Colloidal Molybdenum Diselenide Nanocrystals for Tunable, Broadband, and Mixed-Dimensional Photodetectors

• Published in: ACS applied nano materials Vol. 4; no. 2; pp. 1877 - 1885
• Main Authors: Jana, Subhajit, Ray, Samriddha, Mukherjee, Subhrajit
• Format: Journal Article
• Language: English
• Published: American Chemical Society 26-02-2021
• Subjects: photodetectors; molybdenum diselenide; 2D nanocrystals; 2D material; heterostructure
• ISSN: 2574-0970; 2574-0970
• DOI: 10.1021/acsanm.0c03253

Two-dimensional (2D) semiconductors with a direct band gap are attractive for the fabrication of 2D/Si heterostructures for complementary metal–oxide–semiconductor compatible nanophotonic devices. We report the characteristics of sonochemically exfoliated molybdenum diselenide (MoSe2) nanocrystals (NCs) integrated on large-area Si platforms to demonstrate tunable and broadband heterojunction photodetectors. The exfoliation of bulk materials to the 2H-semiconducting phase of MoSe2 NCs exhibiting excitonic absorption peaks with characteristic 2D nature is established. A gradual blue shift in the absorption peaks accompanied by the stiffening of A1g Raman mode supports the size-dependent properties of NCs. Spectral response of MoSe2-NCs/Si (2D/3D) heterojunction devices reveal size-tunable and broadband (400–1400 nm) photoresponse, with the optimum sample (size ∼12 nm) showing a peak responsivity and a detectivity of ∼960 mA/W and ∼1.8 × 1012 Jones, respectively, at a low bias (−2 V).