First-principles calculations are used to explore the geometry, bonding, and electronic properties of MoS 2 /Ti 2 C and MoS 2 /Ti 2 CY 2 (Y = F and OH) semiconductor/metal contacts. The structure of the interfaces is determined. Strong chemical bonds formed at the MoS 2 /Ti 2 C interface result in additional states next to the Fermi level, which extend over the three atomic layers of MoS 2 and induce a metallic character. The interaction in MoS 2 /Ti 2 CY 2 , on the other hand, is weak and not sensitive to the specific geometry, and the semiconducting nature thus is preserved. The energy level alignment implies weak and strong n-type doping of MoS 2 in MoS 2 /Ti 2 CF 2 and MoS 2 /Ti 2 C(OH) 2 , respectively. The corresponding n-type Schottky barrier heights are 0.85 and 0.26 eV. We show that the MoS 2 /Ti 2 CF 2 interface is close to the Schottky limit. At the MoS 2 /Ti 2 C(OH) 2 interface, we find that a strong dipole due to charge rearrangement induces the Schottky barrier. The present interfaces are well suited for application in all-two-dimensional devices.

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γ-CuI has attracted considerable attention recently as a p-type transparent conductive material. In this paper, we have investigated the hole effective mass, intrinsic defects and group VI-A impurities in γ-CuI by first-principles calculations. We found that the hole effective mass of γ-CuI is light, in line with the high p-type mobility observed in experiments. The p-type conductance is expected to originate from Cu vacancies, which have a low formation energy with no significant n-type compensating defects. The relative high transition level of Cu vacancy, however, may lead to a low hole concentration in the γ-CuI sample. Additionally, no shallow transition levels were found in γ-CuI with substitutional group VI-A impurities at I sites.