Modified MXene: promising electrode materials for constructing Ohmic contacts with MoS2 for electronic device applications

Abstract

The development of MoS₂-based electronic devices is dependent on finding electrode materials suitable for forming Ohmic contacts with MoS₂. For this purpose, we carried out density functional theory and nonequilibrium Green's function calculations to investigate the possibility of using pristine and modified MXene (Ta₂C/Ta₂CF₂/Ta₂C(OH)₂) monolayers as the electrode materials in such devices. These calculations indicated the formation of chemical bonds at the MoS₂/Ta₂C interface, and resulting strong orbital hybridization between the MoS₂ and Ta₂C components, but relatively weak interactions for MoS₂/Ta₂CF₂ and MoS₂/Ta₂C(OH)₂. Ohmic contacts were observed in all three cases. Transport properties were further simulated by modeling two-probe field effect transistors (FETs) with Ta₂C/Ta₂CF₂/Ta₂C(OH)₂ as electrodes. Interestingly, these simulations indicated the formation of Ohmic contacts between Ta₂CF₂/Ta₂C(OH)₂ electrodes and the channel, but an n-type Schottky barrier for the Ta₂C electrode. Furthermore, we found the resistance of the FET based on MoS₂/Ta₂C(OH)₂ to be half of that based on MoS₂/Ta₂CF₂. The results of our study not only revealed promising electrode materials for forming full Ohmic contacts with MoS₂ monolayers in FET devices, but also validated the effective role of a small-molecule fragment as a buffer layer in realizing Ohmic contacts between metal and semiconductor.