Colloquium: Guangfu Luo

ABSTRACT: Accurate control over the growth and defects of functional materials at the atomic level is a major goal of materials science. However, such control is usually difficult to obtain even with state-of-the-art experimental methods. In this talk, I will demonstrate that highly accurate ab initio computations can significantly alleviate this challenge by uncovering the atomic-level mechanisms and providing rationally-revised synthesis routes. I will first present our discovery of dynamic swapping mechanisms that prevail in the growth of both Ruddlesden-Popper oxides [1] and GaAsBi alloys [2]. Understanding of these critical growth mechanisms has helped us gain more control in the growth of these two classes of materials. Next, I will present our findings on the defects that seriously jeopardize the electronic and optical properties of GaAsBi alloys [3]. This study provides valuable guidance on how to reduce the defects in GaAsBi alloys, which have inhibited their successful applications for years. Finally, I will briefly discuss our surprising discovery of a long-standing issue in the simulation of transition states. This discovery was inspired by the defect study [3] and is expected to influence the theoretical prediction of dynamics in a number of fields.

[1] J. H. Lee*, G. Luo*, I. C. Tung, S. H. Chang, Z. Luo, M. Malshe, M. Gadre, A. Bhattacharya, S. M. Nakhmanson, J. A. Eastman, H. Hong, J. Jellinek, D. Morgan, D. D. Fong, and J. W. Freeland, “Dynamic layer rearrangement during growth of layered oxide films by molecular beam epitaxy”, Nature Materials 13, 879 (2014). *equal contribution

[2] G. Luo, S. Yang, J. Li, M. Arjmand, I. Szlufarska, A. S. Brown, T. F. Kuech, D. Morgan, “First-principles studies on molecular beam epitaxy growth of GaAs_1-xBi_x”, Physical Review B 92, 035415 (2015).

[3]G. Luo, S. Yang, G. Jenness, Z. Song, T. F. Kuech, D. Morgan, "Understanding and reducing deleterious defects in the metastable alloy GaAsBi", NPG Asia Materials, 9, e345 (2017).