Physics - Hitz Graff and Flater

Physics - Hitz Graff and Flater

Quantifying the Wear Properties of a Silicon Oxide/Aluminum Oxide Interface Using an Atomic Force Microscope

Jesse Hitz Graff ’16, Physics

Erin Flater ‘01, Associate Professor of Physics

About the Project

Since the beginning of recorded history, friction has been an important design constraint in human innovation. Engineers must take into account the effects of friction on their materials and designs.

Hitz Graff spent this summer analyzing how silicon oxide wears when it is rubbed on aluminum oxide. Hitz Graff used an atomic force microscope to quantify wear at the nanoscale. The atomic force microscope is an ideal tool for studying surfaces at the nanoscale since it uses a tip whose apex is about 50 nanometers (2,000 times thinner than the width of a human hair).

Project Challenges

“The most difficult part of research in general is figuring out exactly which experiment to perform.” says Flater. ”There are so many variables that control the thing you wish to study. The challenges of scientific research get exacerbated when you study surfaces at the nanoscale. Properties of the surface can change without notice, due to variables out of our control. A little dust or water can significantly change a surface’s friction and wear properties.”

Hitz Graff felt that one major difficulty in this project was avoiding the fracture of the tip during the wearing process. “An essential assumption behind our wear models is that wear of the silicon oxide occurs one atom at a time so any fracture event would greatly skew our results,” he says. “Since the tip we use to conduct the experiments is 2,000 times thinner than a human hair, fracture avoidance proved incredibly difficult but we were able to develop methods to identify fracture events for more accurate interpretation of the data.”

An Interesting Discovery

Since the tip is too small to be viewed optically, it made it necessary to use a special sample of tall and thin spikes (stalagmite type objects) to image the tip in the atomic force microscope.

Ideally every spike on the sample should be the same and give the same image. “Instead, I found that the images vary widely depending on which spike does that imaging,” he says, “We found that the smallest tip images gave the most consistent data. By selecting only those images we vastly improved the accuracy and decreased the uncertainty in our data.”

What They Learned

Hitz Graff says that through this project he discovered the unpredictable nature of scientific research. “Previously I thought that there was a direct correlation between hours spent in the lab and usable data obtained, but that’s far from the truth,” he says, “Some weeks I would spend 50 hours in the lab and feel like I was getting nowhere to have three hours of work the next day result in a major discovery or breakthrough. It’s not a linear trend, it's incredibly sporadic, but that makes it all the more interesting.”

Advice for Students Contemplating Research

Hitz Graff says that it’s important to set goals when starting research, but it's more important to be flexible. “Nothing will ever work out perfectly and if it does then the project was probably too easy to begin with,” he says. “Half the fun of research is adaptation and unexpected results. I feel the best researchers are those who get poor results and find a way to adapt around the problems.”

Flater believes that research is one way to get real-world experience in science. “Research pushes you outside of your comfort zone and teaches you that the scientific principles you encounter in class are just the tip of the iceberg”, she says. “There are so many interesting exceptions to physical ‘laws’ that one gets to discover in research. If you are considering graduate school, it’s a very important experience to have.”

The process of scientific discovery, no matter the practicality or magnitude, is incredibly rewarding. Perhaps 99 percent of your discoveries may never get published or even be worthy of publication, but each new discovery leaves you with knowledge you didn't have at the start, and that's incredibly satisfying.

—Jesse Hitz Graff

Research is often a transformative experience for students because it pushes them to make choices on what to do and how to do it. Research helps students better understand how the messy process of science actually works.

—Erin Flater