Formation of defects in boron nitride by low energy ion bombardment

Abstract

Formation of defects in hexagonal and cubic boron nitride (h-BN and c-BN, respectively) under low-energy argon or nitrogen ion-bombardment has been studied by near-edge x-ray absorption fine structure (NEXAFS) around boron and nitrogen K-edges. Breaking of B–N bonds for both argon and nitrogen bombardment and formation of nitrogen vacancies, VN, has been identified from the B K-edge of both h-BN and c-BN, followed by the formation of molecular nitrogen, N2, at interstitial positions. The presence of N2 produces an additional peak in photoemission spectra around N 1s core level and a sharp resonance in the low-resolution NEXAFS spectra around N K-edge, showing the characteristic vibrational fine structure in high-resolution measurements. In addition, several new peaks within the energy gap of BN, identified by NEXAFS around B and N K-edges, have been assigned to boron or nitrogen interstitials, in good agreement with theoretical predictions. Ion bombardment destroys the cubic phase of c-BN and produces a phase similar to a damaged hexagonal phase.