Electronic and optical properties of monolayer MoS₂under the influence of polyethyleneimine adsorption and pressure

Abstract

Pressure modifies both electronic and optical properties; however, PEI adsorption only alters the electronic structure of monolayer MoS2.

N-type and p-type molecular doping on monolayer MoS2

“…The concave-downward curve for the bandgap versus the pressure for the MoS 2 system was found to be in good agreement with experiment, 35 while that for the MoS 2 /tetracene is similar to that of an n-type semiconductor, the MoS 2 /PEI interface, in the previous study. 33,36 There is a little difference in the behavior of the bandgap versus the pressure for MoS 2 /F 4 TCNQ and MoS 2 /PTCDA compared to that of the monolayer MoS 2 . That is the bandgap somehow linearly increases to a maximum value and then decreases with more positive pressures.…”

“…The behavior of the optical spectrum of the MoS 2 /tetracene was found to be similar to that of the n-type doping of MoS 2 with PEI. 33 Therefore, the auxiliary peak at a longer wavelength was only found for the monolayer MoS 2 with the p-type doping. 5 Furthermore, as shown in Fig.…”

“…The optimized structural parameters for the monolayer MoS 2 were obtained in the previous publication, 33 where the optimized lattice constant was found to be a = b = 3.18 Å. To explore the adsorption properties of F 4 TCNQ, PTCDA, and tetracene on the monolayer MoS 2 , the geometry of the organic molecules with different configurations was optimized at several adsorption sites on the surface of MoS 2 as shown in Fig.…”

“…S1 and S2 in the ESI. † Therefore, to make a comparison with the previous publication on polyethyleneimine, 33 we will perform a detailed analysis of the geometrical structure, the DOS, and the dielectric function for the parallel configuration of F 4 TCNQ, PTCDA, and tetracene. Furthermore, we also found that the extension of the unit cell size to 6 × 6 and the inclusion of van der Waals correction (using vdW-DF functional) generated more negative adsorption energy (Tables S1 and S2 † ).…”

“…Although the vertical nearest distance increases, the electrostatically attractive force between the adsorbates and MoS 2 increases at a faster rate. 33 Therefore, the adsorption energy becomes more negative. Besides, the interaction of the molecules with the surface is physisorption.…”