Electron backscatter diffraction: Difference between revisions

Revision as of 16:04, 1 May 2024

Revision as of 01:25, 11 May 2024

Line 28:

=== Sample preparation ===

[[File:EBSP degradation.tif|thumb|Pattern degradation due to carbon deposition in a highly magnified ___location after 3-hour EBSPs acquisition around a deformation twin in the ferrite phase of [[duplex stainless steel]]<ref name=":31" />|alt=Electron backscatter diffraction's pattern degradation due to carbon deposition in a highly magnified ___location after 3-hour EBSPs acquisition around a deformation twin in the ferrite phase of duplex stainless steel.]]

The sample should be [[Outgassing|vacuum stable.]] It is typically mounted using a conductive compound (e.g. an [[Thermosetting polymer|epoxy thermoset]] filled with Cu), which minimises image drift and sample charging under electron beam irradiation. EBSP quality is sensitive to surface preparation. Typically the sample is ground using [[Sandpaper|SiC papers]] from 240 down to 4000 grit, and polished using diamond paste (from 9 to 1&nbsp;µmμm) then in 50&nbsp;nm [[colloidal silica]]. Afterwards, it is cleaned in [[ethanol]], rinsed with [[deionised water]], and dried with a hot air blower. This may be followed by [[Ion milling machine|ion beam polishing]], for final surface preparation.<ref>{{Cite journal |last1=Nowell |first1=Matthew M |last2=Witt |first2=Ronald A |last3=True |first3=Brian W |date=2005 |title=EBSD Sample Preparation: Techniques, Tips, and Tricks |journal=Microscopy Today |volume=13 |issue=4 |pages=44–49 |doi=10.1017/s1551929500053669 |s2cid=139585885 |doi-access=free }}</ref><ref name=":32">{{Cite journal |last1=Koko |first1=Abdalrhaman |last2=Elmukashfi |first2=Elsiddig |last3=Becker |first3=Thorsten H. |last4=Karamched |first4=Phani S. |last5=Wilkinson |first5=Angus J. |last6=Marrow |first6=T. James |date=2022 |title=In situ characterisation of the strain fields of intragranular slip bands in ferrite by high-resolution electron backscatter diffraction|journal=Acta Materialia |volume=239 |pages=118284 |doi=10.1016/j.actamat.2022.118284 |bibcode=2022AcMat.23918284K |s2cid=251783802 |doi-access=free }}{{Creative Commons text attribution notice|cc=by4|from this source=yes}}</ref><ref>{{Cite web |date=2013-11-15 |title=Sample Preparation Techniques for EBSD Analysis (Electron Backscatter Diffraction) |url=https://www.azonano.com/article.aspx?ArticleID=3702 |website=AZoNano.com |archive-date=2023-03-02 |archive-url=https://web.archive.org/web/20230302142456/https://www.azonano.com/article.aspx?ArticleID=3702 |url-status=live }}</ref>

Inside the SEM, the size of the measurement area determines local resolution and measurement time.<ref>{{Cite book |last=Williams |first=B. David |title=Transmission electron microscopy: a textbook for materials science. |date=2009 |publisher=Plenum Press |isbn=978-0-387-76501-3 |pages=11 |oclc=633626308}}</ref> Usual settings for high-quality EBSPs are 15 nA current, 20 kV beam energy, 18 mm working distance, long exposure time, and minimal CCD pixel binning.<ref>{{Cite journal |last1=Britton |first1=T.B. |last2=Jiang |first2=J. |last3=Clough |first3=R. |last4=Tarleton |first4=E. |last5=Kirkland |first5=A.I. |last6=Wilkinson |first6=A.J. |date=2013 |title=Assessing the precision of strain measurements using electron backscatter diffraction – Part 2: Experimental demonstration |journal=Ultramicroscopy |volume=135 |pages=136–141 |doi=10.1016/j.ultramic.2013.08.006 |pmid=24034981 }}</ref><ref>{{Cite journal |last1=Jiang |first1=J. |last2=Britton |first2=T.B. |last3=Wilkinson |first3=A.J. |date=2013 |title=Evolution of dislocation density distributions in copper during tensile deformation |journal=Acta Materialia |volume=61 |issue=19 |pages=7227–7239 |doi=10.1016/j.actamat.2013.08.027 |bibcode=2013AcMat..61.7227J|doi-access=free }}</ref><ref>{{Cite journal |last1=Abdolvand |first1=Hamidreza |last2=Wilkinson |first2=Angus J. |date=2016|title=On the effects of reorientation and shear transfer during twin formation: Comparison between high-resolution electron backscatter diffraction experiments and a crystal plasticity finite element model |journal=International Journal of Plasticity |volume=84 |pages=160–182 |doi=10.1016/j.ijplas.2016.05.006 |s2cid=139049848|doi-access=free }}</ref><ref name=":29">{{Cite journal |last1=Koko |first1=Abdalrhaman |last2=Becker |first2=Thorsten H. |last3=Elmukashfi |first3=Elsiddig |last4=Pugno |first4=Nicola M. |last5=Wilkinson |first5=Angus J. |last6=Marrow |first6=T. James |date=2023 |title=HR-EBSD analysis of in situ stable crack growth at the micron scale |journal=Journal of the Mechanics and Physics of Solids |volume=172 |pages=105173 |arxiv=2206.10243 |bibcode=2023JMPSo.17205173K |doi=10.1016/j.jmps.2022.105173 |s2cid=249889649 }}</ref> The EBSD phosphor screen is set at an 18&nbsp;mm working distance and a map's step size of less than 0.5&nbsp;µmμm for [[Infinitesimal strain theory|strain]] and [[Geometrically necessary dislocations|dislocations density]] analysis.<ref name=":30" /><ref name=":31" />

