Kristian Thygesen - Luminescence spectroscopy of point defects in semiconductors

Abstract Point defects are present in all materials and can influence their properties significantly. In most situations the defects are unwanted, but they also have useful applications, e.g. for generation of single photons or magnetic field sensing. I will discuss how density functional theory (DFT), as implemented in the GPAW electronic structure package [1], can be used to calculate various relevant properties of point defects in insulators and semiconductors, from basic thermodynamic properties over the photoluminescence (PL) spectrum to radiative and non-radiative lifetimes of excited states to spin coherence times. I will present a recent first-principles based screening for optically accessible, high-spin point defects in wide band gap 2D crystals [2]. Starting from an initial set of more than 10k point defects, comprising both intrinsic and extrinsic, single and double defects in ten 2D host materials, we identify 610 defects with a triplet ground state, which are analyzed in greater detail. Our approach reveals many new spin defects with narrow PL line shapes and emission frequencies covering a broad spectral range. All the data is made available in the open access QPOD database [3]. References [1]J. Mortensen, A. Larsen, M. Kuisma, A. Ivanov, A. Taghizadeh, A. Peterson, A. Haldar, A. Dohn, C. Schäfer, E. Jónsson, E. Hermes, F. Nilsson, G. Kastlunger, G. Levi, H. Jónsson, H. Häkkinen, J. Fojt, J. Kangsabanik, J. Sødequist, J. Lehtomäki, J. Heske, J. Enkovaara, K. Winther, M. Dulak, M. Melander, M. Ovesen, M. Louhivuori, M. Walter, M. Gjerding, O. Lopez-Acevedo, P. Erhart, R. Warmbier, R. Würdemann, S. Kaappa, S. Latini, T. Boland, T. Bligaard, T. Skovhus, T. Susi, T. Maxson, T. Rossi, X. Chen, Y. Schmerwitz, J. Schiøtz, T. Olsen, K. Jacobsen, K. Thygesen, The Journal of Chemical Physics, 160, (2024) [2]S. Ali, F. Nilsson, S. Manti, F. Bertoldo, J. Mortensen, K. Thygesen, ACS Nano, 17, 21105-21115 (2023) [3]F. Bertoldo, S. Ali, S. Manti, K. Thygesen, npj. Comput. Mater., 8, 56 (2022)