CVD grown 2D MoS2 layers: A photoluminescence and fluorescence lifetime imaging study

• Published in: Physica status solidi. PSS-RRL. Rapid research letters 2016-11, Vol.10 (11), p.792-796
• Main Authors: Özden, Ayberk, Şar, Hüseyin, Yeltik, Aydan, Madenoğlu, Büşra, Sevik, Cem, Ay, Feridun, Perkgöz, Nihan Kosku
• Format: Article
• Language: English
• Subjects: Chemical vapor deposition; Fluorescence; fluorescence lifetime imaging microscopy; Grain boundaries; Luminescence; MoS2; photoluminescence; Raman spectroscopy; Scientific imaging; two-dimensional materials
• ISSN: 1862-6254; 1862-6270
• DOI: 10.1002/pssr.201600204

In this letter, we report on the fluorescence lifetime imaging and accompanying photoluminescence properties of a chemical vapour deposition (CVD) grown atomically thin material, MoS2. µ‐Raman, µ‐photoluminescence (PL) and fluorescence lifetime imaging microscopy (FLIM) are utilized to probe the fluorescence lifetime and photoluminescence properties of individual flakes of MoS2 films. Usage of these three techniques allows identification of the grown layers, grain boundaries, structural defects and their relative effects on the PL and fluorescence lifetime spectra. Our investigation on individual monolayer flakes reveals a clear increase of the fluorescence lifetime from 0.3 ns to 0.45 ns at the edges with respect to interior region. On the other hand, investigation of the film layer reveals quenching of PL intensity and lifetime at the grain boundaries. These results could be important for applications where the activity of edges is important such as in photocatalytic water splitting. Finally, it has been demonstrated that PL mapping and FLIM are viable techniques for the investigation of the grain‐boundaries. Fluorescence lifetime imaging microscopy (FLIM) measurements are carried out to probe exciton dynamics of CVD grown 2D MoS2 flakes and films. In general, fluorescence lifetimes of these MoS2 flakes are found to be position dependent, where the edges demonstrate a higher lifetime (0.45 ns) than the interior parts of the flakes (0.3 ns). These results are supported with μ‐Raman, μ‐photoluminescence (PL) and atomic force microscopy (AFM) images allowing for a direct correlation between the structural (grain boundaries, structural defects, monolayers and multilayers) and optical properties of 2D MoS2.