Fig. 5

Reversible control of optical and electrical properties of MoS₂ via Na⁺ intercalation. a Schematic of the optical measurement. b Gradual reflectance change of MoS₂ on SiO₂/Si via Na⁺ intercalation (spectra offset for visibility). From bottom red line to middle blue line: Na⁺ intercalation; top red line: Na⁺ de-intercalation. c Three cycles of reflectance change of MoS₂ on SiO₂/Si via Na⁺ intercalation. d The potential dependence of source-drain current within three intercalation/de-intercalation cycles. The bias between source and drain was V_SD = 20 mV at room temperature. The potential of MoS₂ was swept from 0 V to −2.6 V and back to 0 V (vs. NaCoO₂ counter electrode) for three cycles at a constant rate of 2 mV s⁻¹. The black and red arrows indicate the sweeping directions. The inset shows the device. Scale bar, 5 µm. e The resistivity of MoS₂ flake (5.5 nm) with standard Hall-bar geometry. The potential of MoS₂ was applied at 300 K. The device was then continuously cooled down to 2 K with fixed voltages. f The corresponding two-dimensional electron densities at different potentials and temperatures. The inset shows the device used in (e) and (f). Scale bar, 5 µm