I am fabricating a CNT FET device.
I read that applying drops of CNT suspense in DMF will allow me to deposit the CNT in place before I add the electrodes with a photolithography step and metal deposition.
my questions are:
1. How can I make sure the CNT's are in place? (will refractive microscope work in dark field mode?)
2. Will it also work with ethanol instead of DMF?
3. What concentration (mg/ml) of the suspense should I use?
Thank you!
Dear Or,
CNTs can be dispersed into DI water with the assistance of surfactant such as SDS to make a solution. The details you can find from the below publication.
https://doi.org/10.1002/adfm.200902369
Hope it helps
Best wishes
Xuhua
Hello Or Zolti ,
Do you know which CNTs you are using and their properties?
We use DMF and NMP for most of our CNT dispersions. We typically use densities of 1-10 mg.mL-1, depending on the application. We use ultrasonic agitation for 5-30 min to improve the quality of the dispersion.
You can use water to create disperions, but the densities that you can use to create good dispersions will be much lower, in the order of 1 mg.L-1.
You can use ethanol but we have found DMF and NMP to provide more reliable dispersions.
In regards to how you can verify that the CNTs are in place - it will very much depend on the area of your device you add the dispersion, the density of your dispersion and the volume of dispersion you add to said area.
Jules
Xuhua Wang thank you I read the article.
Jules Lloyd Hammond I am using SWCNT with O.D. of 1-3nm and length of ~5um. The disspersion area is 6um X 100um. I saw in other studies they used SEM, do you know of table side test (before I fabricate the next lithography stage so that I will be able to know if there are CNTs in the required area) like light microscopy (DF or filter based)?
Thank you,
Or
NMP is a good solvent among the options, and sonication is a great way to disperse the nanotubes into it.
SEM is likely the best way to ensure the presence of CNTs. If you are worried about carbon deposition, then AFM is also good. At times a light microscope can show a slight contrast difference between areas that have CNTs and areas that have none, but it can be quite subtle and depends greatly on the substrate (i.e. the SiO2 thickness in your case, assuming your SiO2 is a thin film on a Si substrate).
If you are looking for something extremely rudimentary, you may even be able to simply use a multimeter to test resistance between two points you expect to be in the CNT covered area. You will have to be gentle with the probes. Pogo pins or micromanipulators may be a better contact mechanism for this test if you have them. I have used each of these options successfully.
Ethanol may work but DMF is likely better.
Somewhere around 3 mg/mL should be a good starting point.
- Steven
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