Optical Characterization of Spins and Defects in Thin Films and Heterostructures

This research focused on using optical techniques to characterize of thin film materials, specifically Quantum Point Defect emitters and spin in heterostructures. These are important in the field of spintronics, with possible application in other fields such as quantum information. This research focused on three materials, hexagonal Boron Nitride (hBN), Tungsten Diselenide (WSe2), and graphene. hBN is used in heterostructures, where defects in the lattice are problematic [1]. However, defects in hexagonal Boron Nitride in previous research has been found to be single photon sources [2]. This research focused on learning more about defects in the hBN lattice by making and characterizing defects in hBN. Tungsten Diselenide is a semiconductor that is also used in heterostructures due to its interesting band structure that allows for spin/valley polarization and long spin/valley lifetimes [3]. Graphene, on the other hand, has a short spin/valley lifetime but can transport spins and charge carriers well [4]. These two materials were studied in heterostructures to learn more about the spin movement and interaction between materials. Photoluminescence was taken on both hBN and heterostructures samples. Timeresolved Kerr rotation was used to investigate the spin/valley lifetimes of grapheneWSe2 heterostructures. In hBN, annealing and depositing an atomic layer of Chromium resulted in single photon source peak being found. In the graphene-WSe2 heterostructures, there was a decrease in excitation decay in the graphene overlap region versus the original Tungsten Diselenide flakes, suggesting the movement of spins and electrons from one material into the other.