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SUMMARY:EELS and Optical Properties of Layered and 2D Materials - Shangpen
 g Gao
DTSTART:20240731T130000Z
DTEND:20240731T143000Z
UID:TALK219424@talks.cam.ac.uk
CONTACT:Bo Peng
DESCRIPTION:I will start by reviewing our recent work applying electron en
 ergy-loss spectroscopy (EELS) simulations to materials characterization an
 d electronic structure research. By combining experimental (S)TEM-EELS wit
 h simulations\, we mapped the electronic states attributed to specific uno
 ccupied pz orbitals around a fourfold-coordinated silicon point defect in 
 graphene [1] and confirmed the existence of a new layered hexagonal crysta
 l: h-BeO [2]. Our study reveals the unusual bonding characteristics of fiv
 efold-coordinated structures (h-AlN and h-MgO) with planar AB honeycombs\,
  highlighting a “missing π” character [3].\n\nNext\, I will introduce
  an effective method to accurately predict the dielectric and optical prop
 erties of 2D materials by restoring their intrinsic dielectric functions i
 ndependently of the additional vacuum spacing employed in supercell calcul
 ations. Using this method\, we evaluated the momentum- and thickness-depen
 dent excitonic and plasmonic properties of 2D h-BN and MoS2 [4\,5].\n\nLas
 tly\, I will demonstrate how DFT calculations of stress-dependent formatio
 n energies and migration energies of vacancies and self-interstitials can 
 aid in growing perfect single-crystal silicon ingots for the semiconductor
  industry [6].\n\nReferences:\n\n[1] M. Q. Xu\, A. W. Li\, S. J. Pennycook
 \, S. P. Gao\, W. Zhou. Physical Review Letters 131: 186202 (2023)\n\n[2] 
 L. F. Wang\, L. Liu\, J. Chen\, et al. Angewandte Chemie International Edi
 tion 59(36): 15734–15740 (2020)\n\n[3] A. A. Sun\, S. P. Gao\, G. Gu. Ch
 emical Science 11(17): 4340-4350 (2020)\n\n[4] G. Yang\, S. P. Gao. Nanosc
 ale 13: 17057 (2021)\n\n[5] G. Yang\, J. C. Fan\, S. P. Gao. Nanoscale Adv
 ances 5: 6990–6998 (2023)\n\n[6] H. J. Hu\, Z. R. He\, Y. Pei\, et al. C
 rystal Growth & Design. In press. https://doi.org/10.1021/acs.cgd.4c00164
LOCATION:TCM Seminar Room
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