Effect of vacancies in monolayer MoS₂ on electronic properties of Mo-MoS₂ contacts

Revealing the influence of intrinsic defects in monolayer MoS₂ on the electronic nature of metal-MoS₂ contacts is particularly critical for their practical use as nanoelectronic devices. This work presents a systematic study toward electronic properties of Mo metal contacts to monolayer MoS₂ with vacancies by using first-principles calculations based on density functional theory. Upon Mo- and S-vacancy formation in monolayer MoS₂, both the height and the width of the tunnel barrier between Mo metal and monolayer MoS₂ are decreased. Additionally, the Schottky barrier of 0.1 eV for the perfect Mo-MoS₂ top contact is reduced to zero for defective ones. The partial density of states near the Fermi level of defective Mo-MoS₂ top contacts is strengthened and electron densities at the interface of defective Mo-MoS₂ top contacts are increased compared with those of the perfect one, suggesting that Mo- and S-vacancies in monolayer MoS₂ have the possibility to improve the electron injection efficiency. Mo-vacancies in monolayer MoS₂ are beneficial to get high quality p-type Mo-MoS₂ contacts, whereas S-vacancies in monolayer MoS₂ are favorable to achieve high quality n-type Mo-MoS₂ contacts. Our findings provide important insights into future design and fabrication of nanoelectronic devices with monolayer MoS₂.