After seeing a reduction of pore size at 750 C, I decided to run three different soak times at a fixed acetylene concentration of 1 LPM. As expected, the longer soak time resulted in more occlusion.
It seems that the carbon growth is almost linear: 5 min treatment shrinks the pores by 5 nm and 10 min by 10 nm and 15 min by ~ 15 nm.
Here is a HRTEM image showing the boundary between the amorphous carbon ring and a Si nanocrystal:
750 C; 1 LPM C2H2; 10 min
Hopefully in the next week we will be submitting the following manuscript … X. Li, D. Johnson, W. Ma, H. Chung, J. Getpreecharsawas, J.L. McGrath, A.A. Shestopalov, Modification of Nanoporous Silicon Nitride with Stable and Functional Organic Monolayers, ACS Chemistry of Materials (2016) submitted. Here are the highlights … Traditional silanization of silicon materials uses…
In my last post I showed that using buffered solutions instead of Di-water we could obtained similar results with SC256 as we had with SC269. I used 20mM HEPES at pH7.5 with no salts and showed DDM diffusion through both “treated” and “untreated” SC256 samples. Additionally I showed that “treated” SC256 samples appeared to slow…
We have a high school student, Nikita, (from my Summer Nanotech class) who is volunteering in the lab. Jim and I have assigned him the project of exploring diffusion of very small molecules through porous and putatively nonporous membranes. Currently, we are focusing on hydrogen peroxide (H2O2 = 34Da) and detecting it with the Amplex…
Bernhard Group: Discoloration was observed during DNA separation experiments. Further study led to these results: No discoloration observed with low pH buffered NaCl. Discoloration with high pH buffered NaCl. Worried that Cl was the culprit, sodium acetate was tested. Discoloration observed with sodium acetate. In one early experiment, 4 areas were tested on one chip. …
Hello everyone! I plan to write several posts in the next couple of weeks about the laser annealing of our sputtered three-layer stack. This laser annealing experiment is done at Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory (ORNL). It is a collaborational proposal we submitted at the end of last year…
I continued to run some of the samples that I described in this post last week. These are P8 bEnd3 cells, seeded at 100000 cells/cm2 (just below confluence) and grown for 14 DAYS. The pnc-Si was SC126 that was RTP’ed. I measured the TEER of these samples for 2 weeks and then stained the cells…
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Wow, is the ordering that you are seeing on the inner wall of the HRTEM image of the pore, real? Since it does not appear in your other high-res images, it looks real to me. The spacing is just about right to be graphene, which would have a considerable number of implications, as our pore walls would start to resemble those of the CNT folks. We may also find interesting transport properties, if there is any truth in those theories.
You had mentioned something about “graphitization” at certain temperature regimes mentioned in some of the carbonization literature, I think. I wonder if there is a relation here? I’ll try to take another looks at those papers, but feel free to beat me to it…
It’s possible that graphene is growing… one paper observed graphitization at 800 C and we’re certainly close at 750 C. Interestingly, there’s no ordering when the carbon ring is < 5 nm but after a certain thickness epitaxial growth starts.
Makes sense to me. This is also a possible explanation for those odd chunks of carbon that you have been seeing protruding over pores before they are actually occluded. This is very odd because there are really no obvious PVD kinetics that would lead to features like that. However, graphene is a relatively stiff material and the interlayer adhesion is not strong. This would set up the potential for sloughing off of a few sheets here and there that could overhang the pores. If you happen to see such a feature overhanging a pore in Brian’s scope, it may be worth taking a closer look to see if you can actually make out a graphene lattice.
I wonder if this formation would be enhanced if you did a very high temp anneal following the deposition, after the acetylene is turned off. If some of the graphene has already started to seed, I wonder if the other carbon may also start to organize.