Synthesis of metallic ReO$_{3}$ nanowires

Rhenium trioxide (ReO$_{3})$ is well known as an unusual transition metal oxide with unexpectedly high electrical conductivity close to that of copper. We present the synthesis of highly crystalline metallic rhenium trioxide (ReO$_{3})$ nanowires. ReO$_{3}$ nanowires were grown on a 200 nm silica-covered Si (001) wafer by atmospheric-pressure chemical vapor deposition (APCVD) at about 300 ${^\circ}$ without any catalyst. The wafer was placed in the quartz boat approximately 15 cm downstream from the fine mashed ReO3 powder and heated at 320 ${^\circ}$ with flowing of high purity Ar (500 sccm) for 2 h and then kept at 450 ${^\circ}$ for an additional 3 h. The two-step heating enhanced the growth of ReO$_{3}$ nanowires. The structures and morphologies were examined using scanning electron microscopy (FE-SEM) and high-resolution electron microscopy (HRTEM). Based on HRTEM, the ReO$_{3}$ nanowires exhibit a core of perfect cubic perovskite type single crystal structure with a shell of thin amorphous and disordered structures of less than 2 nm in the near surface layers. Possibly this is due to proton intercalation induced by the surface reaction of single crystal ReO$_{3}$ with water.