Laser-based sample preparation for high-resolution X-ray-computed tomography of glasses and glass ceramics.

X-ray-computed tomography with sub-micron resolution (nano-CT) is one of the most useful techniques to examine the 3D microstructure of materials down to voxel sizes 10 nm. However, since size and shape of samples have considerable influence on acquisition time and data quality, adapted and universally applicable workflows are needed. Three novel workflows for sample preparation using ultra-short pulsed lasers are presented which allow for reproducible fabrication, safe extraction and mounting of samples. Their application potential is illustrated via nano-CT measurements of glass ceramics as well as a laser-modified glass. Since the according sample geometries take also the requirements of other analytical techniques such as transmission electron microscopy into account, samples prepared according to the new workflows can be furthermore seen as a starting point for correlative microstructural analyses involving multiple techniques.

Efficient preparation of microtip arrays for atom probe tomography using fs-laser processing.

Microtip arrays, also called microtip coupons, are routinely used in atom probe tomography (APT) as specimen carriers. They are commercially available consumables, usually made of Si with high electrical conductivity, produced via dedicated shaping techniques. Their purpose is to act as a specimen mount after focused ion beam (FIB) based lift-out procedures. Within this work, an alternative approach to prefabricated microtip coupons is presented, by directly creating a microtip array on the sample to be investigated utilizing fs-laser processing. An exemplary array of microtip posts was fs-laser processed from a TiN coating on Si substrate and subjected to final preparation via annular FIB milling. Subsequently, APT specimen of the TiN coating as well as of the Si substrate were successfully measured in laser assisted mode, using a commercial local electrode APT system. To further emphasize the versatility of the proposed approach, additional voltage measurements of highly conductive B doped Si arrays as well as exemplarily fs-laser processed microtip arrays of various other materials are provided as supplementary material to this article. The presented methodology bypasses the lift-out and avoids the necessity of a Pt weld between specimens and coupon posts which is frequently considered to represent a weak spot. It reduces consumables consumption and provides a high number of specimens in short time, while it is applicable for a wide range of materials and has thus the potential to revolutionize APT specimen preparation.