Efficient Data Sampling Scheme to Reduce Acquisition Time in Statistical ALCHEMI.

The distribution of dopants in host crystals significantly influences the chemical and electronic properties of materials. Therefore, determining this distribution is crucial for optimizing material performance. The previously developed statistical ALCHEMI (St-ALCHEMI), an extension of the atom-location by channeling-enhanced microanalysis (ALCHEMI) technique, utilizes variations in electron channeling based on the beam direction relative to the crystal orientation.

Improved Dopant Fraction Variance Estimation in Statistical ALCHEMI Based on Correct Error Propagation Rule.

This report revisits the statistical atom location by channeling enhanced microanalysis (St-ALCHEMI) method, correcting the dopant site occupancy error by applying an appropriate error propagation rule. A revised equation for calculating the uncertainty in the determined dopant fractions is proposed. The revised equation is expected to correct the uncertainty in the determined dopant fractions, which is particularly significant in cases of low dopant concentrations and variable dopant occupancies across inequivalent host atomic sites.

Automating ALCHEMI at the nano-scale using software compatible with PC-controlled transmission electron microscopy.

Atom location by channeling-enhanced microanalysis (ALCHEMI) is a technique to obtain atom-site-specific information on constituent elements in a crystalline sample by acquiring a set of core electron transition spectra while tilting the incident beam. This methodology has been extended to a more quantitative technique called high-angular-resolution electron-channeled X-ray/electron spectroscopy (HARECXS/HARECES). There is a growing demand for analyzing smaller areas, such as small particles and multilayers.

Atomic-Scale Electrical Field Mapping of Hexagonal Boron Nitride Defects.

The distribution of electric fields in hexagonal boron nitride is mapped down to the atomic level inside a scanning transmission electron microscope by using the recently introduced technique of differential phase contrast imaging. The maps are calculated and displayed in real time, along with conventional annular dark-field images, through the use of custom-developed hardware and software. An increased electric field is observed around boron monovacancies and subsequently mapped and measured relative to the perfect lattice.

Direct observation of curvature of the wave surface in transmission electron microscope using transport intensity equation.

In optics it is well known that the image surface is curved, even when an illumination is an ideal plane wave. However, in transmission electron microscopy (TEM) the curvature of field, or wave surface, has not been discussed seriously. We have observed the curvature of field in TEM using the transport of intensity equation (TIE).

Managing dose-, damage- and data-rates in multi-frame spectrum-imaging.

As an instrument, the scanning transmission electron microscope is unique in being able to simultaneously explore both local structural and chemical variations in materials at the atomic scale. This is made possible as both types of data are acquired serially, originating simultaneously from sample interactions with a sharply focused electron probe. Unfortunately, such scanned data can be distorted by environmental factors, though recently fast-scanned multi-frame imaging approaches have been shown to mitigate these effects.

Boundary-artifact-free determination of potential distribution from differential phase contrast signals.

The differential phase contrast (DPC) imaging in STEM was mainly used for a study of magnetic material in a medium resolution. An ideal DPC signals give the center of mass of the diffraction pattern, which is proportional to an electric field. Recently, the possibility of the DPC imaging at atomic resolution was demonstrated.

STEM moiré analysis for 2D strain measurements.

A moiré pattern is created in a scanning transmission electron microscope (STEM) when the scan step is close to a crystalline periodicity. Usually, fringes are visible in only one direction, corresponding to a single set of lattice planes, but fringes can be formed in two directions or more. Using an accurate independent calibration, the strains in silicon devices have been determined from the spacing and orientation of one-directional STEM moiré fringes.