I have read some article of SiC thin films. They used adventitious carbon for charge correction. My question is, since SiC already contain carbon, so how can we used carbon as charge correction?
X-ray Photoelectron spectroscopy
Analyzes the spectrum of C1s, The spectrum must have at least 2 components,
If Si-C is present this must be the most intense peak, other smaller peak to the right corresponds to the adventitious C, this smaller peak you have to correct it to 284.8 eV, so the most intense peak should be in approx. 283 eV. Apply that charge correction to all spectra that were measured.
best regards
Analyzes the spectrum of C1s, The spectrum must have at least 2 components,
If Si-C is present this must be the most intense peak, other smaller peak to the right corresponds to the adventitious C, this smaller peak you have to correct it to 284.8 eV, so the most intense peak should be in approx. 283 eV. Apply that charge correction to all spectra that were measured.
best regards
Thank you J. A. Torres for your opinion.
In my opinion, if our sample have carbon in it, it is not fair to use carbon for charge correction. It is more suitable to use pure element like gold as charge reference.
I have go through some article that has carbon in their sample and they also used adventitious carbon as charge reference. I'm just wondering under what condition they used carbon as charge reference.
It will be slightly more challenging but if you you are aware about all the details of the more convoluted C 1s spectrum and can resolve it, there is no reason not to try. Charging on gold surfaces is different so I am not sure if there is any way to use it.
I would not recommend to use adventitious C on Si-C, because if you have relatively small amount of carbon comntaminations then the peak that supposed to be at 284.8 eV will be very weak and relatively broad. Also when you are trying to adjust the parameters for charge neutralization you normally uses pass energy of 40 eV and relatively high scanning speed (bigger step), otherwise it will take ages for adjustment. So in this case it will quite difficult to track the quality of the neutralization. From my point of view, it might be better to adjust the BE scale according to the C1s Si-C peak and then check the spectrum of Si2p. Silicon carbide has very typical BE value, so you will be able to check if your adjustment was correct or not. Also if you can see some oxygen, then you should check O1s peak as well. If you have very thin (
Other references can be used such as one of the Si 2p components. See, please, the reference:
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms,
Volume 365, Part A, 15 December 2015, Pages 39-43.
The gold has many problems as a reference. See, for instance, point 7.2.2 in: Designation: E 1523 – 03. Standard Guide to Charge Control and Charge Referencing Techniques in X-Ray Photoelectron Spectroscopy.
I would not recommend using C 1s of adventitious carbon as a BE reference.
We have found out recently that the position of the C 1s of adventitious carbon varies by as much as 1.4 eV depending on the sample. This was for a series of transition metal nitride thin films all with good conductivity so charging was not an issue.
We found out that BE of C 1s peak correlates with the sample work function in such way that the sum of both is constant. For high work function samples you will find C 1s C-C peak at significantly lower BE than for low work function samples. It can be anything between 284.0 and 285.5 eV.
I do not see any reason why this should not be the case also for SiC. I suspect that the position of C 1s peak of adventitious carbon will change depending on the work function of your sample.
Our paper is attached for your reference.
https://www.researchgate.net/project/think-twice-before-you-use-C-1s-as-a-binding-energy-reference-in-your-XPS-work
Dear Anton, Ana and G. Greczynski, I would like to say thank you very much for your thoughts regarding this question.
The problem with using adventitious carbon as a reference in XPS pointed by Dr. G. Greczynski, is common to all the external references (gold coating, for instance). That's why it is preferable to use an internal reference.
If your sample has a lot of carbon contamination you can use the difference between carbon 1s and Si2p3/2 to identify the SiC position. For a clean (perfect LEED) SiC-6H:H (0001) surface we obtain 181.8eV
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