Pang Nganthavee, Week 4, All about Ellipsometry! ft. Philly Tour

The fourth week at the Lee Lab began with collecting the last set of data for my first run of making bilayer films. After I finished up spin-coating my last batch of polystyrene-coated silicon wafers with aged silica (t=118h), I went ahead to use the ellipsometer to start measuring the thickness, refractive index, roughness and MSE of my bilayer films. However, this would not be the last time I would be using this machine this week. This was the beginning me basically “hogging” the ellipsometer to measure all my samples for the rest of the week...

After I had finished up my last silica spin-coating session, the initial plan I had in attempting to anneal the polystyrene and silica layers together was by heating my samples up in the vacuum oven. However, as an undergrad at my lab had booked the vacuum oven in the lab’s shared calendar for three consecutive days, my grad student told me that using a hot plate could work as well. Therefore, when I came in on Tuesday, I put my samples - one of each different rpm and aging time - on the hot plate, waited for 4 hours, and then waited again for 30 minutes to allow the films to cool. Finally, my samples changed color from a bluish purple to a having a golden sheen, which in turn indicated that they were ready to measure via ellipsometry.

Annealed films

By putting my bilayer films, in theory, what would happen to them would be the polystyrene penetrating into the interstices of the silica via a process called capillary rise infiltration. Therefore, what I should ideally be seeing while measuring my samples is a decrease in thickness of “Layer #2”, which is the layer of polystyrene, whereas I should be seeing an increase in the thickness of “Layer #3”, which is the layer of polystyrene that has infiltrated into the interstices of the silica.

After I had put my bilayer films on the hot plate, allowed the polystyrene to fill the interstices of the nanoparticle layer via capillary rise infiltration (CaRI), I then had to use the ellipsometer again to see the measurement changes in the values previously mentioned (thickness, refractive index, etc.). Fortunately, the data I was able to collect showed what I had ideally wanted. Whereas the thickness of the top layer of my film increased, the layer below with only polystyrene decreased in thickness. This was an indication that the infiltration had occurred, as the reason explanation for why the thickness of the polystyrene layer decreased was due to the polystyrene itself infiltrating into the interstices of the silica and in turn cause the thickness of the top layer to increase. In addition, another result that I was looking for while measuring was the change in thickness of the top layer of my films. Before I annealed my bilayer films, the top layer only consisted of silica. Now, since the top layer consists of both polystyrene and silica, the thickness should theoretically increase - and fortunately, it did!
Before I was able to move on to analyzing all of the data I had collected from the ellipsometer, there was one last thing I had to do with this machine: measuring porosity. By following what Jyo Lyn had taught me last week on how to measure the porosity of my silica-coated silicon wafers via the liquid cell, I finally completed all of my data collection of this trial run. At that point, as I have collected all the data I needed for the analysis, it marked the beginning my long journey to organize and pair up various sets of data in an attempt to find any sort of trend that they may have with one another.

To end my week at the lab, on Friday, Dr. Peretz and Mr. Sham also paid a visit to everyone who had internships at labs in Philly. As they were visiting 8 students (apparently it’s a record!), only either of them could have made it to each of our labs and in my case, it was Dr. Peretz who visited. She came to meet me at Levine Lobby at around 11:30am, which was actually the lobby of another building. However, since most of the Penn Engineering buildings are connected and plus, the lobby of Levine is much closer to my lab than the Towne Lobby, I thought it would be better to meet at the latter option rather than the former. After she found me waiting in Levine Lobby, I took her for a mini-tour around my lab. Also, just as a side-note, I just realized that I omitted all details about the settings and details of my lab, so I am taking the opportunity to this now as I am describing the tour I gave Dr. Peretz.

I began our tour with showing her the ellipsometer in M44. After explaining about what the machine was able to measure and the significance of certain values of my measurement, I explained that since my lab consists of quite a large number of people, we needed 4 rooms to accommodate us all. In addition to M44, there were two other rooms that were right next to it that just have desks so that people can work on them. After that, I then walked a little bit further down the hallway to show Dr. Peretz M52.

M52 Part 1

M52 Part 2

As M52 was the main lab, it was much bigger than M44, and had a larger range of equipment. After showing the equipments I use a lot over the past 4 weeks at the lab, I ended our mini-tour by showing her the presentation of the data I have compiled so far.

Before we headed over to have lunch with all the other Peddie students who have labs in Philly, although in the emails I exchanged with him, I could sense how busy he was this past Friday, we decided to go knock on Dr. Lee’s door one last time in case he was in his office and could spare a few minutes. Although his door was unfortunately locked when Dr. Peretz and I got there, she said that she understood that he is extremely busy and that it was okay.

When we arrived at White Dog Cafe for lunch, the restaurant was already bustling with a bunch of people waiting in line. Fortunately, Dr. Peretz has made an appointment ahead of time for our party of ten, and after waiting for most of the EXPers and Mr. Sham to arrive, we were seated right away. The food was extremely delicious! I would definitely go there again!

Green Meadow Double Cheddar Burger - the truffle parmesan fries were amazing!  

RPM - The cafe's signature iced tea

Outside the lab, during this past Saturday, Elle decided to come to visit Steph and I in Philly. After we met up, we met to Urban Farmer for lunch, and then decided to go explore the Philadelphia Art Museum for the rest of the day. After we walked around the museum until our legs almost gave out, we ubered back to the area near Steph and I’s apartment for some gourmet doughnuts and bubble tea! Everything was just so delicious!

Our brunch at Urban Farmer!

Me and Steph imitating Rocky.

As for this past Sunday, Steph and I decided that it was time for us to play some tennis to get ready for preseason this coming. Since the more the merrier, we thought that it would be great to invite a few people from her lab. Therefore, Steph decided to invite Felicia, her grad student, and Kyuhyun, a postdoc, to join us for Sunday morning. However, since the Penn courts were reserved for the weekend due to some summer camp and how everyone seemed to come out to play tennis on the weekend at the public courts, we decided that it was unfortunate, but we’ll have to play tennis another day. Instead, however, we did all go to brunch together at Ants Pants cafe. It was a small, little restaurant on the side of the street and when we got there, we surprisingly were seated right away - apparently, according to Felicia and Kyuhyun, the restaurant is usually always crowded and they would usually have to wait 20 minutes to an hour before getting seated!

After we ate brunch, Kyuhyun and Felicia had to go back to their lab to continue working, but since Steph and I were already dressed up and ready to play tennis, we decided that since the courts were so close to the restaurant, it won’t hurt to stop by the courts to see if any were free. When we got there, both of the courts were taken, but since no other “teams” were waiting around for an available court, we decided to stick around for a little while. Fortunately for us, after around 20 minutes of waiting, the couple playing on one of the courts left and we were able to play tennis for the first time in 8 months! From how we played today, our technique and strokes, mine especially, definitely needs some work. However, I can see us coming more often to play tennis at the public courts in the future. I hope that by the time our lab experience comes to an end, our tennis skills would revive and improve enough to help us during preseason this coming fall!

The completion of my fourth week at UPenn marks the halfway point of my lab experience. So far, it has been a lot of fun and people at the lab has been extremely welcoming, as they understand that it will take me some time to get used to this new environment. As of now, I am very much looking forward to see how the last four weeks of my experience at the Lee Lab unfolds, and have even more fun enjoying every moment of it!