Enabling mode-locking to take second harmonic generation measurement
Author: Leonardo Landivar Scott | Major: Physics | Semester: Summer 2024
As a Physics major at the Fulbright College of Arts & Sciences, I have had the privilege of conducting research under the mentorship of Dr. Hiro Nakamura in the Department of Physics. This journey, spanning from Summer 2024 to Fall 2024, has been an exhilarating dive into the world of ultra-thin materials. Access to advanced tools, like an atomic force microscope, has let me explore possibilities I never imagined, allowing me to explore the complexity of materials at the nanoscale. Looking forward, I am excited to continue this exploration by adding a nanomaterial minor to my academic path, further delving into this fascinating field.
My research focuses on studying ultra-thin layers of silver iodide (AgI) to understand how the material’s behavior changes when it becomes extremely thin, almost at the atomic level. Using techniques like atomic force microscopy (AFM) and X-ray diffraction (XRD), I’ve been able to study the structure of AgI in this thin form. Understanding these changes is important because it helps us learn more about how materials work when they are pushed to their limits. The challenges I faced, like dealing with limited information and needing very precise equipment, taught me the value of careful and detailed research.
One of the primary challenges has been developing a reliable “recipe” for growing ultra-thin AgI crystals. Achieving the monolayer limit of around 0.5 nm has proven difficult. Although I have managed to produce flakes up to 4.5 nm thick, I need to refine the growth process further to achieve even thinner flakes. To address this, I have systematically varied growth parameters such as temperature and deposition rates, and meticulously recorded the results. This approach has been essential in identifying optimal conditions for crystal growth, though it remains a work in progress.
Another significant challenge has been the precision required for measurements due to the small scale of the samples. Even minor calibration errors can lead to unuseful data in each measurement. To overcome this, I have invested considerable time in learning how to use and calibrate apparatus. Mastering these techniques has been crucial for ensuring accurate measurements and obtaining reliable data from the small-scale crystals and still, it takes me time to get a consistent measurement.
Dr. Nakamura has played a crucial role in helping me refine my experimental techniques. When I struggled with achieving the desired crystal thickness, he suggested adjusting the temperature and deposition distances during growth. His advice led to significant improvements, allowing me to produce thinner and more uniform AgI flakes. Additionally, his feedback on the exciton wavelength shifts helped me identify potential causes such as different crystal structures rather than contamination or oxidation.
I have also received valuable support from Christopher Klenke, my Physics 2 laboratory instructor, and Sudeep Puri, a member of the Nakamura Lab. They taught me how to use and calibrate various characterization tools and assisted with measurements from instruments I did not have access to. Their assistance and collaboration were instrumental in my progress.
This September, I plan to present my findings at the Frontier in Optics and Laser Science Symposium in Denver. I will showcase the thickness achieved by my growth method, the different structures of the AgI crystals, and my ongoing investigation into the exciton shift. I hope to gain valuable feedback, make connections, and expand my knowledge by attending other presentations. While I’m excited, I’m also a bit nervous since it’ll be my first time presenting at an event like this.
Looking ahead, I intend to continue studying the exciton shift, work on reducing the thickness of the flakes, and explore additional characterization techniques. My goal is to complete this research by December and publish an academic paper by the end of the year. This research will also form the basis of my honors thesis.outloutl