Electron relaxation and motion at coplanar 1T'/2H MoTe₂ homojunction imaged by time-resolved photoemission electron microscopy

One critical aspect of optoelectronic devices, such as transistors, diodes, and solar cells, is the internal motion of electrons through the interface between semiconductor and electrode. High spatial and temporal resolution imaging the movement of these electrons would provide unprecedented insight into this critical phenomenon. Here, employing the femtosecond time-resolved photoemission electron microscopy with an energy analyzer, we demonstrate imaging of carrier dynamics in space and time after photoexcitation at 1T'/2H MoTe₂ coplanar homojunction, a seamlessly contacted metal/semiconductor interface. The energy-resolved photoelectron images revealed a highly non-equilibrium distribution of photocarriers in space and energy. Combing the time-resolved images, we visualize the motion of electrons from metallic 1T′-MoTe₂ to semiconducting 2H-MoTe₂ within about 1 picosecond. And the carriers lifetime and transfer rate can be obtained from the modified rate equations set for the homojunction. Our findings provide a new insight for the in-plane semiconductor-metal heterostructure, and it will aid the development of future high-performance devices based on 2D materials.