Graphene visibility vs. SiO2 thickness

Hi,

has anyone had any experience with visibility of single-layer flakes of graphene on substrates with non-optimum thickness of SiO2?
We've been shopping for some Silicon wafers with 300 nm of SiO2, but our supplier can only ensure the oxide thickness within 10% of the specified value. I was wondering if the substrates with, say, 320 nm of SiO2 would still allow the flakes to be visible with an optical microscope.

The only paper I found specifically addressing this problem ("Making graphene visible", http://arxiv.org/abs/0705.0259 ) has a calculated visibility plot which would suggest that at oxide thickness of 320 nm the contrast would reduce and shift to a different wavelength (compared to the thickness of 300 nm) and I was wondering how much of an issue this would be in practice.
 

TeethWhitener

Science Advisor
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It won’t matter so much. Graphene is pretty easy to see on 250-300nm surfaces (it’s even easier to see on 100 non surfaces).
 

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