Tunable, stable, and reversible n-type doping of MoS₂via thermal treatment in N-methyl-2-pyrrolidone

Here, we report a highly stable and reversible n-type doping of monolayer MoS₂using thermal treatment in N-methyl-2-pyrrolidone (NMP). The Raman and photoluminescence spectroscopic measurements as well as the device performance of the MoS₂transistors suggested a stronger n-type doping effect with increasing time and temperature of the thermal treatment in NMP. Within the given time (5-60 min) and temperature (50 °C-110 °C), the surface treatment in NMP provided an electron concentration from 6 × 10¹⁰to 2 × 10¹²cm^-2. Owing to the n-type doping effect, the thermal treatment in NMP reduced the contact resistance and enhanced the field-effect mobility of the MoS₂transistors. The n-type doping via thermal treatment in NMP remained effective for more than 12 months in ambient air, and could be completely removed after immersion in isopropanol. These results demonstrate that thermal treatment in NMP can be a facile and effective route to achieve stable and reversible doping of two-dimensional materials including MoS₂for their applications in high-performance electronics and optoelectronics.