In Class Research

May 31, 2019 at 2:27 pm

Alexandra Semposki ǀ Probing Epitaxial Growth and Analysis of Magnetic Bi-layers for Spintronics

By Alexandra Semposki
(B.S. Physics, College of Arts & Sciences, Class of 2019)

Editor’s Note: Alexandra Semposki worked with Dr. Arthur Smith a professor in Physics & Astronomy on a custom molecular beam epitaxy/ low-temperature scanning tunneling microscopy system in his lab. Her summer 2018 project was to investigate nanometerscale magnetic properties of magnetic bi-layers consisting of a ferromagnetic layer on an antiferromagnetic layer, such as Fe/FeMn or MnGa/MnN. To do this, she and graduate student Sneha Upadhyay use MBE to grow nanometer-thin and atomically-flat magnetic bi-layers under vacuum, then transfer them to an adjoining LT-STM chamber in order to scan the as-grown samples using magnetic-coated probe tips.

My summer internship was a continuation of the work I did in the summer 2017 and through the 2017-18 academic year. I assisted graduate student Sneha Upadhyay with her master’s thesis project of growing thin films and analysing them using various techniques for magnetic properties. Of course, this all requires a working knowledge of how the equipment and at least a little bit of the physics works, so I learned more of the lab itself and how to operate it more extensively.

What did I learn? I definitely learned some patience! We had a lot of mishaps and issues as the summer wore on, and I became adept at thinking of solutions to mechanical problems, as well as learning the techniques needed to properly “bake out” vacuum chambers, where we grow our samples, to make sure that the pressure inside is as low as we can get it. I think one of the only ways to really learn everything necessary to run a lab like the one I worked in is to fix everything as each piece breaks down, which is exactly what Sneha and I ended up doing. In addition, Dr. Smith taught me the process of scientific writing and editing, which I am very grateful for, as it will come in handy every day of my life in the future, if I continue in research.

As an undergraduate, it was a challenge to learn about and work on magnetic systems; I asked a lot of questions and read papers as well as books on the subject. I’m still not an expert on any of the physics involved, but I slowly learned a lot over the year I spent in the lab. To triumph over the constant breakdowns of equipment in the lab, we all just had to keep working on fixing those instruments and learning the most we could about them to ensure that they didn’t become faulty again any time soon.

I would meet with Dr Smith whenever we had a topic or an issue we needed to discuss, which was usually once a week or once every two weeks. Sneha and I would give him regular updates on our progress, but longer meetings were less frequent. However, near the end of my research period this past summer, Dr Smith spent a lot more time in the lab’s office working and would check in with us nearly every morning to make sure things were running smoothly.
What intrigues me about the topic is the ability we have when using the Spin Polarised STM to see the little atoms up close in the samples we grow. It amazes me – it brings the infinitesimal to light. I also love being able to see the way that layers of crystals “grow” using the SP-STM and the RHEED systems, the latter of which shows the lattice spacing of the crystalline films we grow, and whether the film is crystalline or not as it grows. Running the equipment and gaining that mechanical knowledge is also a lot of fun and helps one to learn to problem solve very well.

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