I am trying to figure out the crystal plane that is forming during this etch of GaN, it is forming a 35deg angle or so. Any advice on going from an SEM image to figuring out the crystal plane, it is a bit more difficult with the added complexity of the hexagonal lattice here with GaN.
Thanks!
The problem is the "35deg angle or so" :-)
Ther are a few problems you have to deal with.
a) the image collected with your SEM. Can you trust it? (charging etc)
b) which projection direction I should use?
c) will two or more images help? (3D reconstruction of images)
d) which are the assumed growth planes?
e) there are many planes cover the same or very similar angles! Can you exclude any combined forms, i.e. (100) and (110) for hexagonal?
Compare the images with crystals in nature! a sloped plane does not automatically mean that this is a really grown plane (stairs!).
For GaN it should be clear which planes are possible. However, does it really make sense to assume slanted planes close to the root of the crystal?
To figure out crystal plane, better to avoid the SEM analysis. The data would not be reliable. It would be fine if you try to analyze the shape, size or homogeneity of a particular system. For crystal plane analysis try to analyze with TEM images.
Best Regard.
In your case, you must verify the growth direction. If you use (0001) sapphire, (111)Si etc, your GaN has growth direction of [0001], if then you can define the each planes by WZ crystal structure of GaN. If you use the special planed substrates such as r-plane sapphire, m-plane, for the non-polar or semi-polar GaN, you must measure the TEM for the determine the growth direction. Anyway, at first, you should define the growth direction of GaN NRs.
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