N-type and p-type molecular doping on monolayer MoS(2)

Monolayer MoS(2) has attracted much attention due to its high on/off current ratio, transparency, and suitability for optoelectronic devices. Surface doping by molecular adsorption has proven to be an effective method to facilitate the usage of MoS(2). However, there are no works available to systematically clarify the effects of the adsorption of F(4)TCNQ, PTCDA, and tetracene on the electronic and optical properties of the material. Therefore, this work elucidated the problem by using density functional theory calculations. We found that the adsorption of F(4)TCNQ and PTCDA turns MoS(2) into a p-type semiconductor, while the tetracene converts MoS(2) into an n-type semiconductor. The occurrence of a new energy level in the conduction band for F(4)TCNQ and PTCDA and the valence band for tetracene reduces the bandgap of the monolayer MoS(2). Besides, the MoS(2)/F(4)TCNQ and MoS(2)/PTCDA systems exhibit an auxiliary optical peak at the long wavelengths of 950 and 850 nm, respectively. Contrastingly, the MoS(2)/tetracene modifies the optical spectrum of the monolayer MoS(2) only in the ultraviolet region. The findings are in good agreement with the experiments.