Yi-Fang interested in epitaxial growth of topological insulator on a variety of substrates by pulsed laser deposition. Understand the relationship between structure and properties, and in particular, the relationship between defects and properties.
We grow theoretically-identified TI materials epitaxially and control residual strains to study systematic changes in the band structure (band crossing at the G-point) for a topologically non-trivial oxide, Sr3SnO (SSO), which can be integrated epitaxially on Si (100) through c-YSZ buffer layer. Since SSO has been predicted theoretically to be TI materials, whose properties would be a strong function of strains and defect microstructures Thin film growth will be pursued using pulsed laser deposition (PLD), strain will be manipulated through substrate selection and deposition conditions, and defects will be introduced through irradiation. We also grow epitaxial Bi2Se3 topological thin film on Si (111) and c-sapphire substrate by PLD, and try to engineer the defects within them to probe how the TI state can be manipulated through strain and low-dimensional defects. Investigate the role of thin film strains and stresses, and interfacial strains, on the electrical and magnetic properties of topological insulators. The equipments that we are using included: X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), High-Resolution Transmission Electron Microscopy (HRTEM), Atomic Force Microscope (AFM), Superconducting Quantum Interference Device (SQUID), Physical Property Measurement System (PPMS), X-ray photoelectron spectroscopy (XPS) and Angle Resolved photoemission spectroscopy (ARPES).
- Y. F. Lee, F. Wu, J. Narayan, and J. Schwartz, ” Oxygen vacancy enhanced room-temperature ferromagnetism in Sr3SnO/c-YSZ/Si (001) heterostructures”, MRS Communucations, 4, 7-13 (2014)
- Y. F. Lee, S. Punugupati, F. Wu,Z. Jin, J. Narayan, and J. Schwartz, ” Evidence for topological surface states in epitaxial Bi2Se3thin film grown by pulsed laser deposition through magneto-transport measurements”, COSSMS, DOI: 10.1016/j.cossms.2014.07.001 (2014)
- S. Rao, Y. F. Lee, J. T. Prater, A.I. Smirnov, and J. Narayan, “Laser annealing induced ferromagnetism in SrTiO3 single crystal”, Appl. Phys. Lett. 105, 17667 (2014)
- F. Lee, F. Wu, R. Kumar, F. Hunte, J. Schwartzand J. Narayan, “ Epitaxial integration of dilute magnetic semiconductor Sr3SnO with Si (001)”, Appl. Phys. Lett. 103, 112101 (2013)
- R. Bayati, J. Ding, Y. F. Lee, R. J. Narayan, J. Narayan, H. Zhou and S. J. Pennycook, “Defect mediated photocatalytic decomposition of 4-chlorophenol on epitaxial rutile thin films under visible and UV illumination” , J. Phys.: Condens. Matter , 24, 395005 (2012)
- C. Lee, Y. F. Lee, M.H. Tseng, C.Y. Huang,* and Y.C. Wu, “Crystal Structure and Ferroelectric Properties of (Bi0.5Na0.5)TiO3–Ba(Zr0.05Ti0.95)O3 Piezoelectric Ceramics”, J. Am. Ceram. Soc. 92  1069–1073 (2009)