Abstract
Automation changed the economics of TEM lamella preparation. It made the process faster, more repeatable, and less dependent on expert operators. But it did not solve everything. A lamella can be prepared automatically, meets the expected geometry and thickness, nevertheless, if prepared on a FIB-SEM with Ga-source, it still carry gallium-induced damage that limits what can be trusted in S/TEM analysis.
That was the remaining gap in TEM lamella preparation. AURA™ Gentle Ion Beam closes it by bringing low-energy argon polishing directly into the FIB-SEM workflow, so final cleaning becomes part of the same preparation process. The result is not just more lamellae, but lamellae that are cleaner, more repeatable, and more reliable for real analysis.
For years, Transmission Electron Microscopy (TEM) specimen preparation was defined by scarcity. Not of instruments, but of expertise. Preparing a high-quality lamella required skill, experience, and constant attention. Throughput was limited, and the process itself became a bottleneck for S/TEM analysis. Automation, such as TEM AutoPrep™ Pro, changed that paradigm. Integrated into Tescan AMBER™ and Tescan SOLARIS™, it enables workflows that once required constant attention from experienced operators to run autonomously, day or night, without supervision. A user can define a preparation workflow once and replicate it consistently across multiple samples. Lamellae can be prepared overnight, turning idle instrument time into productive throughput. In practical terms, this means one thing: the quantity of S/TEM specimens is no longer the limiting factor. Labs can produce more samples, more consistently, and without being constrained by operator availability. Even non-expert users, after minimal training, can prepare lamellae that closely match expert-level outputs by simply following predefined recipes.
Automation delivered what it promised. But it also exposed us to what it didn’t solve.
TEM AutoPrep™ Pro is excellent at automating the process. It is not designed to question whether that process produces the best possible result from any sample, especially if the sample interact with the Ga+ beam in unpredictable manner.
In TEM sample preparation, that distinction becomes critical. Interestingly, a lamella can meet all the expected parameters—correct thickness, correct geometry—and still fail in S/TEM. The reason lies in the physics of the preparation itself. Gallium-based FIB (Focused Ion Beam) milling, even when carefully controlled, introduces damage layers and implantation effects that can fundamentally alter the specimen. For thin lamellae (typically below 50 nm), this becomes a major issue. The damage layers created during Ga⁺ milling can represent a significant fraction (in some cases up to ~30 %) of the total thickness. In extreme cases, a large portion of the sample no longer carries meaningful structural information.
And the problem is even more pronounced in certain materials. Metals such as aluminium and copper, as well as compound semiconductors like GaN or GaAs, are particularly sensitive to gallium implantation. The result is not just reduced image quality, but visible artifacts that can directly affect data interpretation.
Automated TEM lamella preparation does not fix this. It simply reproduces it - consistently.
This is where AURA™ Gentle Ion Beam (GIB) comes into the picture. In materials science S/TEM specimen preparation community, the solution to gallium-induced damage has long been known: low-energy (~200 eV) argon (Ar⁺) ion beam cleaning. Unlike gallium, argon is chemically inert. It removes the damaged surface layer without introducing implantation or altering the material structure.
However, what has historically been missing is not the physics, but the practicality. Standalone argon systems placed next to your FIB-SEM introduce additional complexity. It requires sample transfer, setup, and careful handling at the most fragile stage of specimen preparation. This creates risks: contamination, misalignment, and even sample loss.
AURA™ addresses these challenges by bringing argon cleaning directly into the FIB-SEM chamber, and therefore into the TEM lamella preparation workflow.
The image shows the retractable AURA™ GIB integrated inside the chamber and aligned with the FIB-SEM coincidence point.
Instead of treating final polishing as a separate step, it becomes part of the TEM lamella preparation process itself. Ar+ cleaning, inspection, and verification all take place within a single system, under the same conditions and without breaking vacuum. The impact is straightforward but profound. Now, ultra-thin lamellae without significant Ga+ induced damage can be produced not only from standard materials, but also from those previously considered challenging or risky. Sensitive alloys, multi-phase materials, and Ga-reactive systems can be prepared without introducing the artifacts that would otherwise compromise the result.
TEM AutoPrep™ Pro already improves repeatability at the workflow level. It ensures that every preparation step is executed consistently. However, in some cases, repeating a workflow does not guarantee a repeatable outcome.
Final polishing, especially at energies of 1 keV and below, which is needed to avoid excessive damage of the Ga+ sensitive sample, has traditionally been one of the most operator-dependent steps in TEM preparation. Low-keV FIB-SEM finishing requires precise positioning of polishing rectangle, parameter optimization, and experience. Even small mistakes—such as incorrect placement of the polishing window—can lead to over-thinning or localized damage.
This is where AURA™ introduces another subtle but important shift.
Because the Argon beam is fully integrated and controlled through the same system, the process becomes easier to execute reliably. For many users, enabling the AURA™ polishing step is far more straightforward than manually optimizing sub-1 keV Ga⁺ polishing parameters and polishing rectangle positioning.
The complexity shifts from the user to the system. AURA™ reduces variability not only between expert and non-expert users, but also between shifts, sites, and even different types of samples. It transforms what was once a skill-dependent step into a controlled, repeatable part of the TEM lamella preparation workflow.
With TEM lamella full automation, EM industry solved the first challenge: how to produce more lamellae, more efficiently, and with less dependence on expert users. But it did not solve the more important question: are those lamellae consistently suitable for S/TEM analysis, regardless of the material l?
That requires something more. It requires preserving material integrity, eliminating artifacts, and ensuring that the final result, not just the process, is consistent and reliable.
And this is where AURA™ makes the difference.
By integrating argon Gentle Ion Beam polishing directly into the FIB-SEM, AURA™ extends TEM lamella automation beyond repetitive execution into reliable outcomes . It ensures that samples are not only thin, but also structurally intact. Not just reproducible in process, but consistent in quality.
And that is the difference between automated TEM lamella preparation and the next step. Automation helps you produce specimens, AURA™ helps you trust the results.
Petr Klimek, PhD
Product Marketing Director, Tescan