Decomposition of gaseous hydrocarbons and also hydrocarbons on the surface of samples by the electron beam inside the microscope results in carbon deposition,<ref>{{Cite journal |last1=Griffiths |first1=A J V |last2=Walther |first2=T |date=2010 |title=Quantification of carbon contamination under electron beam irradiation in a scanning transmission electron microscope and its suppression by plasma cleaning |journal=Journal of Physics: Conference Series |volume=241 |issue=1 |pages=012017 |bibcode=2010JPhCS.241a2017G |doi=10.1088/1742-6596/241/1/012017 |s2cid=250689401|doi-access=free }}</ref> which degrades the quality of EBSPs inside the probed area compared to the EBSPs outside the acquisition window. The gradient of pattern degradation increases moving inside the probed zone with an apparent accumulation of deposited carbon. The black spots from the beam instant-induced carbon deposition also highlight the immediate deposition even if agglomeration did not happen.<ref name=":4">{{Cite journal |last1=Koko |first1=Abdalrhaman |last2=Elmukashfi |first2=Elsiddig |last3=Dragnevski |first3=Kalin |last4=Wilkinson |first4=Angus J. |last5=Marrow |first5=Thomas James |date=2021 |title=J-integral analysis of the elastic strain fields of ferrite deformation twins using electron backscatter diffraction |journal=Acta Materialia |volume=218 |pages=117203 |bibcode=2021AcMat.21817203K |doi=10.1016/j.actamat.2021.117203 |url=https://ora.ox.ac.uk/objects/uuid:4071edea-3bfc-4d2b-8d32-c3b05bd73372 |access-date=20 March 2023 |archive-date=5 July 2022 |archive-url=https://web.archive.org/web/20220705095819/https://ora.ox.ac.uk/objects/uuid:4071edea-3bfc-4d2b-8d32-c3b05bd73372 |url-status=live }}</ref><ref name=":12">{{Cite journal |last1=Bachmann |first1=F. |last2=Hielscher |first2=Ralf |last3=Schaeben |first3=Helmut |date=2010 |title=Texture Analysis with MTEX – Free and Open Source Software Toolbox |journal=Solid State Phenomena |volume=160 |pages=63–68 |doi=10.4028/www.scientific.net/SSP.160.63 |s2cid=136017346}}</ref>

Line 37:

{{Further information|Electron scattering}}

[[File:Electron Interaction with Matter.svg|thumb|Electron-matter interaction volume and various types of signal generated|alt=Pictorial diagram showing signals generated when an electron beam interacts with a sample of matter. At the top, the primary electron beam impinges on the sample. Various types of emissions are shown in order of increasing penetration depth of the beam. Near the top are Auger Electrons, followed by Secondary Electrons, then Backscattered Electrons, all emerging in the general direction towards the impinging beam. Next are four types of radiation (shown with wavy arrows): Characteristic X-rays, Continuum X-rays, Cathodo-luminescence, and Fluorescent X-rays. The later two are shown as being emitted from the same depth. Finally, shown having passed through the body of the sample are, in increasing order of angular displacement from the beam axis, Transmitted Electrons, Diffracted Electrons, and Scattered Elections.]]

