Triggering Thermal Healing of Large Area MOCVD Grown TMDs at the Trion Dissociation

Abstract

Overcoming the thermal sensitivity of the van-der Waals layered material, an inevitable high defect concentration in a large area (2 x 2 cm(2)) vapor phase grown few-layer MoS2 (2.3 nm thick) is uniformly repaired over the entire area through thermal process. The defect concentration of the healed sample decreased by 3.8 times, and both the PL intensity and field-effect mobility over the entire area increased by more than two times. Through observing in situ photoluminescence (PL) spectra with raising temperature, it is confirmed that the oxygen-substitutional healing proceeds radically from the starting point at which trion dissociation energy is zero, inducing e-h plasma. At this time, for achieving successful healing of the entire area, immediate cooling is required to prevent accelerated oxidation when reaching the critical temperature. Considering the laboratory-dependent crystalline quality of vapor-phase grown transition metal dichalcogenides (TMDs), the methodology to find the optimal thermal healing temperature through in situ PL monitoring will be quite useful.