Computational Analysis of Metal Contact on Bi2O2Se with Se Surface Vacancies

In this work, a theoretical study on the electronic properties of the metal/Bi2O2Se interface is presented through the density functional theory calculation. Particularly, the effects of Cr, Pd, Pt, Au, and Bi on monolayer, bilayer, and trilayer Bi2O2Se are explored. Naturally created Se vacancies on the Bi2O2Se surface are also considered by constructing two interface structures: the metal/Bi2O2Se with the Se vacancies remaining or filled with metals. For the metal/monolayer Bi2O2Se, it is observed that the Bi2O2Se layer is fully metallized since Bi2O2Se strongly interacts with the metal. Meanwhile, for the metal/bilayer and trilayer Bi2O2Se, the Bi2O2Se layers remain semiconducting except for the layer right next to metal. Among the considered metals, regardless of whether the Se vacancies are filled with metal or not, the semiconducting layers in bilayer and trilayer Bi2O2Se form Ohmic contact with Bi. It is also found that filling the Se vacancies with the metals heavier than Se increases the interface distance between metal and Bi2O2Se, and hence results in the weak Fermi level pinning effect.