Nm-scale Resolution Research Articles

Scanning precession electron diffraction data analysis approaches for phase mapping of precipitates in aluminium alloys

Mapping the spatial distribution of crystal phases with nm-scale spatial resolution is an important characterisation task in studies of multi-phase materials. One popular approach is to use scanning precession electron diffraction which enables semi-automatic phase mapping at the nanoscale by collecting a single precession electron diffraction pattern at every probe position over regions spanning up to a few micrometers. For a successful phase mapping each diffraction pattern must be correctly identified. In this work four different approaches for phase mapping of embedded precipitates in an Al-Cu-Li alloy are compared on a sample containing three distinct crystal phases. These approaches are based on: non-negative matrix factorisation, vector matching, template matching and artificial neural networks. To evaluate the success of each approach a ground truth phase map was manually created from virtual images based on characteristic phase morphologies and compared with the deduced phase maps. The percentage accuracy of all methods when compared to the ground truth was satisfactory, with all approaches obtaining scores above 98%. The optimal method depends on the specific task at hand. Non-negative matrix factorisation is suitable with limited prior data knowledge but performs best with few unique diffraction patterns and requires substantial post-processing. It has the advantage of reducing the dimensionality of the dataset and handles weak diffracted intensities well given that they occur repeatedly. The current vector matching implementation is fast, simple, based only on the Bragg spot geometry and requires few parameters. It does however demand that each Bragg spot is accurately detected in each pattern and the current implementation is limited to zone axis patterns. Template matching handles a large range of orientations, including off-axis patterns. However, achieving successful and reliable results often require thorough data pre-processing and do require adequate diffraction simulations. For artificial neural networks a substantial setup effort is demanded but once trained it excels for routine tasks, offering fast predictions. The implemented codes and the data used are available open-source. These resources and the detailed assessment of the methods will allow others to make informed decisions when selecting a data analysis approach for 4D-STEM phase mapping tasks on other material systems.

Mapping of the Electrostatic Potentials in a Fully Processed Led Device with nm-Scale Resolution by In Situ off-Axis Electron Holography.

The optoelectronic properties of a fully processed red emitting AlGaInP micro-diode device is measured using standard I-V and luminescence measurements. A thin specimen is then prepared for in situ transmission electron microscopy analysis by focused ion beam milling, then the changes of electrostatic potential as a function of applied forward bias voltage are mapped by off-axis electron holography. We demonstrate that the quantum wells in the diode sit on a potential gradient until the threshold forward bias voltage for light emission is reached; at which point the quantum wells are aligned at the same potential. From simulations, a similar effect for the band structure can be demonstrated, where the quantum wells are aligned at the same energy level, and contain electrons and holes that are available for radiative recombination at this threshold voltage. We demonstrate that off-axis electron holography can be used to directly measure the potential distribution in optoelectronic devices, and is a powerful tool to help better understand their performance and to improve simulations.

Assessment of Active Dopants and p-n Junction Abruptness Using In Situ Biased 4D-STEM.

A key issue in the development of high-performance semiconductor devices is the ability to properly measure active dopants at the nanometer scale. In a p-n junction, the abruptness of the dopant profile around the metallurgical junction directly influences the electric field. Here, a contacted nominally symmetric and highly doped (NA = ND = 9 × 1018 cm-3) silicon p-n specimen is studied through in situ biased four-dimensional scanning transmission electron microscopy (4D-STEM). Measurements of electric field, built-in voltage, depletion region width, and charge density are combined with analytical equations and finite-element simulations in order to evaluate the quality of the junction interface. It is shown that all the junction parameters measured are compatible with a linearly graded junction. This hypothesis is also consistent with the evolution of the electric field with bias as well as off-axis electron holography data. These results demonstrate that in situ biased 4D-STEM can allow a better understanding of the electrostatics of semiconductor p-n junctions with nm-scale resolution.

