Browsing by Subject "2D materials"

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Anomalous Temperature and Polarization Dependences of Photoluminescence of Metal‐Organic Chemical Vapor Deposition‐Grown GeSe2
(Wiley, 2023-08) Lee, Eunji; Dhakal, Krishna Prasad; Song, Hwayoung; Choi, Heenang; Chung, Taek‐Mo; Oh, Saeyoung; Young Jeong, Hu; Marmolejo‐Tejada, Juan M.; Mosquera, Martín A.; Loc Duong, Dinh; Kang, Kibum; Kim, Jeongyong
Germanium diselenide (GeSe2) is a 2D semiconductor with air stability, a wide bandgap, and anisotropic optical properties. The absorption and photoluminescence (PL) of single-crystalline 2D GeSe2 grown by metal-organic chemical vapor deposition and their dependence on temperature and polarization are studied. The PL spectra exhibit peaks at 2.5 eV (peak A) and 1.8 eV (peak B); peak A displays a strongly polarized emission along the short axis of the crystal, and peak B displays a weak polarization perpendicular to that of peak A. With increasing temperature, peak B shows anomalous behaviors, i.e., an increasing PL energy and intensity. The excitation energy-dependent PL, time-resolved PL, and density functional theory calculations suggest that peak A corresponds to the band-edge transition, whereas peak B originates from the inter-band mid-gap states caused by selenium vacancies passivated by oxygen atoms. The comprehensive study on the PL of single-crystalline GeSe2 sheds light on the origins of light emission in terms of the band structure of anisotropic GeSe2, making it beneficial for the corresponding optoelectronic applications.