Cryogenic Nanobeam Diffraction Reveals Structural Ordering and Defects in MXenes

MXenes, two-dimensional transition metal carbides, and nitrides are notable for their electrical, thermal, and mechanical properties, making them promising for electronics, energy storage, and catalysis. Their surface terminations, organic or inorganic, crucially determine their performance and versatility. However, atomic-scale characterization of these delicate structures is challenging due to MXenes' susceptibility to electron beam damage and environmental degradation.

We employ cryogenic nanobeam diffraction within a four-dimensional scanning transmission electron microscopy framework to overcome these challenges and investigate structural ordering, defects, and moiré patterns in MXenes. Cryogenic conditions minimize beam-induced damage and thermal vibrations, preserving intrinsic structural features and clarifying diffraction patterns. In nanobeam diffraction, a highly convergent nanometer-sized electron probe scans the MXene sample in a raster pattern, recording a two-dimensional diffraction pattern at each position. This generates a four-dimensional dataset capturing real and reciprocal space information, enabling detailed structural analysis. Spatially resolved diffraction patterns allow the identification of local crystallographic variations, such as changes in lattice parameters and orientations.

Our study demonstrates that cryogenic nanobeam diffraction effectively characterizes MXenes' structures while mitigating beam sensitivity and environmental stability issues. The structural insights enhance our understanding of electronic band structures and charge transport mechanisms in MXenes. By elucidating the relationships between lattice defects, moiré patterns, and electronic properties, we enable precise engineering of MXene-based systems with optimized conductivity and carrier mobility. These advancements support the integration of MXenes into next-generation electronic devices, high-performance transistors, and nanoscale quantum materials, advancing condensed matter physics and electronic engineering.