Focused Ion Beam Sample Preparation
In contrast to time-consuming conventional TEM-specimen preparation methods, the focused ion beam (FIB) sputtering in a dual beam SEM system allows to produce high-quality specimens for various TEM studies in a (semi-)automated and much quicker way (within several hours). Modern dual beam FIB/SEMs use precise piezo-controlled manipulators, various gas injection systems to protect the sample surface, energy dispersive X-ray spectroscopy to measure composition and different detectors to image the specimen during the preparation process. In the dual systems, the imaging process results from using scanning electrons (SEM) whereby scanning of focused gallium ions at the sample surface enables local material abrasion.
Helios Nanolab FIB
The standard TEM-lamella preparation (lift-out method) process consists of depositing a protective layer (e.g. Pt, C, W), cutting the slice perpendicular to the surface (cross-section preparation), lifting out of the slice with the help of a micromanipulator, attaching the specimen to a TEM support grid made of Cu or Mo, and finally polishing the lamella to the desired dimensions and thicknesses. Variations of both, the accelerating voltage (typically 5 – 30 keV) and beam current (2,8 nA – 48 pA) make the FIB/SEM systems able to prepare ultra-thin TEM-specimens from almost any materials in solid form ranging from metals to soft matter.
At the ER-C we work with a Helios NanoLab 400S and a Helios NanoLab 460F1.
The Fischione Nanomill® is a low-energy focused Ar ion (<1 keV) milling system dedicated for removal of the FIB-induced damage layer from TEM lamellae. The scanning ion beam provides images based on secondary electrons, which help to focus the sputtering process exclusively on the FIB-prepared lamella. The system is equipped with liquid nitrogen cooling dedicated for sputtering of sensitive materials. The parameters of the ion milling process can be individually fitted to the sample material and aim of the TEM experiment.