Channel sample preparation

The e-beam is ready to begin use for creating channels to observe the effects of sidewall confinement on adsorption!  Making plans to go to University of Tulsa this week to begin preparing samples so that next week (or the week after depending on scheduling) the e-beam can be used in order to create the channels.
Work to create the nanopillars is still continuing and I am anticipating seeing results after the next etching session which is set tentatively for the week after the fourth of July.  It will be easier, I believe, to move on having both of these samples completed.  I think this because the step afterwards will be to use liquid cell AFM to observe surfactant on the surface of these substrates and focusing on that area, particularly the use of the AFM and developing my skill with it, and not trying to complete the fabrication of another sample will simplify things.  Just happy to know that things are still moving along!  

Taking a small step back can be a good thing

After conferring with one of the research scientists helping me with the etching, the methanol soak may not have removed anything as we had hoped.  It is still looking promising that a sample of nanopillars, usable or not, will be completed before the end of June.  So either way I am to be moving forward, which is good.  On the other hand I am still feeling as though if these don't work or are not up to the specifications that we need them that a lot of time has been ill spent.  Looking on the bright side, it has given me opportunities to learn about what surface we are looking for and look for different approaches at getting it.  In other words, if it does not work then I have a few other options that I can switch to without having to spend more time researching.
I still have not heard back from the contact that has offered to help us with the channels, but with any luck that end of the project will also be up and running by the end of June as well.
As my summer class also come to an end, I'm feeling the pressure from several different sides to produce results and the feeling of being overwhelmed has crept up more than a few times.  However, taking one thing at a time and making sure to manage my time efficiently is definitely keeping me sane.  There is something to be said for a well used day planner.

The Waiting Game

Have been awaiting responses from contacts regarding e-beam lithography and the etching for quite a while now.  I have said it before, but one of the most frustrating things about research is coordinating schedules with more or equally busy people.  To use try and use my time wisely I have continued reading papers about self assembled monolayers and looked for ways to improve the sphere layering techniques I have come up with so far.  The 50 nm beads, while a monolayer, are still the hardest to perfect.  I feel as though there may be some limitations with my set up that prevent the further improvement upon the smallest beads.  However, oxygen etching can be used to shrink spheres that are already on the smaller end of the spectrum (100 nm) to get spheres are 50 or smaller.  The pillars will be spaced further apart if this route is used but that may even work to our advantage in limiting the amount of interaction between sphere monophologies which will be forming on the pillar surfaces.  

I am going to continue trying to reach my contacts in order to move forward as quickly as possible.  In previous posts I have stated my goals for June.  While there is still time to complete these goals, I am currently at the mercy of others and I am not enjoying this goals being at the mercy of the schedules of others.  I will continue working to those goals anyway and make new ones when necessary to work towards getting our questions answered.  

Two birds with One Stone

Having trouble getting responses for the last couple of days.  Have been working on getting 50 nm spheres to create more continuous layers on the silica by changing the solvent ratios some more but to the naked eye there doesn't seem to be any apparent improvement in sample coverage overall.  This does not mean that it is not improving on a micro scale, just that I will need to use an SEM to tell.  This is in the mean time while I have been waiting to hear back from contacts who are graciously helping us with creating the channels (trough) for the other half of the project.  So far though I have not been able to get responses from them or the people who are helping us with the etching to create nanopillars either.  It is a difficult thing to try and schedule something else into an already packed summer for them I'm sure, but it makes me nervous because I don't want to get to a point where I've got more to accomplish than time to do it all.  

As already mentioned the plan is for the troughs to be fabricated in PMMA using e-beam lithography which the group who have been contacted to help us are adept at.  I'm excited to start this because it appears that this technique will be more precise and require less leg work to get a sample ready for surfactant trials.  Once I've gotten to a place where I can get nanopillars done it will essentially be the same deal, where to create a new sample I already have a protocol done, but this is the part where I have to perfect the protocol, and that's where the bulk of the work has gone so far.  As a added benefit from this though I have increased my knowledge of the substrate and its properties, which means that creating this sample will have served a dual purpose, which I look at as an accomplishment. 

Some challenges faced so far

I have been trying to get things started with the e-beam lithography to begin creating the trough structures to look at how adsorption in a channel will occur.  One thing I like about this project is that we are given the opportunity for symmetry.  That is, we are looking at the adsorption of surfactants on the top of small area open surfaces (the terraces) as well as adsorption where the surface is still small but confined.  The difficulty with this is that surfactants are, of course, very small.  Therefore, in order for the effects of the "confinement" to be noticed, or different than any other surface, the surface must be on the order of a few surfactant molecules long or smaller.  That is why this project is so challenging so far is that creating such structures isn't like picking up an x-acto knife and cutting a small piece of substrate.  It must also be smooth and, for the most part, flat so that the size of the surface is the variable causing changes.
Using the smallest size spheres is how these surfaces will be achieved, but the smaller the spheres the harder it is to obtain self assembled monolayers of the beads.  So what we tried with the etching last time is using a small amount of O2 etching along with the primary etchant.  The O2 will shrink the beads linearly with etch time, so the structure formed will (should) have a terrace smaller than the original bead size!
I am really looking forward to working with the e-beam lithography because aside from just being plain cool it will be more precise and repeatable.  Exciting things are happening!! Now if I could only get over this cold....

Sick and Graduate Research Schedule

Was sick for the first part of the weekend.  One thing that is both a blessing a curse about graduate research is that for the most part you dictate your own schedule.  Being sick means that you take off the days you can but you come in an extra day somewhere else to make up the slack.  It is very much reliant on weekly goals to keep on track and make sure things are moving forward.  Therefore I come to work in the morning and leave when I feel that I am no longer productive, no set come in or leave time.  Just try to accomplish what I set out to do for the day and then make a goal for the next day.  My current goal is to try and set up the RIE using PMMA for creating trenches, the opposite of what I have been working on lately.  Will continue to update on the progress of this endeavor.

Methanol Soaking Step

SEM was used to view the state and orientation of the 200 nm spheres on a silica surface.  There was a good amount of monolayer coverage (more than multi-layer), although those monolayers had line interruptions through out it.  A grid was used to find a spot which after soaking was performed could be found again for comparing the sphere positions.
After soaking the silica sample in methanol for 15 hours (overnight) the surface had a much deeper purple color.  When SEM was used to determine whether or not the soaking moved the spheres around significantly, it could be seen that the soaking had little to no effect on the position of the spheres, however not much could be said about the SDS on the sample surface.  From this information we can say that the soaking step can only be helpful, because the sphere positions did not change so if the SDS wasn't removed no harm was done to the sample.  If the SDS film was loosened or removed then when RIE is done there should be less of a mask from the SDS and the spheres should be able to create a better mask for creating the nanopillars.  All this is good news and hopefully next week or the week after, depending on the RIE availability, we will be able to try etching again with a shorter etch time and see what kind of shapes we can get!!  Exciting!!