Extended Data Fig. 1: Spectroscopic and transport study of MoS₂ before and after phase change induced by n-butyllithium.

a, Raman spectrum of MoS₂ before and after the phase change induced by n-butyllithium. A new Raman peak around 286 cm⁻¹ was observed after the phase change. b, X-ray photoelectron spectroscopy characterization of MoS₂ samples (Mo 3d_3/2 and Mo 3d_5/2 peaks) before and after the 2H-to-1T/1T′ phase change induced by n-butyllithium. The Mo 3d_3/2 and Mo 3d_5/2 peaks were red-shifted after the phase change. c, I–V transfer characteristics of a MoS₂ field-effect transistor (FET) on a Si wafer capped with 300 nm SiO₂, before and after phase change. The graph shows the drain current as a function of backgate bias for drain voltage V_ds = 50 mV, channel length of 830 nm and channel width of 50 μm. The 300-nm-thick SiO₂ serves as the backgate dielectric layer. Black line, pristine MoS₂ FET; red line, MoS₂ FET after phase change through n-butyllithium treatment; blue line, post-phase-change MoS₂ FET after baking (180 °C for 3 min). The 1T-phase MoS₂ is unstable in air at room temperature, and part of the 1T region is converted into the 1T′ phase. However, the 1T/1T′ mixture MoS₂ retains metallic I–V characteristics after baking.