Many-beam dynamical simulation of electron backscatter diffraction patterns

Winkelmann, Aimo; Trager-Cowan, C.; Sweeney, F.; Day, A. P.; Parbrook, P. J.

doi:10.1016/j.ultramic.2006.10.006

Cited by 176 publications

(168 citation statements)

References 29 publications

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“…Each electron's contribution to the EBSD pattern was simulated, using the calculated image intensity as a probability distribution function, which also provides the Poisson contribution to the noise. The input image intensity was simulated using dynamical diffraction calculations of the Kikuchi band features in EBSD patterns using code developed by Winkelmann [34]. The patterns simulated using this model for the detector geometry, SEM imaging conditions, and for an electron budget corresponding to our experimental data are shown in Fig.…”

Section: H Y S I C a L R E V I E W L E T T E R S Week Ending 9 Augustmentioning

confidence: 99%

Direct Detection of Electron Backscatter Diffraction Patterns

et al. 2013

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We report the first use of direct detection for recording electron backscatter diffraction patterns. We demonstrate the following advantages of direct detection: the resolution in the patterns is such that higher order features are visible; patterns can be recorded at beam energies below those at which conventional detectors usefully operate; high precision in cross-correlation based pattern shift measurements needed for high resolution electron backscatter diffraction strain mapping can be obtained. We also show that the physics underlying direct detection is sufficiently well understood at low primary electron energies such that simulated patterns can be generated to verify our experimental data. DOI: 10.1103/PhysRevLett.111.065506 PACS numbers: 61.05.JÀ, 07.78.+s, 68.37.Hk Electron backscatter diffraction (EBSD) is a scanning electron microscope (SEM) based method in which diffraction of low-energy-loss electrons as they exit through the topmost few tens of nanometers leads to Kikuchi diffraction. In most EBSD studies the incident electron beam is stepped across a grid of points on the sample surface and the EBSD patterns analyzed in an automated way to determine crystal phase, orientation, or lattice strain variation. The EBSD method has evolved rapidly over the last two decades [1][2][3][4][5]. Most research has been directed to the application of this versatile tool to an ever increasing array of problems in materials characterization but the analysis methods themselves have also advanced, notably in three dimensional imaging using focused ion beam (FIB)-SEM [6-9] and in strain mapping [10][11][12][13][14]. However, the detector technology used to record EBSD patterns has essentially remained unchanged for over a decade and now limits performance in several application areas, such as strain resolution and low dose mapping, and prevents the development of new areas.The earliest EBSD patterns were recorded on film either exposed directly to the electrons in the chamber [15][16][17], or indirectly imaging a phosphor screen using a camera outside the vacuum [18]. Subsequently, these were replaced by various image intensified cameras giving the convenience of a live image of the pattern at the scintillator but with degraded pattern quality compared to that recorded using film [19]. Subsequently, scintillator coupled CCDs were introduced in the early 1990s [20,21]. In a limited number of examples tapered fiber-optic bundles have been used to couple the CCD to the scintillator with good results [20] but the alternative optical lens coupling has been adopted in the vast majority (> 95%) of instruments currently in use. Departures from these detection schemes have included an investigation of microchannel plates [22] and the adoption of a retarding electrostatic field for energy filtering [23].In other fields there have been significant advances in detectors directly exposed to the imaging beam for the detection of x rays [24,25] and medium energy electrons [26][27][28][29]. The current development of TEM instr...

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Section: H Y S I C a L R E V I E W L E T T E R S Week Ending 9 Augustmentioning

confidence: 99%

Direct Detection of Electron Backscatter Diffraction Patterns

et al. 2013

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“…For each orientation, the process consists of three steps. The first step models the interaction of the electron beam with the sample using the Schrödinger equation with a Bloch wave ansatz [11]. The backscattered electron yield is calculated for a set of directions covering the hemisphere of all possible exit directions.…”

Section: Construction Of Diffraction Pattern Dictionarymentioning

confidence: 99%

EBSD image segmentation using a physics-based forward model

Park

Wei

Graef

et al. 2013

2013 IEEE International Conference on Image Processing

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We propose a segmentation and anomaly detection method for electron backscatter diffraction (EBSD) images. In contrast to conventional methods that require Euler angles to be extracted from diffraction patterns, the proposed method operates on the patterns directly. We use a forward model implemented as a dictionary of diffraction patterns generated by a detailed physics-based simulation of EBSD. The combination of full diffraction patterns and a dictionary allows anomalies to be detected at the same time as grains are segmented, and also increases robustness to noise and instrument blur. The proposed method is demonstrated on a sample of the Ni-base alloy IN100.

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“…We used the Nelder-Mead simplex method 25 to find the local maximum of the cross-correlation coefficient between experiment and simulations, with start parameters near an orientation obtained by a conventional indexing procedure based on the Hough transform. 26 For the dynamical electron diffraction simulations 27 and the best-fit optimizations, we applied the software ESPRIT DynamicS (Bruker Nano, Berlin). In the optimization procedure, the simulated Kikuchi patterns are reprojected from stored master data according to the current values of the projection parameters, then the crosscorrelation coefficient is calculated, and new updated projection parameters are chosen for the next iteration according to the simplex approach.…”

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Diffractive triangulation of radiative point sources

Vespucci

Naresh-Kumar

Trager-Cowan

et al. 2017

Applied Physics Letters

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We describe a general method to determine the location of a point source of waves relative to a two-dimensional single-crystalline active pixel detector. Based on the inherent structural sensitivity of crystalline sensor materials, characteristic detector diffraction patterns can be used to triangulate the location of a wave emitter. The principle described here can be applied to various types of waves provided that the detector elements are suitably structured. As a prototypical practical application of the general detection principle, a digital hybrid pixel detector is used to localize a source of electrons for Kikuchi diffraction pattern measurements in the scanning electron microscope. This approach provides a promising alternative method to calibrate Kikuchi patterns for accurate measurements of microstructural crystal orientations, strains, and phase distributions

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Many-beam dynamical simulation of electron backscatter diffraction patterns

Cited by 176 publications

References 29 publications

Direct Detection of Electron Backscatter Diffraction Patterns

Direct Detection of Electron Backscatter Diffraction Patterns

EBSD image segmentation using a physics-based forward model

Diffractive triangulation of radiative point sources

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