ion beam (FIB) system. It is useful for characterizing elemental distributions across an entire cross-section of a particle. It is a simple and universal method without using any embedding agent, enabling the powder particles with different size, shape or orientation to be easily selected based on the SEM observations. The suitable particle is covered with Pt coating layers through an ion-beam-assisted deposition. The Pt coating layers provide sufficient support for the TEM lamella. A small piece of tungsten needle is used as a support under the particle by taking a series of operations using a micromanipulator. The particle can be precisely thinned by the ion beam to be suitable for both TEM observation and EDX elemental mapping. This novel technique reduces the TEM sample preparation time to a few hours, allowing much higher efficiency compared to complicated and time-consuming embedding methods.

Novel Method for Preparing Transmission Electron Microscopy Samples of Micrometer-Sized Powder Particles by Using Focused Ion Beam

The preparation of transmission electron microscopy (TEM) samples from powders is quite difficult and challenging. For powders with particles in the 1-5 μm size range, it is especially difficult to select an adequate sample preparation technique. Epoxy is commonly used to bind powder, but drawbacks, such as differential milling originating from unequal milling rates between the epoxy and powder, remain. We propose a new, simple method for preparing TEM samples. This method is especially useful for powders with particles in the 1-5 μm size range that are vulnerable to oxidation. The method uses solder as an embedding agent together with focused ion beam (FIB) milling. The powder was embedded in low-temperature solder using a conventional hot-mounting instrument. Subsequently, FIB was used to fabricate thin TEM samples via the lift-out technique. The solder proved to be more effective than epoxy in producing thin TEM samples with large areas. The problem of differential milling was mitigated, and the solder binder was more stable than epoxy under an electron beam. This methodology can be applied for preparing TEM samples from various powders that are either vulnerable to oxidation or composed of high atomic number elements.