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Vibronic fine structure in high-resolution x-ray absorption spectra from boron nitride nanotubes

We have applied the high-resolution near-edge x-ray absorption fine structure (NEXAFS) measurements around the nitrogen K- edge to study vibrational effects in ion bombarded boron nitride nanotubes (BNNTs). Different fine structures have been observed in surface sensitive partial electron yield (PEY) and bulk sensitive total electron yield (TEY) spectra. The PEY structure is assigned to NO molecules, present close to the surface, and interpreted as vibronic coupling to electronic core excitations. Low energy ion bombardment promotes the creation of NO as broken B-N bonds are replaced by N-O bonds involving oxygen from BNNT surface. In contrast to PEY, the bulk sensitive TEY measurements on ion- bombarded samples show a clear vibronic signature of molecular nitrogen formed below the surface at the depth corresponding to the projected range of bombarding ions.

Boron nitride nanotubes; NEXAFS; vibronic structure; defects

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