Formation of BN nanoarches: Possibly the key to cubic boron nitride film growth

Abstract

The formation of epitaxial nanotubes ͑nanoarches͒ on the surface of hexagonal BN ͑h-BN͒ during electron irradiation is reported. In addition to implications in terms of understanding fullerene based structures, we suggest that these act as the nucleation sites for cubic BN ͑c-BN͒ growth and may lead to improved film growth. We also report a strong dependence upon the microscope vacuum, which may be critical in understanding irreproducibility in film growth.

Novel Route to Cubic Boron Nitride Dendritic Nanostructures under Electron Beam Irradiation

“…Such nanoarches may be the center of nucleation for cubic BN growth. Similar nanostructures were also reported by Collazo-Davilla et al [17] under intense electron bombardment. Boulanger et al [18] Figure 3a shows a high-resolution (HR) TEM image of the grown BN nanostructures under electron irradiation, whose chemical composition and structure can be further determined as cubic BN from the corresponding electron energy loss spectroscopy (EELS) spectrum.…”

“…In these particular places, the nature of local bonding becomes sp 3 , as in the case of c-BN. The formation of similar nanostructures was also reported by Collazo-Davilla et al [17] Under electron beam irradiation, momentum transfer from high-energy electrons to the specimen leads to atom displacements into interstitial sites and vacancy formation. The highly curved nanostructures at the edges of the BN crystal should increase due to the introduction of strain or lattice defects induced by electron beam irradiation.…”

Ab initio study of BN nanoarches' surfaces

“…Transmission electron microscope images of electron bombarded hBN samples show that structures like nanoarches appear just before the beginning of cBN nucleation [10]. These nanoarches' surfaces can be understood as quasi onedimensional semi-cylindrical caps grown on the unsaturated edges of the hBN(1 1 2 0) planes.…”

Hexagonal-to-cubic phase transformation in GaN nanowires by Ga+ implantation

“…16 Metastable c-BN is also reported to nucleate with medium/high energy electron or low energy ion irradiation (shallow subsurface implantation; 'subplantation' technique) 17 on h -BN film at room temperature (RT). 18 Most interestingly, phase transformation is observed for graphitic carbon nano-onions to diamond by high energy electron irradiation at slightly elevated temperature (675 K) in absence of pressure or catalyst. 19 In last two cases, the phase transformation falls in the category of incoherent phase transition with two phases containing same element(s) but different crystal symmetry.…”

“…19 In last two cases, the phase transformation falls in the category of incoherent phase transition with two phases containing same element(s) but different crystal symmetry. [17][18][19] Nano-diamond is also reported to form by ion (mixture of Ar, H 2 and CH 4 ) beam irradiation on amorphous carbon film. 20 Ion beam induced stress and possible role of atomic hydrogen/hydrogen ions in stabilizing the sp 3 bonds are discussed as the origin of the phase transformation.…”