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.