Simulation study of Fermi level depinning in metal-MoS2 contacts

Engineering of metal-MoS2 contacts to overcome Fermi level pinning

“…Indeed, our procedure prevents the formation of charge dipoles inside the metal crystal. In [17] we demonstrated that a non-completely relaxed structure may lead to overlooked artifacts in the dipole analysis and in the calculations of the SBH in metal-MoS2 contacts.…”

“…In this work, we made use of the DFT methodology, as implemented in the Quantum ESPRESSO suite, to study the MoS 2 in contact with aluminum (Al), gold (Au) and palladium (Pd) [17,18]. For these three contact options, we produced supercells sandwiching a MoS2 monolayer with a metal crystal formed by six layers of metal atoms as sketched in Fig.…”

“…1), we matched the 111-surface of a six-layer metal crystal to a √3 × √3 supercell for the monolayer MoS2 [15]. Then, we also used relaxation to reduce residual forces on atoms [22] and, in particular, we relaxed the position of all the atoms in the system [17]. We believe that this approach is more dependable than some procedures previously reported in the literature, where the position of the four top metal layers were instead fixed and the relaxation was involved only the metal layers close to the MoS2 semiconductor [14,15].…”

“…However, the applied F values depicted in Fig. 7 are not sufficient to zero the SBH for holes (a) and more negative electric fields are required to ease the contact to the VB of the MoS2 [17]. In order to improve the understanding of the physical mechanism responsible for the observed EF shift, we extracted the charge induced by F in the MoS2 layer.…”

“…Indeed, for d = 0.8 nm, a dependable F value can be determined at both sides of MoS2 from the potential energy profile (see Fig. 7 of [17]). The charges extracted by means of the Bader analysis or the Gauss law agree well for both the MoS2-Al [Fig.…”