Dear
I'm trying to define graphene channel by using GXR/LOR photoresists
In my case, I transfer graphene on top of ALD Al2O3 through wet transfer method
But, when finished the etching step (low power O2 plasma short time) for graphene region define, I found that no graphene exist.
I eliminate GXR/LOR using remover PG 6 hours + IPA rinse
Could you tell me how to enhance adhesion between graphene and Al2O3? (currently I trying to use O2 plasma to enhance the wettability of Al2O3, but still not did)
Dear Shinho Kim , let me see if I´m getting your process correctly:
1- You have a substrate where you deposited ALD Al2O3, then
2- Wet transfer of graphene on top of ALD Al2O3
3- Coating of graphene with GXR/LOR photoresist
4- Phothomask and G-line exposure to define the channel you want.
5- Developing the resist and rinsing.
6- Plasma etching (O2, low power, short time) to define graphene region.
7- Removing resit (PG 6h +IPA rinse)
The question is: Where the graphene is lost?? Probably in the last step, (7) because you think it is poorly anchored to the Al2O3 and it is removed with the resist.
Pristine graphene is hydrophobic, and Al2O3 is relatively hydrophilic, so they are poorly adhered each other. A way to improve adhesion consists on making the surface of Al2O3 hydrophobic by surface functionalization with -CH3 groups. In the following article the authors show clearly how you can choose the Al2O3 surface wettability:
Article Bottom-gate coplanar graphene transistors with enhanced grap...
Alternatively, you could modify graphen surface to make it more hydrophilic to match the surface properties of Al2O3, minimising detaching. But may be in this way you would be modifying the transport properties of the graphene layer. Some authors manage this problem using double layer graphene, just modifying one layer to improve adhesion while the untouched layer keeps the graphene properties.
Hope it helps.
@Manuel Gómez
Thanks very much for your reply
The process is exactly what you mentioned
The most recent result shows that even I didn't any treatment on the surface of Al2O3, I successfully patterned the graphene area (there is a residue problem. but, I can confirm apparent graphene Raman spectrum).
I don't know why but it seems like there will be a mistake for graphene handling
In the case of surface modification, I cannot try the same method as mentioned in the paper (still I don't have the facility for that). But surface modification will be a good option for stable device fabrication condition
I will try the other surface modification methods.
Thanks
Hi Shinho Kim , I didn´t mentioned it before, but while I was looking for some information, most papers dealing with ALD Al2O3 and graphene proceed in the reverse way you do, I mean, they deposited Al2O3 on top of graphene. May be this method could be adapted for fabricating your graphene channel... However, surface modification looks like necessary to avoid detaching.
Good luck!
Manuel
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