Titanium disulfide as Schottky/ohmic contact for monolayer molybdenum disulfide

Abstract

Abstract2D semiconductors like Molybdenum disulfide (MoS2) still have issues in forming good metal electrode (Schottky and Ohmic) especially for mono layer (ML) to few layers thick due to strain and metallization issues. Here, we explore a 2D semi-metal, titanium disulfide (TiS2), for making different types of contacts with ML MoS2 using density functional theory (DFT). It is observed that ML TiS2 induces ML MoS2 to become p-type with a doping density of 3.85 × 1017 cm−3 which becomes larger with thicker TiS2. Thus, TiS2 can thus be utilized as a variable contact material ohmic if the MoS2 is p-type and as Schottky if the MoS2 is n-type with a Schottky barrier height ranging from 0.3 to 1.35 eV. One of the important results from the study is that compared to a traditional metal–MoS2 in a TiS2–MoS2 contact the bandgap is preserved where in contrast, a traditional metal contact metalizes the monolayer MoS2 and fill its bandgap with states. Hence, a clear path forward to make pristine contacts is to use 2D semi-metals in conjunction with 2D semiconductors.