Tailoring of Bound Exciton Photoluminescence Emission in WS2 Monolayers

• Published in: Physica status solidi. PSS-RRL. Rapid research letters 2020-02, Vol.14 (2), p.n/a
• Main Authors: Kaupmees, Reelika, Grossberg, Maarja, Ney, Marcel, Asaithambi, Aswin, Lorke, Axel, Krustok, Jüri
• Format: Article
• Language: English
• Subjects: Chemical vapor deposition; defects; Emission analysis; Excitons; Mapping; Monolayers; Organic chemistry; Photoluminescence; Temperature dependence; WS2
• ISSN: 1862-6254; 1862-6270
• DOI: 10.1002/pssr.201900355

Temperature‐ and laser power‐dependent photoluminescence (PL) properties of the asymmetric defect‐bound exciton band X D in defective WS2 monolayers, grown by chemical vapor deposition, are studied. Based on PL mapping, a monolayer region with an intensive X D band emission at about 1.9 eV is chosen for further studies. The X D band is thermally quenched above 180 K, and the thermal activation energy is found to be E a  = 33 ± 4 meV. At T = 15 K, the X D band intensity reveals a sublinear dependence with increasing excitation power and the peak position shows a blueshift of about 15 meV per decade of laser power. It is shown that the X D band is related to the deep defect states within the band gap of WS2. Temperature‐ and laser power‐dependent photoluminescence properties of the asymmetric defect‐bound exciton band X D in defective WS2 monolayers, grown by chemical vapor deposition, are studied. Herein, it is proposed that the X D band is related to the deep defects (probably sulfur vacancies), whereas the structural defects and adsorbed atoms can also be the cause of these deep defects.