Computational study of hafnium metal contacts to monolayer WSe2

In this letter, hafnium (Hf) is evaluated as an alternative contact metal to monolayer tungsten diselenide (WSe2) using first-principles plane-wave pseudopotential method based on density functional theory. Four configurations were considered for Hf-WSe2 top contacts including the bridge, center, top, and upper structures. Results show that Ohmic contact between Hf metal and monolayer WSe2 is formed and that the electron transport across Hf-WSe2 top contacts is mainly of a resonant nature. It is found that the arrangements of Hf metal on monolayer WSe2 play an important role on the energetic and electronic properties of Hf-WSe2 top contacts. The order of interfacial stability of Hf-WSe2 top contacts is upper < top < center < bridge, and Hf-WSe2 top contacts are more stable than Ti-WSe2 top contact because of their small lattice mismatch. The Hf-WSe2 top contact with bridge structure has the highest electron density and the lowest tunnel barrier among the four Hf-WSe2 top contacts. Analysis indicates that Hf metal may be proposed as an alternative electrode material for fabricating top contacts to monolayer WSe2 due to its good stability and low contact resistance.