Direct observation of epitaxial alignment of Au on M0S2 at atomic resolution

The morphology and structural stability of metal/2D semic on ductor interfaces strongly affect the performa nee of 2D electronic devices and synergistic catalysis. However, the structural evolution at the interfaces has not been well explored particularly at atomic resolution. In this work, we study the structural evoluti on of Au nan oparticles (NPs) on few-layer MoS2 by high resol utio n transmissi on electro n microscopy (HRTEM) an d quan titative high-angle annular dark field seanning TEM. It is found that in the transition of Au from nan oparticles to den drites, a dynamically epitaxial align ment betwee n Au and MoS2 lattices is formed, and Moirc patter ns can be directly observed in HRTEM images due to the mismatch between Au and M0S2 lattices. This epitaxial alignment can occur in ambient conditions, and can also be accelerated by the irradiation of high-energy electron beam. In situ observation clearly reveals the rotation of Au NPs, the atom migration inside Au NPs, and the transfer of Au atoms between neighboring Au NPs, finally leading to the formation of epitaxially aligned Au dendrites on M0S2. The structural evoluti on of metal/2D semico nductor in terfaces at atomic scale can provide valuable information for the design and fabricatio n of the metal/2D semicon ductorn ano-devices with desired physical and chemical performa nces.