I've been working on CVD growth graphene for two years. I growth graphene on copper substrate. I didn't have any problem about producing graphene until nowadays but I've some problem about growth graphene since two weeks. Yes, I produce graphene but it's not look like previous ones. In before experiments, I grew homogenous graphene but now, our graphene is not homogenous. Sometimes, I can't see graphene peak on some of part when I am checking it with Raman. I've checked flowmeter and also pump system but there is no any different from previous ones. But I've also reliazed that our quartz tube which is used graphene growth is getting dirty. Could this dirties on quartz tube effect on quality of graphene?
From my experience a dirty quartz tube affects the growth of CVD graphene. During the high temperature growth, Cu foil also evaporates which then deposits on the quartz tube. Also, any gas leakage in the system will also affect the growth. Nevertheless, the quartz tube or the CVD graphene growth condition must be as contamination free as possible. Try to clean the tube after several experiments. Or use two tubes by replacing the tube used for the experiment with a clean one. In the mean time clean the used one.
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Hi,
Probably, it might be due to the deposition.contamination of amorphous carbon inside of tube. Once time in my experiment also I had shown similar kind of problem. Try to do proper cleaning of accessories by ethanol/acetone and purging by N2.
First of all, thank you very much for your suggestions.. I tried to clean the tube under high temperature using O2 and then I did another experiment using same conditions but unfortunatelly the results are'nt same as previous ones. I've an another problem also.. After each experiment, I reliazed that some amorphous carbon ioccured inside the tube around. Our growth temperature at 1000oC, I'm thinking that, if the machine temparature higher than 1000oC, the methane decomposition rate is getting higher and this results effect our graphene quality. could it be possible??
1. At around 1000C, the dehydrodimerization of methane on amorphous carbon (dirt) deposited on quartz produces some ethylene, which is a better nucleation agent for graphene on copper. Therefore, the quartz tube should be cleaned of dirt as much as possible.
2. Try to add some minuscule amount of oxygen gas or water wapor into the gas reactants. These will suppress the nucleation of graphene by forming copper oxide covered surface, and graphene leaflets of larger size and more homogeneous will be produced. If so happens, it would mean that in previous runs you've got rid of oxygen in the system more successfully.
Good luck.
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