NanoMEGAS Precession Electron Diffraction

ASTAR: Orientation and Phase mapping

Automated orientation and phase mapping analysis of a variety of materials (metals, semiconductors, oxides etc.) by TEM using 4D-SPED technique consists of a successful application based on PED, called ASTAR. The major benefit of the technique is the high spatial resolution that can be down to 1-3 nm resolution (in case of FEG-TEM). Beam Precession is essential to improve data quality, in terms of dynamical effect reduction, and diffraction patterns increased resolution improving significantly the results reliability due to the present of higher order reflection. This application allows the user to further analyse their samples in nm scale, by Virtual Dark Field images, Texture analysis, Grain boundaries, Grain size distribution, etc

TopSPIN strain: Strain and Deformation analysis

The 4D-SPED acquisition method can also be applied to obtain strain mapping analysis (TopSPIN strain) of semiconductor materials at 1-4 nm resolution (sensitivity 0.02%), based on comparison of PED- patterns of strained areas with a reference (non-strained) area. The use of a precessing beam is essential for observing diffraction spots further away from the central spot, enhancing the strain sensitivity detection, and furthermore, improving any sample bending or thickness effect. Strain mapping analysis in TEM by 4D-SPED technique is a straightforward method that can be applied at any TEM and provides rapid and accurate data (same order of magnitude as dark field holography) without any requirement to index diffraction patterns, is critical to monitor the designed and unintended strain distributions.

TopSPIN strain-Features

• Strain analysis software for semiconductor materials and single crystal uniformly oriented systems.
• Strain sensitivity down to 0.1-0.01%
• Spatial resolution down to 1-5nm (TEM & sample depending)
• Precession: Facilitates the zone axis orientation of the sample, reduces the sensitivity of the sample thickness and bending effect, increase the number of higher order reflections, reduces dynamical scattering.

ADT-3D: PED tomography (Precession 3D-ED)

PED was firstly applied in electron crystallography, which in combination with 3D diffraction tomography (or 3D-ED, MicroED) in TEM, has become a critical method for structure determination of various nanocrystals, from minerals and alloys to complex zeolites, MOFs, organic compounds and proteins. In the conventional PED tomography method, a series of ED patterns are collected in a TEM every 1degree of tilting around the goniometer axis. Acquired data are automatically processed by specific software (ADT-3D). Specifically, the diffraction patterns are merged towards the reciprocal space 3D reconstruction, cell parameters determination, indexing and intensities measurement used for ab initio crystal structure determination .

ePDF basic: Amorphous Materials Characterisation

Precession electron diffraction in TEM is reported to provide high quality data for analysis of amorphous or nanocrystalline materials. Typical total scattering patterns are acquired in TEM in a few seconds, a speed only matched by synchrotron radiation (lab X-ray acquisition is a much more time-consuming approach for such materials (2-20 hours). The total scattering data are processed by a specific software (ePDF) using the well-known Pair Distribution Function method. Amorphous and/or nanocrystalline materials can not only be identified but furthermore can be characterised through the interatomic distances from the PDF diagram.

ePDF advanced: Amorphous Materials Mapping

The latest (introduced spring 2025) software expands the basic ePDF version to analyse 4D-SPED data, obtaining ePDF maps, which is particularly useful for studying amorphous, nanocrystalline, and disordered systems, with applications in semiconductor materials, amorphous glass, amorphous solid dispersions and polymers. The ePDF is automatically computed for every pixel/step of the electron diffraction data series. The computed ePDFs are used to determine the Pearson correlation function, enabling a rapid assessment of similarities and differences across the scanned area. Additionally, peak positions, widths, and heights of the ePDF profiles can be plotted as a function of the x-y position in the map to identify structural variations.

eEF mapping: Electric Field Studies

Detailed characterisation of local Electric Fields and built-in potentials in functional materials is NanoMEGAS’ recent application, combining 4D-SPED acquisition together with dedicated data processing software. During scanning over the sample, the transmitted beam is deflected by the local electric field (Coulomb force). The strength and direction of the local electric field translates into the shift of the intensity distribution in the transmitted central electron beam. Beam Precession is essential to get rid of dynamical effects which prevent accurate determination of the COM (Centre of Mass) and obtain ED patterns with less noise leading to enhanced results [5]. Electric field calculations are of high interest to study properties of many materials and devices, e.g. (P-N junctions, quantum wells, semiconductors, batteries, nanowires, etc)

A range of side entry camera mounts which optimise the signal quality from a stingray camera. This mechanism features faster decay phosphor, optimised optical coupling, special lens and reduced background light contamination. Additionally, the camera is mounted perpendicular to the image plane resulting in distortion free diffraction images. These are available for side entry ports (35mm) on most columns.