Influence of growth duration on size and morphology of boron nitride nanotubes grown via chemical vapor deposition technique

Boron nitride nanotubes are synthesized on Si substrate via a chemical vapor deposition technique with different growth durations. Field emission scanning electron microscopy micrographs show a clear influence of growth duration on size and morphology of the synthesized nanotubes. It reveals that the diameter of the tubes decreases and length increases with an increase in growth duration. Total diameter of the tube has been reduced up to 31% and length increased up to 30% with an increase of 20 min growth duration. As a result, morphology of nanotubes has also been changed from curve like to straight. Transmission electron microscope confirms the tubular structure of the synthesized nanotubes with an interlayer spacing of 0.34 nm that corresponds to d(002) plane of hexagonal boron nitride and its crystalline nature. Energy dispersive X-ray spectroscopy indicates the presence of magnesium particles in the synthesized samples that refers to its catalytic growth. X-ray photoelectron spectroscopy confirms the elemental compositions of the sample. Raman spectra reveal a peak shift of 5.48 cm−1 towards higher region of wavelength that corresponds to E2g mode of vibration in hexagonal boron nitride. This result also confirms the structural change in the synthesized boron nitride nanotubes with respect to the growth duration.