Electron microscopy study of the shell geometry in bent and twisted GaAs-InP core-shell nanowires.

The spontaneous bending of core-shell nanowires through asymmetric shell deposition has implications for sensors, enabling both parallel fabrication and creating advantageous out-of-plane nanowire sensor geometries. This study investigates the impact of shell deposition geometry on the shell distribution and bending of GaAs-InP core-shell nanowires. Scanning and transmission electron microscopy methods are employed to quantify nanowire twisting and bending. A practical analytical electron tomography reconstruction technique is developed for characterizing the nanowire shell distribution, which utilizes the hexagonal nanowire shape to reconstruct two-dimensional cross-sections along the nanowire length. The study reveals that the orientation of the phosphorus beam with respect to the nanowire side facets induces significant variations in nanowire bending and twisting. The findings demonstrate the important role of crystallographic orientation during core-shell nanowire synthesis for engineering the shape of bent nanowire sensors.