Editing Electron diffraction (section)

=== Reflection high-energy electron diffraction (RHEED) ===
{{main|RHEED}}{{anchor|Reflection high-energy electron diffraction}}
{{anchor|Figure 22}}{{anchor|Figure 23}}{{Multiple image
| total_width       = 250
| align             = left
| direction         = vertical
| image1            = Ewald sphere construction in Reflection high-energy electron diffraction (RHEED).svg
| caption1          = Figure 22: Ewald sphere in_RHEED, where higher-order Laue zones matter.
| image2            = Si111 7x7 ReconstructionB.png
| caption2          = Figure 23: RHEED pattern of a silicon (111) surface with a 7x7 reconstruction.
| alt1              = Connection between the electron wavevectors and reciprocal lattice vectors for reflection.
| alt2              = Experimental reflection electron diffraction pattern from a silicon surface
}}

Reflection high energy electron diffraction (RHEED),<ref name="Ichimiya">{{Cite book |last1=Ichimiya |first1=Ayahiko |url=https://www.worldcat.org/oclc/54529276 |title=Reflection high-energy electron diffraction |last2=Cohen |first2=Philip |date=2004 |publisher=Cambridge University Press |isbn=0-521-45373-9 |location=Cambridge, U.K. |pages=Chpt 4–19 |oclc=54529276}}</ref> is a [[analytical technique|technique]] used to characterize the surface of [[crystalline]] materials by reflecting electrons off a surface. As illustrated for the Ewald sphere construction in [[#Figure 22|Figure 22]], it uses mainly the higher-order Laue zones which have a reflection component. An experimental diffraction pattern is shown in [[#Figure 23|Figure 23]] and shows both rings from the higher-order Laue zones and streaky spots.<ref name="Peng" />{{Rp|location=Chpt 5}} RHEED systems gather information only from the surface layers of the sample, which distinguishes RHEED from other [[material characterization|materials characterization]] methods that also rely on diffraction of [[electrons]]. Transmission electron microscopy samples mainly the bulk of the sample, although in special cases it can provide surface information.<ref>{{Cite journal |last1=Kienzle |first1=Danielle M. |last2=Marks |first2=Laurence D. |date=2012 |title=Surface transmission electron diffraction for SrTiO3 surfaces |url=http://xlink.rsc.org/?DOI=c2ce25204j |journal=CrystEngComm |language=en |volume=14 |issue=23 |pages=7833 |doi=10.1039/c2ce25204j |bibcode=2012CEG....14.7833K |issn=1466-8033|url-access=subscription }}</ref> [[Low-energy electron diffraction]] (LEED) is also surface sensitive, and achieves surface sensitivity through the use of low energy electrons. The main uses of RHEED to date have been during thin film growth,<ref name=":16">{{Cite book |last=Braun |first=Wolfgang |url=https://www.worldcat.org/oclc/40857022 |title=Applied RHEED : reflection high-energy electron diffraction during crystal growth |date=1999 |publisher=Springer |isbn=3-540-65199-3 |location=Berlin |pages=Chpts 2–4, 7 |oclc=40857022}}</ref> as the geometry is amenable to simultaneous collection of the diffraction data and deposition. It can, for instance, be used to monitor surface roughness during growth by looking at both the shapes of the streaks in the diffraction pattern as well as variations in the intensities.<ref name="Ichimiya" /><ref name=":16" />