Transmission Kikuchi diffraction in a scanning electron microscope: A review

Sneddon, Glenn; Trimby, Patrick; Cairney, Julie M.

doi:10.1016/j.mser.2016.10.001

Cited by 149 publications

(81 citation statements)

References 95 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Due to the small size of the MgB 2 grains, it turned out that the newly developed transmission EBSD (t‐EBSD) technique is better suited for the investigation of such samples, enabling a higher spatial resolution and being less influenced by charging effects etc. (Keller & Geiss, ; Trimby, ; Sneddon et al ., ). On MgB 2 , the average grain misorientation and the grain boundary lengths could directly be measured (Koblischka‐Veneva et al ., ), proving the importance of the grain boundaries (GBs) for flux pinning.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the microstructure of bulk MgB₂ using TEM, EBSD and t‐EBSD

Koblischka-Veneva

Koblischka

Schmauch

et al. 2019

Journal of Microscopy

View full text Add to dashboard Cite

Summary EBSD analysis can provide information about grain orientation, texture and grain boundary misorientation of bulk superconducting MgB2 samples intended for supermagnet applications. However, as the grain size of the MgB2 bulks is preferably in the 100–200 nm range, the common EBSD technique operating in reflection mode works only properly on highly dense samples. In order to achieve reasonably good Kikuchi pattern quality on all types of MgB2 samples, we apply here the newly developed transmission EBSD (t‐EBSD) technique to spark‐plasma sintered MgB2 samples. This method requires the preparation of TEM slices by means of focused ion‐beam milling, which are then analysed within the SEM, operating with a custom‐built sample holder. To obtain multiphase scans, we identified the Kikuchi pattern of the MgB4 phase which appears at higher reaction temperatures and may act as additional flux pinning sites. We present here for the first time EBSD mappings of multiple phases, which include MgB2, MgB4 and MgO. Lay Description The electron backscatter diffraction (EBSD) technique operating in the scanning electron microscope provides information on the crystallographic orientation the material by recording Kikuchi patterns. In polycrystalline samples, it becomes possible to analyse the orientations of the grains to each other. The metallic superconductor with the currently highest superconducting transition temperature, MgB2 with a Tc of 38.5 K, can be used in applications in polycrystalline form. One such application of interest are trapped field magnets or supermagnets, where the superconductor cooled in an applied magnetic field can trap the magnetic field as vortices at numerous flux pinning sites in the sample. When the external magnetic field is removed, the sample will stay magnetised as long as it is kept cool, and importantly, the trapped magnetic fields can be much higher as for any permanent magnet. However, the small size of the MgB2 grains in the 100–200 nanometre range requires a different approach when using the EBSD technique on such samples. The recently developed EBSD technique working in transmission mode (t‐EBSD) helps considerably to image such materials. In this approach, a tiny TEM slice has to be milled out from the original sample by using focused ion beam milling. To understand the properties of the flux pinning in the spark‐plasma sintered MgB2 sample, we had to identify the Kikuchi pattern of MgB4, which is another, non‐superconducting phase appearing at higher reaction temperatures required to compact the material. Using this information, we could perform EBSD scans using three different phases, MgB2, MgB4 and MgO. The EBSD mappings enable to see where the secondary phase particles are located in the sample, and to judge if the particles could work as flux pinning sites.

show abstract

Section: Introductionmentioning

confidence: 99%

Analysis of the microstructure of bulk MgB₂ using TEM, EBSD and t‐EBSD

Koblischka-Veneva

Koblischka

Schmauch

et al. 2019

Journal of Microscopy

View full text Add to dashboard Cite

show abstract

“…Transmission Kikuchi diffraction (TKD) in scanning electron microscope (SEM) is a recent technique derived from electron backscatter diffraction (EBSD) (Keller & Geiss, 2012;Sneddon et al, 2016). With the TKD technique, Kikuchi diffraction is produced in transmission with electron-transparent samples and patterns are typically recorded with a phosphor screen mounted on a charged-coupled device (CCD) or complementary metal-oxide-semiconductor camera (a promising emerging alternative is by direct detection (Wilkinson et al, 2013;Vespucci et al, 2015Vespucci et al, , 2017).…”