Volume electron microscopy analysis reveals a new type of membrane junction required for mixing of parental genomes after fertilization

Imaging cells by light or fluorescence microscopy often provides great insights into mechanisms and dynamics of cellular processes. However, to gain information regarding the cellular structures that underlie these processes, nm‐scale resolution is often required. This type of resolution can be obtain using electron microscopy (EM). Traditionally, investigators imaged slices of chemically fixed cells or tissue in order to glimpse at relevant structures in 2‐dimensions. While powerful, this approach can potentially miss important information due to the somewhat random location of the planes analyzed, especially if a small number of images is a acquired. More recently, methodologies of volume EM have been developed that allow for sampling of a continuous volume at high resolution. Here we will describe how one such methodology, Focused Ion Beam‐ Scanning Electron Microscopy (FIB‐SEM), has been used to understand the process by which parental genomes mix after fertilization in C. elegans embryos. One‐cell embryos were collected during different stages of interphase and mitosis, fixed using high‐pressure freezing followed by freeze substitution, and stained to maximize membrane contrast. Images were acquired at 9 nm lateral (x,y) and axial (z) resolution, for volumes of approximately 10 X 10 X 25 µm3. These analyses revealed that for parental chromosomes to mix, the membranes of the two pronuclei must fused via a membrane structure that we termed “3‐way sheet junction”. The steps leading to the formation of 3‐way sheet junctions, and the more recent discovery of a novel membrane structure around centrosomes using these datasets, will be discussed.

Mapping of the electrostatic potentials in MOCVD and hybrid GaN tunnel junctions for InGaN/GaN blue emitting light emitting diodes by off-axis electron holography correlated with structural, chemical, and optoelectronic characterization

Off-axis electron holography has been used to measure the width of the depletion region in a series of tunnel junction GaN light emitting diodes that have been prepared using different growth processes for blue emission. The total measured potentials are combinations of the mean inner potential, dopant potential, and piezoelectric contributions. The dopant potential has been unmixed from the mean inner potential such that the width of the tunnel junctions in the different diodes can be measured. The experimental results are then compared to secondary ion mass spectrometry, simulations, and opto-electronic testing. We find that the measured tunnel junction widths are consistent with simulations as well as the current density and voltage characteristics. As such, off-axis electron holography has been demonstrated as a unique technique that can be used to reproducibly measure the electrostatic potentials in tunnel junctions with nm-scale resolution in real III–V device specimens.

Interferometric 4D-STEM for Lattice Distortion and Interlayer Spacing Measurements of Bilayer and Trilayer 2D Materials.

Van der Waals materials composed of stacks of individual atomic layershave attracted considerable attention due to their exotic electronic properties that can be altered by, e.g., manipulating the twist angle of bilayer materials or the stacking sequence of trilayer materials. To fully understand and control the unique properties of these few-layer materials, a technique that can provide information about their local in-plane structural deformations, twist direction, and out-of-plane structure is needed. In principle, interference in overlap regions of Bragg disks originating from separate layers of a material encodes 3D information about the relative positions of atoms in the corresponding layers. Here, an interferometric 4D scanning transmission electron microscopy technique is described that utilizes this phenomenon to extract precise structural information from few-layer materials with nm-scale resolution. It is demonstrated how this technique enables measurement of local pm-scale in-plane lattice distortions as well as twist direction and average interlayer spacings in bilayer and trilayer graphene, and therefore provides a means to better understand the interplay between electronic properties and precise structural arrangements of few-layer 2D materials.

Highly Nonuniform Ionic Transport on Ceramic-Polymer Hybrid Solid Electrolyte By Nanometer-Scale Operando Imaging

