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URSI: Nano Scale Thermodynamics

As engineers design smaller and smaller microprocessors, they need to know how these tiny wafers absorb or reflect light, react to heat and otherwise interact with their environment. That’s why Vassar associate prof. Brian Daly and three of his students are firing lasers at them.

Working under the auspices of the college’s Undergraduate Research Summer Institute (URSI), Daly and his students are conducting a series of tests on tiny sample wafers provided by Intel Corp. They are measuring the heat and vibrations generated on the wafers when the laser beams strike them.

“When the beams hit the surface, its temperature increases and the material expands, creating ripples,” says Mohammed Abdelaziz ’16, one of the three URSI students involved in the project. “And by analyzing the ripples – they’re like a tiny earthquake – we can measure the thickness of the material the laser strikes and the temperature of the surface.”

Daly says the research is necessary because scientists know little about the physical properties of materials at this scale. The samples he and his students are working with this summer are several nanometers – about one-millionth of a centimeter -- thick. “We know what happens to materials on a larger scale, and we know a lot about what happens within atomic particles,” Daly says. “But we don’t know much about nano scale thermodynamics.”

Abdelaziz, a physics major from Queens, and Molly James ’17, a physics major from New Canaan, CT, are working on the project for the first time this summer.  The other member of the team, Sushant Mahat ’16, a physics and biochemistry major from Parbati, Nepal, has been collaborating with Daly since his sophomore year.

James says working in the lab on a single project 40 hours a week has been a much different experience than taking physics courses during the school year. “I’m developing skill sets I never had before – learning how to align lasers, keeping a running log in my lab notebook,” she says. “It changes the way you think about science, doing something in depth that requires you to come up with new and better ways to run your experiment.”

Abdelaziz, James, and Mahat began the project by aligning a series of mirrors and filters that deflect or diffuse the laser beam before it strikes the sample wafers. The wafer is coated with layers of a silicon carbide and aluminum to aid in detecting the heat and vibrations. James says she and her lab partners had to consult some scientific journals on the subject before they could begin to align the mirrors and filters.  “The optics of the experiment were all new to us – we had to spend about a week reading the journals to learn how to analyze the data.”

Abdelaziz says the precision required to set up the experiment was more complex than any work he’d done previously at Vassar. “I took several physics courses during my three years here, but almost all of this lab work is new to me,” he says. “I had worked with simple lasers, but this project is far more complicated than anything I’ve done before. It’s helping me decide what kind of research I want to do when I get to graduate school.”

Mahat says he’s enjoyed the project since he first began working on it three years ago. “It’s been fun, even some of the failures,” he says. “We still don’t know the ultimate outcome of this project, but when you can duplicate your results, that validates all your effort. And I can take what I’ve learned here, confronting a problem and figuring out how to adapt, and apply it to other challenges and problems I confront in other fields of study. It puts you in that mindset: ‘OK, this is a problem; let’s figure it out.’ “

--Larry Hertz

Photos by Buck Lewis