  Intercalation is an effective method to improve and modulate properties of
two-dimensional materials. Even so, spatially controlled intercalation at
atomic scale, which is important to introduce and modulated properties, has not
been successful due to difficulties in controlling the diffusion of
intercalants. Here, we show formation of angstrom-wide conductive channels
(~4.3 A) in black phosphorus by Cu intercalation. The atomic structure,
resultant microstructural effects, intercalation mechanism, and local
variations of electronic properties modulated in black phosphorus by Cu
intercalation were investigated extensively by transmission electron microscopy
including in situ observation, DFT calculation, and conductive atomic force
microscopy.