The ion conductivity of solid-state electrolytes (SSEs) has been greatly enhanced to a level comparable to that of liquid electrolytes, which is critical for fast charging/discharging. However, ion transport has primarily been characterized by macroscopic measurements such as electrochemical impedance spectroscopy (EIS) and galvanostatic profiles of charging/discharging. These measurements essentially reflect an average of microscopic ion-transport phenomena. Ion transport in SSEs can be far more complicated, but detailed microscopic transport characterization studies are currently lacking. Theoretical studies have proposed that ion transport can be governed by highly crystalline-orientation-dependent ionic hopping through the ceramic lattice, and some SSEs can even act as one-dimensional or two-dimensional ion conductors.[1] [2] Characterization methods are needed that measure in-situ ion transport with nm-scale spatial resolution to improve our understanding and tune the ion conduction in solid-state batteries (SSBs).Here, we report on nanometer-resolution in-situ ionic and electronic transport imaging of two advanced polymer-ceramic hybrid electrolytes: a polyimin/LixPySz (Li2S/P2S5:30/70) bulk hybrid SSE[3] and a Li-containing polyacrylonitrile (PAN)-coated Li-ion conductive glass ceramic (LICGC) with components of Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2.[4] Hybrid SSE is a promising approach that combines high ion conductivity of ceramic SSE and high stability of polymer SSE. We achieved the nm-resolution in-situ transport imaging by an atomic force microscopy (AFM)-based half-cell setup consisting of an AFM-probe/SSE/Li-metal structure (see Fig. 1). The AFM probe size ensures the nm-scale spatial resolutions, and we detected the small current in the pA‒fA (10-12‒10-15 A) range flowing through the AFM probe by using a logarithmic-scale current amplifier that detects both the ionic conduction and electronic leaking currents through the SSE.Concerning the bulk hybrid SSE, we found large ionic current fluctuations—five times to one order of magnitude on the LPS region of the SSE. The electronic leaking current is about 5 orders of magnitude smaller than the ionic current. Both the ionic and electronic transport at the LPS/polymer boundary show sharp transitions with no detectable current flowing through the polymer particles. The average ionic current through the LPS region decreases significantly with decreasing polyimine particle size and with extensive cycling, elucidating the Li-dendrite prevention mechanisms of this bulk hybrid SSE by polymer extension into ceramic interparticles.[3] The large ionic current fluctuation is understood in terms of highly anisotropic transport kinetic barriers along the different crystalline axes due to different grain orientations in the polycrystalline ceramic materials;[1] [2] this is a new factor to be mitigated to eliminate Li dendrite formation and growth in the SSBs.Regarding the polymer-coated LICGC SSE, we found significant ionic current fluctuation of 2‒3× the ion current but that is significantly less than in the LPS SSE. This mitigated current fluctuation is likely due to the more homogeneous ion-transport barriers of the glassy material with smaller grains in its amorphous matrix. The electronic leaking current is slightly larger than LPS, four orders of magnitude smaller than the ionic current. The polymer coating reduced the ionic current by several times compared with the bare LICGC SSE without the PAN coating. The PAN coating clearly prevented SSE degradation due to cycling.[4] Without the coating, the SSE after extensive cycling degraded extensively and nonuniformly, with domain sizes of μm to hundreds of μm. The degradation can be ionic blocking with slight electronic leaking as well as highly electronic shunting, depending on different domains or areas. The polymer coating effectively prevented both ionic and electronic degradation. In fact, ionic conduction improved by about 5 times, but electronic leaking was degraded slightly.Our AFM-based imaging opens up novel characterization of ionic and electronic transport in SSEs. The nm-scale inhomogeneous transport mechanisms as revealed by this operando imaging are far beyond the averaged results provided by macroscopic characterizations.

Determination of the internal piezoelectric potentials and indium concentration in InGaN based quantum wells grown on relaxed InGaN pseudo-substrates by off-axis electron holography

Micro light emitting diodes have been grown by metal organic vapor phase epitaxy on standard GaN and partly relaxed InGaNOS substrates with the purpose of incorporating higher concentrations of indium for identical growth conditions. Green emission has been demonstrated at wavelengths of 500 nm for the GaN template and 525 and 549 nm for the InGaNOS substrates, respectively. The structure, deformation, indium concentration and piezoelectric potentials have been measured with nm-scale spatial resolution in the same specimens by transmission electron microscopy. We show by off-axis electron holography that the piezoelectric potential and information about the indium concentration from the mean inner potential are obtained simultaneously. By separating the components using a model, we show that for higher concentrations of indium in the quantum wells (QWs) grown on InGaNOS substrates, the piezoelectric potentials are reduced. The measurements of the indium concentrations by electron holography have been verified by combining energy dispersive x-ray spectrometry, x-ray diffraction and from the tensile deformation made by precession electron diffraction. A discussion of the limitations of these advanced aberration-corrected transmission electron microscopy techniques when applied to nm-scale QW structures is given.

A Correlative ToF-SIMS/SPM Methodology for Probing 3D Devices.

