Stable CoO$_2$ Nanoscrolls with Outstanding Electrical Properties

Layered CoO$_2$ is of great interest for its promising properties but is meta-stable in its bulk form. CoO$_2$ is synthesized by converting the quasi-1D crystal structure of bulk Ca$_3$Co$_2$O$_6$ via a hydrothermal treatment. The resulting nanostructures are predominantly nanoscrolls with very thin walls, which exhibit long-term stability. A detailed structural investigation reveals that the CoO$_2$ is found to crystallize in monoclinic form, similar to the related CaCoO$_2$-CoO$_2$ misfit structure. Individual nanoscrolls are characterized electrically and show a p-type semiconducting nature with a high current-carrying capacity of 4·10$^5$ A cm$^{−2}$ and an extremely high breakdown voltage of up to 270 kV cm$^{−1}$. The results demonstrate the possibility to stabilize meta-stable materials in low-dimensional forms and a promising application of the nanoscrolls as interconnect in high-voltage electronic circuitry.