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.