Near-edge x-ray absorption fine structure study of bonding modifications in BN thin films by ion implantation

Abstract

Near-edge x-ray absorption fine structure (NEXAFS) has been used to study the defect content and the bonding modifications induced in BN thin films by ion implantation. The initial films were hexagonal-like BN grown on Si(100) by pulsed laser deposition. Subsequent ion implantation with N2+ at 180 keV induces the formation of a significant proportion of sp3 bonding (cubic-like), and the formation of nitrogen void defects in the remaining sp2 BN. These modifications in the bonding of a film lacking long range order can only be distinguished with a local order technique like NEXAFS.

Point defects in hexagonal BN, BC3 and BCxN compounds studied by x-ray absorption near-edge structure

“…[39][40][41] The X-Z peaks were assigned to a gradual increment of N-vacancies around the B atoms. 25,26 A similar explanation was given in a XANES study of BN nanotubes, while the intense Z peak was suggested to originate from unreacted boron oxide used in the preparation procedure. 42 In another XANES analysis of BN bamboo-like nanotubes and nanothorns, 43 these X-Z p* transitions were assigned to the same N-void defects, but occupied by B in antisite positions.…”

“…Point defects are thus readily formed as result of the regular synthesis processes in an uncontrolled way, but they can be intentionally generated to modify the characteristics of BN, for instance by irradiation. 25,26 In this sense, the production of well-controlled defect arrangements is of great importance for the fabrication of BN structures with defined properties.…”

“…In contrast, h-BN thin films and BN nanomaterials are commonly synthesized outside the thermodynamic equilibrium through processes involving energetic particles (e.g., ions or electrons), what leads to more defective structures. For example, plasmas or directional bombardment of N 2 þ and/or Ar þ ions are often used for h-BN thin film deposition 10,15,17,18,20,[22][23][24][25][26] and BN nanotube formation. 27,28 Also, nanoribbons 29,30 and fullerenes 28,31 of BN have been produced with the help of electron beam irradiation.…”

“…3,13 Highly oriented polycrystalline h-BN bulk samples are also obtained by compressionannealed pyrolysis. 14 Furthermore, CVD [15][16][17][18][19][20] and PVD 10,15,[21][22][23][24][25][26] techniques have been extensively employed to grow h-BN thin films with different degrees of structural disorder. With the advent of nanotechnology, a number of BN nanostructures such as nanotubes, nanoribbons or fullerenes have been successfully produced by chemical or physical methods.…”

Composition and bonding structure of boron nitride B1−xNx thin films grown by ion-beam assisted evaporation

“…First, the B K-edge shows the presence of three peaks (X-Z) at the right of the characteristic h-BN excitonic transition (W), what proves the existence of 1, 2 and 3 oxygen-saturated nitrogen vacancies around B atoms [40,41], respectively. The creation of these N vacancies has been previously described in literature as a result of ion bombardment [42][43][44]. Second, the N K-edge exhibits a sharp peak at 400.9eV assigned to molecular nitrogen, suggesting that N excess in N-rich h-BN might be assimilated in this form.…”