First-principles Calculations for the Change of Carrier-type in 2D MoTe₂ by Laser Ilumination

Nowadays, 2D TMD materials, MoTe₂, have emerged as favorable candidates for replacing current Si devices at several nanometer levels with excellent properties for future electronic devices. It is very important to control the carrier-type to make complementary logic devices. There have been many attempts to control the polarity of carriers in 2D MoTe₂, but there have been few reports on the simultaneous implementation of n-type and p-type in a single MoTe₂ nanosheet. Recently, a study has been reported that made a p-n junction diode by selectively converting intrinsic n-type to p-type using laser illumination at 2D MoTe₂ nanosheet with a thinkness of 20-30nm. Raman spectroscopic results showed that Te interstitial and MoO₂ were generated after illumination. However, the exact cause of the carrier-type change by illumination was not clarified. In this study, we have found the stable structures of Te interstitial defects through the first-principles calculations and characterize them in each of the van der Waals gap and surface of MoTe₂. Based on the simulation results, we explain the mechanism that the Te interstitial defect changes the carrier-type in 2D MoTe₂.