Spatial Resolution Improvements using Collimation Methods and their Applications

Student’s Name: Elizabeth Peng Home Institution: Princeton University NNCI Site: ShyNE @ Northwestern University REU Principal Investigator: Dr. Michael Bedzyk, Materials Science and Engineering, Northwestern University REU Mentors: William Mah and Professor Sumit Kewalramani, Materials Science and Engineering, Northwestern University Abstract: Thin films are used in various fields, including catalysis, sensors, and semiconductor electronics. To identify their potential applications, scientists seek to understand their structural properties. Several techniques for thin film characterization involve the use of x-ray diffraction off of crystalline planes. The X-ray beams yield specific intensity patterns due to how they scatter from these plane interactions. This work focuses on the properties of single crystal thin films grown via pulsed laser deposition. High-resolution X-ray diffraction (XRD), X-ray reflectivity (XRR), and in-plane Grazing Incidence Wide-angle X-ray diffraction (GIXRD) scans were done to evaluate film characteristics such as thickness, roughness, electron density, etc. In addition, we are now exploring how to expedite this data collection using the full 2D capabilities of the area detectors. This will enable the capture of multiple diffraction peaks in one shot from polycrystalline samples or collect fast XRR and reciprocal space maps in principle. However, this requires the beam to be small and collimated in both directions normal to beam propagation. Currently, the X-ray source is a line source. To resolve this, we are applying collimation slits to convert the linear x-ray source to a point. This results in decreased incident intensity. We are trying to determine whether data collection using the 2D detector is more efficient than the 0D detector and compare the 2D detector’s relative effectiveness given its loss in intensity. We are also using 2D reciprocal space mapping to determine the relative position of Bragg peaks, which will inform a film’s strain and mosaicity. Our findings will provide valuable insights into optimizing X-ray characterization techniques for thin films, enhancing the understanding of their structural properties for various applications.