Cross-sectional transmission electron microscopy studies of boron ion implantation in hexagonal boron nitride

We have reported on the implantation of boron ion into hexagonal boron nitride (h-BN) material to aid the nucleation of cubic boron nitride nanocrystals (nc-BN).Single crystal h-BN was implanted with boron ion at 150 keV at fluences of the order of 1015 and 1017 ions/cm2 at room temperature. High Angle Annular Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM) mapping showed a variation in image contrast in samples irradiated to a fluence of 1 × 1015 ions/cm2. As predicted by Stopping Range and Ions in Materials (SRIM) calculations, the implanted region with the highest damage density appeared to have a bright contrast in HAADF-STEM which represented the high density c-BN symmetry. High Resolution Transmission Electron Microscopy (HRTEM) and electron diffraction measurements showed regions with nc-BN for samples implanted with low fluences and amorphous BN after implantation with high fluences indicating a fluence-related phase transition in BN. Raman spectroscopy showed the emergence of longitudinal optical frequency mode associated with c-BN after implantation. [Display omitted] •Boron ion implantation induces a phase transformation of hexagonal BN to cubic BN.•There exists a threshold fluence above which the material becomes amorphous.•This is a novel study where high angle annular dark field scanning transmission electron microscopy has been used to analyse boron implantation in BN.