arXiv subjects

Sebastian Eich

Publications and source records attributed to Sebastian Eich.

3 recordsLinked to original sources

arXiv2026

MicroCup: A Cryogenic Specimen Preparation Strategy for Atom Probe Tomography of Organic Molecular Liquids

Atom probe tomography (APT) of organic molecular liquids is limited by poorly reproducible specimen geometry, reduced milling rates, and beam sensitivity during cryo-FIB preparation. Here we introduce a MicroCup strategy that confines liquids in a FIB-prepared nanoscale cavity prior to phase separation, reduces deposited volume to increase preparation throughput, enables reproducible specimen geometry, and minimizes beam exposure in the region of interest. Using the liquid crystals 4'-octyl-4-cyanobiphenyl (8CB) and 4'-octyloxy-4-cyanobiphenyl (8OCB) as model systems, we establish stable and reproducible field evaporation conditions, enabling the detected intact ion molecular preservation above 70% in smectic-like phases with interpretable fragmentation behavior. Comparative analysis further shows that the oxygen atom in 8OCB promotes preferential cleavage pathways associated with bond polarization under high electric fields. By inducing partial crystallization within the MicroCup cavity, distinct regions could be resolved: 8CB shows broadly similar evaporation behavior across crystalline and amorphous regions, whereas 8OCB exhibits clearer regional contrast, with smectic-like regions dominated by intact molecular or large fragments and crystalline domains producing small alkyl fragments and ether-type species. These results provide spatially resolved evidence of a solid-liquid interface in a freeze-prepared organic liquid by APT and establish a reproducible workflow for probing local phase behavior in soft materials.

cond-mat.mtrl-sci↗

arXiv2025

Revealing Nanoscale Molecular Organization in Liquid Crystals via Cryogenic Atom Probe Tomography

While liquid crystals (LCs) have been extensively studied, obtaining a comprehensive nanoscale picture of their molecular organization remains challenging, as conventional techniques face an intrinsic trade-off between spatial and chemical resolution. Here, cryogenic atom probe tomography (cryo-APT) is introduced as a new analytical approach for LC materials, using 4'-Pentyl-4-cyanobiphenyl (5CB) and 4'-Octyl-4-cyanobiphenyl (8CB) as representative model compounds. This was enabled by a tailored cryogenic focused ion beam (cryo-FIB) protocol optimized for small organic molecules. The method enables controlled field evaporation of both intact molecules and diagnostic fragments, achieving over 90% molecular retention while preserving four characteristic dissociation patterns. By spatially correlating these fragmentation profiles with the local electric field derived from the tip geometry, we reveal field-directed dissociation pathways of CB molecules. In parallel, the distribution of intact molecular ions enables nanoscale visualization of material structure: we resolve homogeneous mixing of 5CB and 8CB in the nematic phase and directly observe the sub-nanometer crystalline layering in a supercooled 8CB sample, with contrast to the surrounding amorphous matrix suggesting the presence of a solid-liquid interface. This work establishes cryo-APT as a new powerful analytical platform for LC research and reveals its broad potential for application in soft matter systems.

cond-mat.mtrl-sci↗

arXiv2021

The modular Atom Probe Concept

Atomic probe tomography (APT), based on the work of Erwin Mueller, is able to generate three-dimensional chemical maps in atomic resolution. The required instruments for APT have evolved over the last 20 years from an experimental to an established method of materials analysis. Here, we describe the realization of a new instrument concept that allows the direct attachment of APT to a dual beam SEM microscope with the main achievement of fast and direct sample transfer. New operational modes are enabled regarding sample geometry, alignment of tips and microelectrode. The instrument is optimized to handle cryo-samples at all stages of preparation and storage. The instrument comes with its own software for evaluation and reconstruction. The performance in terms of mass resolution, aperture angle, and detection efficiency is demonstrated with a few application examples.

physics.ins-det↗