There is no agreement about the definition of depth resolution. For example, it can be defined as the depth where ~92% of the signal is generated,<ref>{{Cite journal |last1=Powell |first1=C. J. |last2=Jablonski |first2=A. |date=2011 |title=Surface Sensitivity of Auger-Electron Spectroscopy and X-ray Photoelectron Spectroscopy |journal=Journal of Surface Analysis |volume=17 |issue=3 |pages=170–176 |doi=10.1384/jsa.17.170|doi-access=free }}</ref><ref>{{Cite journal |last1=Piňos |first1=J. |last2=Mikmeková |first2=Š. |last3=Frank |first3=L. |date=2017 |title=About the information depth of backscattered electron imaging |journal=Journal of Microscopy |volume=266 |issue=3 |pages=335–342 |doi=10.1111/jmi.12542|pmid=28248420 |s2cid=35266526 }}</ref> or defined by pattern quality,<ref name=":27" /> or can be as ambiguous as "where useful information is obtained".<ref>{{Cite journal |last=Seah |first=M. P. |date=2001 |title=Summary of ISO/TC 201 Standard: VIII, ISO 18115:2001—Surface chemical analysis—Vocabulary|journal=Surface and Interface Analysis |volume=31 |issue=11 |pages=1048–1049 |doi=10.1002/sia.1139 |s2cid=97982609 }}</ref> Even for a given definition, depth resolution increases with electron energy and decreases with the average atomic mass of the elements making up the studied material: for example, it was estimated as 40 nm for Si and 10 nm for Ni at 20 kV energy.<ref>{{Cite journal |last=Dingley |first=D. |date=2004 |title=Progressive steps in the development of electron backscatter diffraction and orientation imaging microscopy: EBSD AND OIM |journal=Journal of Microscopy |volume=213 |issue=3 |pages=214–224 |doi=10.1111/j.0022-2720.2004.01321.x |pmid=15009688 |s2cid=41385346 }}</ref> Unusually small values were reported for materials whose structure and composition vary along the thickness. For example, coating monocrystalline silicon with a few nm of amorphous chromium reduces the depth resolution to a few nm at 15 kV energy.<ref name=":27">{{Cite journal |last=Zaefferer |first=S. |date=2007|title=On the formation mechanisms, spatial resolution and intensity of backscatter Kikuchi patterns |journal=Ultramicroscopy |volume=107 |issue=2 |pages=254–266 |doi=10.1016/j.ultramic.2006.08.007 |pmid=17055170 }}</ref> In contrast, Isabell and David<ref name=":28">{{Cite journal |last1=Isabell |first1=Thomas C. |last2=Dravid |first2=Vinayak P. |date=1997-06-01 |title=Resolution and sensitivity of electron backscattered diffraction in a cold field emission gun SEM |journal=Ultramicroscopy |series=Frontiers in Electron Microscopy in Materials Science |volume=67 |issue=1 |pages=59–68 |doi=10.1016/S0304-3991(97)00003-X }}</ref> concluded that depth resolution in homogeneous crystals could also extend up to 1&nbsp;µmμm due to [[inelastic scattering]] (including tangential smearing and channelling effect).<ref name=":32" />

A recent comparison between reports on EBSD depth resolution, Koko et al<ref name=":32" /> indicated that most publications do not present a rationale for the definition of depth resolution, while not including information on the beam size, tilt angle, beam-to-sample and sample-to-detector distances.<ref name=":32" /> These are critical parameters for determining or simulating the depth resolution.<ref name=":28" /> The beam current is generally not considered to affect the depth resolution in experiments or simulations. However, it affects the beam spot size and [[signal-to-noise ratio]], and hence, indirectly, the details of the pattern and its depth information.<ref>{{Cite journal |last=Humphreys |first=F. J |date=2004 |title=Characterisation of fine-scale microstructures by electron backscatter diffraction (EBSD) |journal=Scripta Materialia |series=Viewpoint set no. 35. Metals and alloys with a structural scale from the micrometer to the atomic dimensions |volume=51 |issue=8 |pages=771–776 |doi=10.1016/j.scriptamat.2004.05.016}}</ref><ref>{{Citation |last1=Goldstein |first1=Joseph I. |title=The Visibility of Features in SEM Images |date=2018 |work=Scanning Electron Microscopy and X-Ray Microanalysis |pages=123–131 |editor-last=Goldstein |editor-first=Joseph I. |place=New York, New York |publisher=Springer |doi=10.1007/978-1-4939-6676-9_8 |isbn=978-1-4939-6676-9 |last2=Newbury |first2=Dale E. |last3=Michael |first3=Joseph R. |last4=Ritchie |first4=Nicholas W. M. |last5=Scott |first5=John Henry J. |last6=Joy |first6=David C. |editor2-last=Newbury |editor2-first=Dale E. |editor3-last=Michael |editor3-first=Joseph R. |editor4-last=Ritchie |editor4-first=Nicholas W.M. |doi-access=free }}</ref><ref name=":24" />

Line 130:

|0.006° (1×10⁻⁴ rad)

|-

!GND @ 1&nbsp;µmμm step

In lines/m² (b = 0.3&nbsp;nm)