With the continuous miniaturization and increasing complexity of the devices used in nanotechnology, there is a pressing need for characterization techniques with nm-scale 3D-spatial resolution. Unfortunately, techniques like Secondary Ion Mass Spectrometry (SIMS) fail to reach the required lateral resolution. For this reason, new concepts and approaches, including the combination of different complementary techniques, have been developed in over the past years to try to overcome some of the challenges. Beyond the problem of spatial resolution in a 3D SIMS experiment, one is also faced with the impact of changes in topography during the analysis. These are quite difficult to identify because they originate from the different sputter rates of the various materials and or phases in a heterogeneous system and are notorious at the interfaces between organic and inorganic layers. As each of these materials will erode at a different velocity, accurate 3D-analysis will require means to establish a spatially resolved relation between ion bombardment time and depth. Inevitably such a nonhomogeneous erosion will lead to the development of surface topography. The impact of these effects can be overcome provided one can capture the time and spatially dependent surface erosion (velocity) with high spatial resolution during the course of a profiling experiment. Incorporating a Scanning Probe Microscope (SPM) unit which provides topography measurements with high spatial resolution, into a SIMS tool (e.g., Time of Flight (ToF) SIMS) with means to alternate between SPM and SIMS measurements, is one approach to meet that demand for complementary topographical information allowing accurate 3D chemical imaging. In this paper, the result of integrating a SPM module into a ToF-SIMS system is presented illustrating the improvements in 3D data accuracy which can be obtained when analyzing complex 3D-systems.

From 2D STXM to 3D Imaging: Soft X-ray Laminography of Thin Specimens

X-ray tomography has become an indispensable tool for studying complex 3D interior structures with high spatial resolution. Three-dimensional imaging using soft X-rays offers powerful contrast mechanisms but has seen limited success with tomography due to the restrictions imposed by the much lower energy of the probe beam. The generalized geometry of laminography, characterized by a tilted axis of rotation, provides nm-scale 3D resolution for the investigation of extended (mm range) but thin (μm to nm) samples that are well suited to soft X-ray studies. This work reports on the implementation of soft X-ray laminography (SoXL) at the scanning transmission X-ray spectromicroscope of the PolLux beamline at the Swiss Light Source, Paul Scherrer Institut, which enables 3D imaging of extended specimens from 270 to 1500 eV. Soft X-ray imaging provides contrast mechanisms for both chemical sensitivity to molecular bonds and oxidation states and magnetic dichroism due to the much stronger attenuation of X-rays in this energy range. The presented examples of applications range from functionalized nanomaterials to biological photonic crystals and sophisticated nanoscaled magnetic domain patterns, thus illustrating the wide fields of research that can benefit from SoXL.

Characterization technique for detection of atom-size crystalline defects and strains using two-dimensional fast-Fourier-transform sampling Moiré method

Recently, we have developed a two-dimensional (2D) fast-Fourier-transform (FFT) sampling Moiré technique to visually and quantitatively determine the locations of minute defects in a transmission electron microscopy (TEM) image. We applied this technique for defect detection with GaN high electron mobility transistor (HEMT) devices, and successfully and clearly visualized atom-size defects in AlGaN/GaN crystalline structures. The defect density obtained in the AlGaN/GaN structures is ∼1013 counts/cm2. In addition, we have successfully confirmed that the distribution and number of defects closely depend on the process conditions. Thus, this technique is quite useful for a device development. Moreover, the strain fields in an AlGaN/GaN crystal were effectively calculated with nm-scale resolution using this method. We also demonstrated that this sampling Moiré technique is applicable to silicon devices, which have principal directions different from those of AlGaN/GaN crystals. As a result, we believe that the 2D FFT sampling Moiré method has great potential applications to the discovery of new as yet unknown phenomena occurring between the characteristics of a crystalline material and device performance.

A small protein probe for correlated microscopy of endogenous proteins

Probes are essential to visualize proteins in their cellular environment, both using light microscopy as well as electron microscopy (EM). Correlated light microscopy and electron microscopy (CLEM) requires probes that can be imaged simultaneously by both optical and electron-dense signals. Existing combinatorial probes often have impaired efficiency, need ectopic expression as a fusion protein, or do not target endogenous proteins. Here, we present FLIPPER-bodies to label endogenous proteins for CLEM. Fluorescent Indicator and Peroxidase for Precipitation with EM Resolution (FLIPPER), the combination of a fluorescent protein and a peroxidase, is fused to a nanobody against a target of interest. The modular nature of these probes allows an easy exchange of components to change its target or color. A general FLIPPER-body targeting GFP highlights histone2B-GFP both in fluorescence and in EM. Similarly, endogenous EGF receptors and HER2 are visualized at nm-scale resolution in ultrastructural context. The small and flexible FLIPPER-body outperforms IgG-based immuno-labeling, likely by better reaching the epitopes. Given the modular domains and possibilities of nanobody generation for other targets, FLIPPER-bodies have high potential to become a universal tool to identify proteins in immuno-CLEM with increased sensitivity compared to current approaches.

