Defects and deformation of boron nitride nanotubes studied by joint nanoscale mechanical and infrared near-field microscopy

Boron nitride nanotubes (BNNTs) are a one-dimensional material with high mechanical strength, good electric insulation, exceptional thermal conductivity, and high temperature stability. The presence of defects and deformations in BNNTs at the nanoscale affects their mechanical properties. In this article, we jointly utilize nanomechanical characterization and infrared scattering type near-field microscopy on the same individual BNNTs to study the defects and deformations. A characteristic structural defect of BNNT is revealed by a blue-shift of infrared absorption and discontinuity in adhesion. Polygonal facets have been observed in BNNTs, as supported by their mechanical responses and spectroscopic signatures. The presence of polygonal facets implies one should expect reactive chemical and hyperbolic optical properties of BNNTs.