Interlayer Bound Wannier Excitons in Germanium Sulfide

Materials

LaurentO.Lee Cheong Lem¹  Saskia Fiedler²  Jianbo Sun³  Luca Camilli⁴  Sara Postorino⁴  Maurizia Palummo⁴ 

[1] Australian National Fabrication Facility, Australian National University, Canberra 2601, ACT, Australia;Centre for Nano Optics, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark;Department of Physics, Technical University of Denmark, Ørsteds Plads, 2800 Kgs. Lyngby, Denmark;Dipartimento di Fisica, Università degli studi di Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy;

关键词: germanium sulfide;    cathodoluminescence;    2D materials;    density functional theory;    anisotropy;    many body perturbation theory;   

DOI  :  10.3390/ma13163568

来源: DOAJ

【 摘 要 】

We report a cathodoluminescence (CL) study of layered germanium sulfide (GeS) where we observe a sharp emission peak from flakes covered with a thin hexagonal boron nitride film. GeS is a material that has recently attracted considerable interest due to its emission in the visible region and its strong anisotropy. The measured CL peak is at ~1.69 eV for samples ranging in thickness from 97 nm to 45 nm, where quantum-confinement effects can be excluded. By performing ab initio ground- and excited-state simulations for the bulk compound, we show that the measured optical peak can be unambiguously explained by radiative recombination of the first free bright bound exciton, which is due to a mixing of direct transitions near the $\Gamma$-point of the Brillouin Zone and it is associated to a very large optical anisotropy. The analysis of the corresponding excitonic wave function shows a Wannier–Mott interlayer character, being spread not only in-plane but also out-of-plane.

【 授权许可】

Unknown