Parameter: 0.3 sccm CH4 + 2 sccm H2 / 1000 C / 350 mTorr / 1-15 min
Pretreatment: Electropolishing + 30 min anneal with 10 sccm H2
Tried several times but get no carbon on copper, then tried to clean the quartz tube and the sample holder and check the impermeability. There is a small leakage but fixed now. Then tried three times with growth time 1, 3 and 15 min respectively but still cannot get any graphene. The Raman spectrum just shows the same signal as the bare copper but when the samples were heated at 160 C for several minutes, they didn’t get oxidized, which is different from the bare copper.
Has anyone met with such issue or know the reason?
Have you ever used that particular Raman spectrometer for single-layer graphene? We once had the problem that we didn't see any graphene on the substrate with the regular Raman spectrometer, but when we put it in a confocal Raman microscope, we suddenly had plenty of G mode signal.
Jürgen Weippert I’m not familiar with Raman. I guess I just used a regular one but I have found the peak of silicon and graphene on the silicon wafer. So I don’t know whether it’s the reason why I can’t see graphene on copper foil.
Usually, for the oxidation, you need way higher temperatures. For example, in my case for porous materials, I use a few hundreds celsius.
Anyways, make sure you do not have any leakages in your CVD set-up.
Also, double-check if the temperature on the graphene foil is not too high.
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