Thermal CVD synthesis of carbon nanotubes filled with single-crystalline Cu nanoneedles at tips

Carbon nanotubes (CNTs) filled with Cu nanoneedles at tips have been synthesized using alkali-element doped Cu catalyst by a simple thermal chemical vapor deposition method. X-ray diffraction analysis reveals that Cu nanoneedles have perfect face-centered cubic structure. The carbon shells provide an effective barrier against oxidation and consequently ensure a long-term stability of the Cu core. Selected area electron diffraction indicates that these Cu nanoneedles are single crystalline with fine quality. Transmission electron microscopy and high-resolution transmission electron microscopy were employed to analyze the microstructure of Cu filled CNTs. On the basis of experimental results, a simple growth model is proposed in this paper.