Off-axis electron holography for the measurement of active dopants in silicon semiconductor devices

There is a need in the semiconductor industry for a dopant profiling technique with nm-scale resolution. Here we demonstrate that off-axis electron holography can be used to provide maps of the electrostatic potential in semiconductor devices with nm-scale resolution. In this paper we will discuss issues regarding the spatial resolution and precision of the technique. Then we will discuss problems with specimen preparation and how this affects the accuracy of the measurements of the potentials. Finally we show results from experimental off-axis electron holography applied to nMOS and pMOS CMOS devices grown on bulk silicon and silicon- on-insulator type devices and present solutions to common problems that are encountered when examining these types of devices.

Strain mapping of semiconductor specimens with nm-scale resolution in a transmission electron microscope

The last few years have seen a great deal of progress in the development of transmission electron microscopy based techniques for strain mapping. New techniques have appeared such as dark field electron holography and nanobeam diffraction and better known ones such as geometrical phase analysis have been improved by using aberration corrected ultra-stable modern electron microscopes. In this paper we apply dark field electron holography, the geometrical phase analysis of high angle annular dark field scanning transmission electron microscopy images, nanobeam diffraction and precession diffraction, all performed at the state-of-the-art to five different types of semiconductor samples. These include a simple calibration structure comprising 10-nm-thick SiGe layers to benchmark the techniques. A SiGe recessed source and drain device has been examined in order to test their capabilities on 2D structures. Devices that have been strained using a nitride stressor have been examined to test the sensitivity of the different techniques when applied to systems containing low values of deformation. To test the techniques on modern semiconductors, an electrically tested device grown on a SOI wafer has been examined. Finally a GaN/AlN superlattice was tested in order to assess the different methods of measuring deformation on specimens that do not have a perfect crystalline structure. The different deformation mapping techniques have been compared to one another and the strengths and weaknesses of each are discussed.

Quantitative voxel-to-voxel comparison of TriBeam and DCT strontium titanate three-dimensional data sets

Recently, techniques for the acquisition of three-dimensional tomographic and four-dimensional time-resolved data sets have emerged, allowing for the analysis of mm3 volumes of material with nm-scale resolution. The ability to merge multi-modal data sets acquired via multiple techniques for the quantitative analysis of structure, chemistry and phase information is still a significant challenge. Large three-dimensional data sets have been acquired by time-resolved diffraction contrast tomography (DCT) and a new TriBeam tomography technique with high spatial resolution to address grain growth in strontium titanate. A methodology for combining three-dimensional tomographic data has been developed. Algorithms for the alignment of orientation reference frames, unification of sampling grids and automated grain matching have been integrated, and the resulting merged data set permits the simultaneous analysis of all tomographic data on a voxel-by-voxel and grain-by-grain basis. Quantitative analysis of merged data sets collected using DCT and TriBeam tomography shows that the spatial resolution of the DCT technique is limited near grain boundaries and the sample edge, resolving grains down to 10 µm diameter for the reconstruction method used. While the TriBeam technique allows for higher-resolution analysis of boundary plane location, it is a destructive tomography approach and can only be employed at the conclusion of a four-dimensional experiment.

In-Situ Electrochemical Microscopy of PEM Fuel Cell Materials

High-resolution imaging of the structural changes to Pt-based catalyst nanoparticles supported on carbon blacks using in-situ electrochemical liquid cell transmission electron microscopy (TEM) are being correlated with the behavior of similar materials incorporated in membrane electrode assemblies (MEAs) subjected to accelerated stress tests (ASTs), to elucidate catalyst and catalyst-support degradation phenomena contributing to fuel cell performance loss. Specialized in-situ holders for the TEM have been developed that incorporate patterned electrodes within a closed liquid flow cell that enable the interactions between catalyst particles and their supports to be imaged during potential cycling in relevant liquid electrolytes, such that the critical stages of materials corrosion during fuel cell operation can be imaged in real time at nm-scale resolution. The direct TEM observations of the changes to the catalyst (Pt dissolution and particle growth/coalescence) and carbon supports (mechanisms of progressive support corrosion) during in-situ electrochemistry, combined with the post-mortem evaluation of cathode layers comprised of similar Pt/C materials after AST of MEAs, provide an unprecedented means by which to “capture” catalyst and catalyst-support degradation mechanisms such that materials optimization strategies can be implemented to enhance fuel cell durability. Research sponsored by (1) the Office of Fuel Cells Technologies, Office of Energy Efficiency and Renewable Energy, the U.S. Department of Energy and (2) ORNL’s Center for Nanophase Materials Sciences, Scientific User Facilities Division, Office of Basic Energy Sciences, the U.S. Department of Energy.

