We have two different sputtering targets for Si3N4 deposition in the magnetron sputtering lab. One is white and other is greyish black. Both are tagged as 99.99% purity. Can anyone please explain the difference among these two targets?
i know from grey Si3N4 when I order some industry ceramic. kind of bulk SiN (large grain)
I believe the microstructure of the target is different. But it can only be a surface state difference.
the white one may be formed from transparent/semi-transparent small grains, which totally look white.
check the roughness state?
the best is to make some analysis of the surface (Oxygen contamination)
and glacing angle XRD for the grain size on the surface..
just a guess!
May be one was overheated under high supplied power and the structure was changed.
Just found on some website:
Stoichiometric Silicon Nitride (Si3N4) is a white, This material is slightly silicon rich, making it grey, or translucent black, in color
http://www.plasmaterials.com/september-blog.php
I am still not sure Sir, I cant characterize through XRD due to very large size of target 3" diameter. I can`t use the white one (It is broken). So I am using the black one.
As Claus Moseke just said, the grey one is a used target. When you buy those targets new, they are probably white in color. After sputtering a while, the stoichiometry of your target changes slightly, due to different sputter yields of Si and N. Thus the color of your target changes from white to grey. This is no problem, you can still use the grey one.
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