Getting closer to more etching

Yesterday my contact at OU and I were able to perform a few different soaking tests in solvents in order to determine if they had any effect on the sample cleanliness.  First, we characterized the surface using a Dynamic Interference Contract microscope and chose an area that could be found again.  The DIC microscope is different in that it allows one to see various layers on a sample.  So we were able to see that aside from multilayers of spheres there seemed to be another layer of stuff on the monolayers of spheres, which we believe to be left over surfactant from the solution used to layer the spheres.  Then we let the samples soak in different solvents and air dry.  Then we looked at the samples again under the microscope, looking for differences in bead number and whether or not we could see and "scum" on the surface of the beads.  We saw that some of the solvents completely removed the spheres while others did very little.  We saw that one sample had less of a scum layer than before, almost non at all by what we could see, but did removed most of the beads.  However, this sample has enough on it to try etching with and see if our results improve from last time.  My contact will be away next week but once he returns we may be able to do another series of etching!!  On the other side of the project, the group at TU still has not been able to get the e-beam and the controlling computer to "talk" to each other yet.  Therefore I will not be making a trip there this week, and instead will be trying to improve the cleanliness of the samples and the PMMA layer to etched once the e-beam is up and running.

Getting the Software Down

Last Thursday on my trip to Tulsa I was able to begin designing a template to be used with the e-beam hardware.  Unfortunately the e-beam and the SEM are not yet "talking" to each other, but the software itself is still operational.  Therefore, I was able to read the manual and make some decisions that will make using the e-beam much easier, as soon as it is operational.  One concern that the professor I've been working with at TU is that because the e-beam is different than the one they used previously (with the group before me) is that the counts/dose ( the energy delivered to the sample per specified area, line or spot) will be different.  This means that we can't just use the settings that were used prior and expect the same results right off the bat.
In order to determine the correct dose, I made a template the features several lines which I made different colors on the program.  Then I can make each differently colored line a different dosage and examine the results to determine which lines didn't go deep enough, which ones gave poor resolution and which give the best results.  There are still other optimization problems that go along with the system, such as the SEM optimization itself (stigmators, apertures, etc.) but I have quite a bit of practice with this and there is a very skilled technician available to assist if needed.
If the e-beam and software are not communicating by Thursday this week then I will forego a trip there this week as I feel that there is not much I can really do until that is completed, at least not that would warrant my driving there.
On the other side of the project (terraces) I am also moving forward.  I have made 5 200 nm sphere samples and today or tomorrow I am working with a research scientist here at OU to determine if there is anyway to clean the surfactant of the surface of the sphere layers using different solvents.  We will immerse the samples in 4 different solvents and keep one a control in order to determine what effect they have on their cleaning capabilities.  The reason for this detour is that using the etching system will be better optimized is the samples are as free of impurities (surfactant and other junk besides the spheres) as possible because it will create inconsistencies in the etching depth and performance.  Once we have determined that we have obtained as clean a sample as possible we are going to etch again at a length of time longer than 30 seconds but shorter than 5 min.  This should yield pillars and hopefully those pillars have a fine enough relief (edge on the top) that we can start using AFM to view surfactants on them!
I'll admit that we are moving slower than I had hoped, but at this point moving slowly is better than not moving at all! 

Tulsa Trenches and OU Terraces

Yesterday in Tulsa went very well.  Despite the e-beam technician being on vacation until next week I have still been able to make some good strides in sample preparation.  The AFM tech at TU had some trouble getting a good PMMA layer depth reading on the samples from last week. He said they were in the neighborhood of 50 nm, which is about a third of what we were expecting based on the notes of the students previously working on this type of set up.  I have found some other protocols online that suggest that 50 nm is actually right on the money.  It was stated in the proposal that as long as the wall height was 20 nm or more it should not affect the surfactant adsorption, and the lower the wall height the less it will interfere with the AFM tip when gathering images after surfactant adsorption so 50 nm is actually really good.  I'm a tad nervous because the PMMA solution they have had me using at TU was the same that the group before me was using, which has an expiration date about 4 years ago.  However, it should not cause problems for the purposes we need it for.
I have some trouble making sure that the silicon pieces are microscopically smooth (using the right cleaning solution as well as a plasma cleaner) and this may be what's causing the small imperfection that can be seen in the film.  The debris causing a wake pattern on the surface during the spin coating and I'm not sure it's a problem at this point as we can choose which area to use for the formation of trenches.
I will be returning next Thursday to continue the work and the e-beam tech should be back and we can see if we can get some trenches made!
On the other side of the project, I will be meeting with the OU researcher who has been helping me with nanosphere lithography and discuss the SEM micrographs and hopefully the week after we can try another run of etching with smaller spheres!

Channel Formation

Last week I was able to complete a preliminary sample of a layer of PMMA on silica.  I am still awaiting the results as to how thick the layer was deposited, but hopefully somewhere in the neighborhood of 150 nm (according to the protocol I was attempting to replicate).  I really enjoyed working with the graduate assistants and professors at TU because they were very friendly and helpful.  They could have just have easily left me to my own devices in a foreign laboratory but they helped me find equipment and supplies early one and I was able to figure out the rest as the day went on.  All in all,so far, it has been a pleasant and productive experience and I look forward to continuing my collaboration with them. I will be returning to Tulsa this Thursday to continue the preparation work and when the e-beam technician returns the week afterwards we will be able to form the channels!

Getting somewhere

Going to the University of Tulsa on Thursday to begin preparation on the samples to be used for the trenches samples!!  I'm slightly nervous to be working in another lab, just as I was for coming into the University of Oklahoma I suppose, only this time it's for short spurts.  Every lab has their own house rules that they expect everyone to follow and depending on who is working in the that lab and what else is being performed it can be very different and make beginning work slow.  Because I want to be done with this phase of the research by the end of the summer I am excited that it is moving along but nervous that it may take longer (months) than I want.  I am very confident in the supervisor who will be showing me the ropes there and am looking forward to learning from him and others at TU.  Happy Independence Day!