I'm currently working on graphene growth by using LPCVD with a hydrocarbon source from mixture of methane and hydrogen. For a while, it seemed to be working without any problems; however, I'm stuck and have no idea why I am facing problems.
I used copper foil 25um from alfa aesar. This copper foil is not 100% pure copper. Thus, after annealing it at high temperature (~1000) I always get unwanted particles consisting of silicon, aluminum etc.
To avoid this, I employed electropolishing which seemed to be working fine for a while.
I am now getting impurities again with aluminum, silicon etc. They have somewhat specific arrays, and I have no idea why this is happening.
I didn't change a single condition, but the particles with similar shapes still occur on my graphene.
Can anyone give some help or explanation?
The attached image is a SEM image of graphene.
A wire shaped image indicates the backside of graphene, so please disregard the backside graphene.
Seems that during annealing and polishing impurities migrate to the cooper grain boundaries. And CVD process stimulate impurities to migrate on graphene. On the picture we can see the clusters of impurities. Maybe you need to remove all graphene and particles and use this foil for CVD again?
Annealing is a heat process whereby a metal is heated to a specific temperature /colour and then allowed to cool slowly. Alfa aesar quality of copper foil contains an infinisimally small amount of Al ( exact amount –a trade secret) while even the best quality of copper sample contaions 0.2 to5.0 ppm of Si along with traces of Cu2O.In a way, the Alfa aesar copper foil may be considered to be analogous to an alloy consiting of Cu,Cu2O,Si,Al; all get separated during annealing to give tests for Si and Al
Dear Jason, did you find any solution for these impurities? Because, I am having a similar impurity problem, containing Si and O, for a while.
I also have exactly same problem, i doubt on quality of that Alfa aser copper (46365 and 13382). can you mention what is your product number..
https://www.researchgate.net/post/Has_anyone_any_advice_on_how_to_synthesize_high_quality_of_graphene?_tpcectx=qa_overview_following
I have same problem, I found Si and O impurities when copper foil annealed at 1000C in H2 environment. Do you have any idea how to solve this problem? The copper foil is from MTI corporation and it has 25um thickness.
I believe our recent paper can also be helpful for people still looking for an explanation to similar problems.
Article The Effects of Acid Pretreatment and Surface Stresses on the...
I hope our paper below also helps to minimize impurities on graphene grown over copper foils.
Article Relationship between heating atmosphere and copper foil impu...
This work tracing the white impurities on CVD graphene.
Article Improved control in elimination of white impurities on graph...
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering
- Annealing