Hi,
what is different between specular reflection and diffraction in reflection
high-energy electron diffraction(RHEED)?
and how to decide the specular reflection spot position along the 00 rod
wnen the RHEED patterns are thin streaks?

Thanks a lot.

Hi,

This may be helpful: Reflection High Energy Electron Diffraction (RHEED)

This is from complete book Fabrication and Characterization of Photonic Band Gap Materials

Hope this helps.

Hi Daliss,

It's six years since I did RHEED ... anyway:

The position of the specular reflection is just geometry - if you know
the angle of incidence of the beam then you also know where the specular
spot must be. It's usually the brightest spot in the diffraction image
if you're "far off" any main axis of symmetry, but close to a main rod
interferences with the diffraction pattern may reduce the intensity of
the specular spot so much that it's no longer clearly discernible. Yes,
it is possible for the specular reflection to disappear (for flat
surfaces; it'll always disappear for a very bumpy one as you'll then
see volume diffraction patterns - but since you say you get streaks
that's not an issue for you).

If your sample can be rotated azimutally, twist it out of the 00
direction until you see one spot on the central streak brighten
significantly. The specular reflection won't move when you rotate
the sample, since geometry says the rocking angle stays the same and
therefore the direction of reflection as well. Spots from diffraction
will move.

Once you've found it, simply mark the position and go back to the 00
direction.

If you're doing rocking curves (i.e. vary the polar angle of incidence),
you have to measure start/end reference positions for the spec spot for
the range of incidence that you want to use, mark these positions, go
to the start angle of incidence, the 00 direction and the start position
for the spec spot, and then interpolate the spec spot position as you
increase the angle of incidence. If your magnets aren't linear enough
you may have to create a whole series of reference positions, though.

Bye,
Frank Hofmann