Ohmic contacts of monolayer Tl2O field-effect transistors

Monolayer (ML) Tl 2 O, as a newly discovered metal-shrouded two-dimensional semiconductor with an appropriate bandgap and high carrier mobility, is a promising candidate as the channel materials for the next-generation field-effect transistors (FETs). Using ab initio electronic structure calculation and quantum transport simulation, the contact properties of ML Tl 2 O–metal interfaces based on FET are comprehensively investigated with Au, Sc, Tl, Ni, graphene, Ti 2 C, Ti 2 CF 2 , and Ti 2 C(OH) 2 electrodes. ML Tl 2 O undergoes metallization with Au, Sc, Tl, Ni, and Ti 2 C, while it forms van der Waals-type contact with graphene, Ti 2 CF 2 , and Ti 2 C(OH) 2 . An n -type lateral Schottky contact is formed with Ni, Au, Sc, and Ti 2 C electrodes with the electron Schottky barrier height (SBH) of 0.25, 0.27, 0.27, and 0.36 eV, respectively, while a p -type lateral Schottky contact is formed with graphene electrode with the hole SBH of 0.10 eV. Surprisingly, a desired n -type Ohmic contact arises with Tl and Ti 2 C(OH) 2 electrodes and a desired p -type Ohmic contact arises with Ti 2 CF 2 electrode. The study not only provides a deep understanding of the interfacial properties of the ML Tl 2 O FETs but also reveals a versatile approach to realize both n - and p -type Ohmic contact for the ML Tl 2 O FETs.