Controllable crystal restructuring in MXene by electron irradiation.

Recent decades have witnessed the breakthroughs in utilizing electron beams as the smallest tools to tailor materials. Whereas, the manipulation of atoms in a controllable manner by the electron beams is a long-time challenge due to the random nature of atom-knock-on. Here, we show that electron irradiation can controllably manipulate atoms in newly-developed MXene multilayers. The multilayers consist of many few-atom-thick transition metal carbide slabs that are terminated with hydroxyl and O functional groups on each slab. Upon electron irradiation, the H atoms of the hydroxyl are knocked off, creating cation traps surrounded by dangling O confined in a nano-sized slit. Simultaneously, the transition metal atoms partially struck away from the carbide slabs migrate into the cation traps periodically, resulting in crystal restructuring. Crystal restructuring is versatile for various MXenes and dramatically improves the electric conductivity and lessens the anisotropy, holding significant implications in engineering MXenes at the atomic scale.