Fig. 2

Time evolution of conversion from MoS₂ to MoTe₂. a Optical images and the corresponding schematics of the initial growth stages: 5, 10, and 15 min. The dark color indicates the fully converted MoTe₂ region from MoS₂. Conversion is favored at the edges and grain boundaries; scale bars, 50 μm. b Amplified optical image of the sample grown for 15 min. The MoS₂ flake is completely converted to MoTe₂ in the yellow-dotted circle; scale bars, 50 μm. c, d XPS mapping image of tellurized MoS₂ flake for S 2p_3/2 (c) and Te 3d_5/2 (d) in the white-dotted square in b; scale bars, 30 μm. A high Te content was detected in the dark region (no sulfur content was detected), while the S content (~ 20%) is seen in the bright region. e Raman spectra of bright and dark regions. The dark region shows the Raman spectrum exclusively from MoTe₂ (1T′−2H mixed phase). Some unknown peaks (349 and 435 cm⁻¹ in red circles) in the bright region, which are far from MoS₂ and MoTe₂ Raman peaks are observed