Section: Introductionmentioning

confidence: 99%

Depth Resolution Dependence on Sample Thickness and Incident Energy in On-Axis Transmission Kikuchi Diffraction in Scanning Electron Microscope (SEM)

Brodu

Bouzy

2017

Microsc Microanal

View full text Add to dashboard Cite

Transmission Kikuchi diffraction is an emerging technique aimed at producing orientation maps of the structure of materials with a nanometric lateral resolution. This study investigates experimentally the depth resolution of the on-axis configuration, via a twinned silicon bi-crystal sample specifically designed and fabricated. The measured depth resolution varies from 30 to 65 nm in the range 10-30 keV, with a close to linear dependence with incident energy and no dependence with the total sample thickness. The depth resolution is explained in terms of two mechanisms acting concomitantly: generation of Kikuchi diffraction all along the thickness of the sample, associated with continuous absorption on the way out. A model based on the electron mean free path is used to account for the dependence with incident energy of the depth resolution. In addition, based on the results in silicon, the use of the mean absorption coefficient is proposed to predict the depth resolution for any atomic number and incident energy.

show abstract

“…By comparison, in a TKD map only the particles that are distributed close to the bottom surface and have a size larger than the effective depth resolution can be detected. The existing surface-sensitive nature of TKD [14,31] thus needs to be taken into consideration, especially when analysing nano-crystalline materials with grain size of the order of the sample thickness. An example of a nanocrystalline sample of zirconium oxides scanned by TKD over the same region but from opposite directions is shown in Fig.…”

Section: Discussionmentioning

confidence: 99%

On the depth resolution of transmission Kikuchi diffraction (TKD) analysis

et al. 2019

View full text Add to dashboard Cite

In this paper, we have analysed the depth resolution that can be achieved by 'on-axis' transmission Kikuchi diffraction (TKD) using a Zr-Nb alloy. The results indicate that the signals contributing to detectable Kikuchi bands originate from a depth of approximately the mean free path of thermal diffuse scattering (λTDS) from the bottom surface of a thin foil sample. This existing surface sensitivity can thus lead to the observation of different grain structures when opposite sides of a nano-crystalline foil are facing the incident electron beam. These results also provide a guideline for the ideal sample thickness for TKD analysis of ≤ 6λTDS, or 21 times the elastic scattering mean free path (λMFP) for samples of high crystal symmetry. For samples of lower symmetry, a smaller thickness ≤ 3λTDS, or ≤ 10λMFP is suggested.

show abstract

Transmission Kikuchi diffraction in a scanning electron microscope: A review

Cited by 149 publications

References 95 publications

Analysis of the microstructure of bulk MgB₂ using TEM, EBSD and t‐EBSD

Analysis of the microstructure of bulk MgB₂ using TEM, EBSD and t‐EBSD

Depth Resolution Dependence on Sample Thickness and Incident Energy in On-Axis Transmission Kikuchi Diffraction in Scanning Electron Microscope (SEM)

On the depth resolution of transmission Kikuchi diffraction (TKD) analysis

Contact Info

Product

Resources

About

Transmission Kikuchi diffraction in a scanning electron microscope: A review

Cited by 149 publications

References 95 publications

Analysis of the microstructure of bulk MgB2 using TEM, EBSD and t‐EBSD

Analysis of the microstructure of bulk MgB2 using TEM, EBSD and t‐EBSD

Depth Resolution Dependence on Sample Thickness and Incident Energy in On-Axis Transmission Kikuchi Diffraction in Scanning Electron Microscope (SEM)

On the depth resolution of transmission Kikuchi diffraction (TKD) analysis

Contact Info

Product

Resources

About

Analysis of the microstructure of bulk MgB₂ using TEM, EBSD and t‐EBSD

Analysis of the microstructure of bulk MgB₂ using TEM, EBSD and t‐EBSD