Tuning the electronic properties of Ti-MoS₂ contacts through introducing vacancies in monolayer MoS₂

The effect of vacancies in monolayer MoS₂ on the electronic properties of a Ti-MoS₂ top contact has been investigated using first-principles calculations. A Mo-vacancy is easier to form than a S-vacancy in a Ti-MoS₂ top contact, especially under oxidation conditions. A Mo-vacancy eliminates the Schottky barrier of the Ti-MoS₂ top contact, and a S-vacancy reduces the Schottky barrier from 0.28 to 0.15 eV. Mo-vacancies are beneficial for obtaining a high quality p-type Ti-MoS₂ top contact, whereas S-vacancies are favorable to achieve a high quality n-type Ti-MoS₂ top contact. Moreover, defective Ti-MoS₂ top contacts have stronger dipole layers, a higher potential step and more transferred charges than a perfect ones. The electronic properties of Ti-MoS₂ top contacts can be tuned by intrinsic vacancies in monolayer MoS₂. Our findings provide important insights into the future design and fabrication of novel nanoelectronic devices with monolayer MoS₂.