Fabrication of 10 nm-Scale Complex 3D Nanopatterns with Multiple Shapes and Components by Secondary Sputtering Phenomenon

We introduce an advanced ultrahigh-resolution (∼ 15 nm) patterning technique that enables the fabrication of various 3D high aspect ratio multicomponents/shaped nanostructures. This methodology utilizes the repetitive secondary sputtering phenomenon under etching plasma conditions and prepatterned fabrication control. The secondary sputtering phenomenon repetitively generates an angular distribution of target particles during ion-bombardment. This method, advanced repetitive secondary sputtering lithography, provides many strategies to fabricate complex continuous patterns and multilayer/material patterns with 10 nm-scale resolution. To demonstrate the versatility of this method, we show induced vertical alignment of liquid crystals (LCs) on indium-tin-oxide (ITO) grid patterns without any alignment layers. The ITO grid pattern fabricated in this method is found to have not only an alignment capability but also electrode properties without electrical or optical damage.

Combinatorial Polarized TIRF-AFM Study of Membrane Reorganization by Alpha-Synuclein and Human Prion Protein

Many neurodegenerative diseases are caused by aggregation or fibrillation of membrane-associated proteins. Alpha-Synuclein (aS) is associated with Parkinson's Disease as a major component of Lewy bodies, and misfolded aggregates of human Prion Protein (PrP) are associated with spongiform encephalopathies. Here we study the influence of these proteins on the organization and topography of canonical raft-mimetic supported lipid bilayers (DSPC/DOPC/cholesterol at 35/35/30 mol% on mica) using a correlated polarized Total Internal Reflectance Fluorescence-Atomic Force Microscopy (pTIRF-AFM) platform. pTIRF allows for high-speed measurements of dynamic processes at diffraction-limited spatial resolution, while AFM gives time-averaged nm-scale spatial resolution. Using pTIRF and an oriented lipophilic dye (DiI-C18) we determine the local order in the membrane by measuring the ratio of fluorescence parallel and perpendicular to the membrane plane, while simultaneously measuring membrane topography using AFM. Upon addition of aS to our phase-segregated membrane system, liquid-ordered and liquid-disordered domains were mixed and the local order increased such that lipid headgroups were oriented more parallel to the membrane plane. Moreover, AFM topography revealed the formation of long, closed-loop tubules. Addition of the active segment PrP(106-126) to these raft-mimetic membranes resulted in a similar mixing of domains and an increase of local order, while AFM revealed the formation of peptide fibrils in and around cholesterol-rich domains. This study provides direct evidence of membrane reorganization and restructuring by aS and PrP, and the effect of membrane chemistry on aS and PrP self-association. These results portend future detailed investigations into the molecular-level factors responsible for these effects.

Experimental measurement of surface strains and local lattice rotations combined with 3D microstructure reconstruction from deformed polycrystalline ensembles at the micro-scale

AbstractThis article describes a new approach to characterize the deformation response of polycrystalline metals using a combination of novel micro-scale experimental methodologies. An in-situ scanning electron microscope (SEM)-based tension testing system was used to deform micro-scale polycrystalline samples to modest and moderate plastic strains. These tests included measurement of the local displacement field with nm-scale resolution at the sample surface. After testing, focused ion beam serial sectioning experiments that incorporated electron backscatter diffraction mapping were performed to characterize both the internal 3D grain structure and local lattice rotations that developed within the deformed micro-scale test samples. This combination of experiments enables the local surface displacements and internal lattice rotations to be directly correlated with the underlying 3D polycrystalline microstructure, and such information can be used to validate and guide further development of modeling and simulation methods that predict the local plastic deformation response of polycrystalline ensembles.

Field mapping of focused ion beam prepared semiconductor devices by off-axis and dark field electron holography

Off-axis electron holography is a unique technique in that it can be used to provide maps of the electrostatic potentials and strain in semiconductor specimens with nm-scale resolution. In this paper, we show that if sufficient care is taken, focused ion beam milling can be used to prepare electrically tested devices from a precise location on a wafer for studies of their electrostatic and strain fields as well as their structure and composition. We have compared the physical properties of several devices with process simulations and electrical test results which were measured over a time period of several months. We believe that electron holography can now be used to measure the positions of the electrical junctions and also quantitative values of the strain in an industrial environment.