Methane and hydrogen are used to synthesize large single-crystal graphene. Flow rates of are 0.01sccm and 40sccm respectively. The Cu foil is electropolished to flatten the surface before growth.
Thanks for your answer. The holes may be caused by unclean surface. But I cannot understand how the cracks appear.
when we taking grown cu foil after growth there is a chance of bending Cu foil. Is this stretching can be able to break the graphene sample? (I am not sure)
Thanks for the interesting SEM image.
- The cracks in the image seem to be related with circular dots. Do you know the origin of the dots?
- The cracks are nearly parallel with one another. Is there any correlation between the crystal orientation of Cu and the crack direction? You may need EBSD analysis.
- Do you have any AFM (atomic force microscopy) image around the crack? If you send the sample to me, I'd like to scan the cracks using AFM. (We have some experience on the crack analysis on graphene. See the article below.)
Article Double-layer CVD graphene as stretchable transparent electrodes
It all about your catalyst surface, In this case cu surface is not clean and pre anneal before growth it might help.
Maybe I didn't describe it well. Before graphene growth, the graphene had been pre-annealed for 1 hour in H2 atmosphere. I doubt the cracks may be caused by bending.
Maybe check the paper recently published in Nanoscale:
Role of the Cu substrate in the growth of ultra-flat crack-free highly-crystalline single-layer graphene
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