Bandgap engineering of compound semiconductors and the fabrication of bandgap-modulated heterostructures are important for enabling the development of modern optoelectronics. However, these engineering processes are challenging for two-dimensional (2D) semiconductors of transition metal dichalcogenides, particularly on a large scale. Herein, we report the wafer-scale homogeneous growth of composition-modulated WS2xSe2(1-x) alloys with a continuously tunable bandgap using metal–organic chemical vapor deposition. Well-optimized growth produces monolayer films with excellent homogeneity over the entire wafer. The substitutional atomic chalcogen (S, Se) concentration in WS2xSe2(1-x) alloys is precisely controlled by varying the flow rate of the metal–organic precursors, leading to a bandgap modulation from 1.67 to 2.05 eV, as determined from absorbance spectra. Notably, the optical bandgap of WS2xSe2(1-x) alloys exhibits a nearly linear relationship with the chalcogen composition, implying a low bowing effect. This bowing-alleviated bandgap modulation is attributed to the small lattice mismatch, strain relaxation, and thermodynamic miscibility in the WS2xSe2(1-x) alloys, as confirmed by density-functional theory calculations. Furthermore, the fabrication of hetero-multilayers by stacking differently alloyed films is demonstrated. The produced heterostructure film exhibits a broad spectral absorbance distinct from that of the individual layers. The findings of this study provide insights for the advancement of versatile design of functional 2D optoelectronics.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation (NRF) of Korea grant, funded by the Korean government (MSIT) (2020M3D1A1110548, 2022M3H4A1A01010280, 2017R1A5A1014862 (SRC Program: vdWMRC center), and 2020R1A2C2009389). D.L. acknowledges the support from the NRF of Korea, funded by the Ministry of Education (2020R1I1A1A01071872) and the Korean government (MSIT) (2021R1C1C2094189).
© 2022, The Author(s).
ASJC Scopus subject areas
- Modelling and Simulation
- Materials Science(all)
- Condensed Matter Physics