Unveiling the origin of n-type doping of natural MoS2: carbon.

MoS₂ has attracted intense interest in many applications. Natural MoS₂ and field-effect transistors made of it generally exhibit n-type characteristics, but its origin is unknown. Herein, we show that C is the origin of the universal n-type doping of natural MoS₂. Photoemission spectroscopies reveal that while many MoS₂ samples with C detected are n-type, some without C exhibit p-type characteristics. The C-free, p-type MoS₂ changes to n-type over time with the concurrent appearance of C that is out-diffused from bulk, indicating that C induces the n-type doping. The C-origin is verified by C-deposition and supported by theoretical calculations. This carbon appears as nanometer-scale defects frequently observed in scanning tunneling microscopy. In addition, we propose, based on the calculations, that S vacancies are responsible for the p-type characteristics, which contrasts with the widespread belief. This work provides new perspectives on MoS₂ doping and presents a new direction for fabricating reliable MoS₂ devices. [ABSTRACT FROM AUTHOR]