Relaxation and transfer of photoexcited electrons at a coplanar few-layer 1 T′/2H-MoTe₂ heterojunction

Fundamental dynamic processes at the electronic contact interface, such as carrier injection and transport, become pivotal and significantly affect device performance. Time-resolved photoemission electron microscopy (TR-PEEM) with high spatiotemporal resolution provides unprecedented abilities of imaging the electron dynamics at the interface. Here, we implement TR-PEEM to investigate the electron dynamics at a coplanar metallic 1 T′-MoTe₂/semiconducting 2H-MoTe₂ heterojunction. We find the non-equilibrium electrons in the 1 T′-MoTe₂ possess higher energy than those in the 2H-MoTe₂. The non-equilibrium photoelectrons collapse and relax to the lower energy levels in the order of picoseconds. The photoexcited electrons transfer from 1 T′-MoTe₂ to 2H-MoTe₂ with at a rate of ~0.8 × 10¹² s⁻¹ (as fast as 1.25 ps). These findings contribute to our understanding of the behavior of photoexcited electrons in heterojunctions and the design of in-plane optoelectronic devices.