Fig. 1.

Alkali-metal-assisted conversion from MoS₂ to MoTe₂. a Schematic of the Na-assisted tellurization process. MoS₂ was flipped over to face the NaOH-coated substrate. b Illustration for the conversion step from Mo–S to Mo–Te via a Na-scooter. Na₂Te, which is regarded as the most probable Na–Te compound from sodium hydroxide, plays a role as the Te carrier and catalyst for exchanging with S atoms. After exchanging S atoms with Te atoms, Na₂S is converted to Na₂Te under Te-rich conditions. c Gibbs free energy changes for conversion without/with Na-scooter. ∆G is reduced to around 70 kJ mol⁻¹. d, e Raman spectra (d) and XPS taken for Mo, S, and Te (e) of partially tellurized MoS_2−xTe_x without/with Na-scooter at 600 °C for 30 min