Interfacial Charge Transfer Induced Electronic Property Tuning of MoS_2 by Molecular Functionalization

The modulation of electrical properties of MoS_2 has attracted extensive research interest because of its potential applications in electronic and optoelectronic devices. Herein, interfacial charge transfer induced electronic property tuning of MoS_2 are investigated by in situ ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy measurements. A downward band-bending of MoS_2-related electronic states along with the decreasing work function, which are induced by the electron transfer from Cs overlayers to MoS_2, is observed after the functionalization of MoS_2 with Cs, leading to n-type doping. Meanwhile, when MoS_2 is modified with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F_4-TCNQ), an upward band-bending of MoS_2-related electronic states along with the increasing work function is observed at the interfaces. This is attributed to the electron depletion within MoS_2 due to the strong electron withdrawing property of F_4-TCNQ, indicating p-type doping of MoS_2. Our findings reveal that surface transfer doping is an effective approach for electronic property tuning of MoS_2 and paves the way to optimize its performance in electronic and optoelectronic devices.