The compositional analysis of the films was performed using time-of-flight energy elastic recoil detection analysis (ToF-ERDA). The measurements are done using a 36 MeV 127 I +8 beam. The incidence angle of primary ions and exit angle of recoils were both 67.5° to the sample surface normal constituting a recoil angle is 45°. The measured ToF-ERDA spectra data is then converted into relative atomic concentration profiles using the Potku code. The surface morphology of the sp 2 -BN films was analyzed using scanning electron microscopy (SEM)1550 Gemini. The microscope was operated with conventional and immersion lens (in-lens) secondary electron detectors and an accelerating voltage of 3 kV. Figure shows the FTIR transflectance spectrum on all cuts of sapphire after film deposition. Here, transflectance is the sum of reflectance from the film surface and twice the transmittance through the film. For all investigated samples, we observe the transversal optical in-plane mode peaks for sp 2 -BN at 1369 cm -1 , as well as the longitudinal optical out of plane mode of sp 2 -BN at around 820 cm -1 . Hence, sp -BN films are grown on all studied cuts of sapphire. On these latter bands, sharper absorption bands are observed on the c-cut and a-cut for both the precursors. These sharp edges are suggested to indicate the crystallinity of these samples. Since, for amorphous material there is a variation in the frequency of the vibrational modes which gives broader peaks compared to crystalline films, suggesting that the sp 2 -BN films grown on r-cut and m-cut sapphire are amorphous. originate from sp 2 -BN (000ℓ) and sp 2 -BN (0002ℓ) respectively. AlN (0002) and AlN (0004) peaks are observed for both of these samples as well. The hkiℓ here signifies the long-range order in the direction normal to the surface. Samples with TEB as boron precursor have comparatively lower intensities. From previous studies we know that samples grown using the TMB precursor have higher growth rate of sp 2 -BN and hence more material is deposited during growth which is reflected in the peak intensity. In figures 2(c) and 2(d) there are no BN peaks, confirming the FTIR results that the BN films present are amorphous on r-cut and m-cut sapphire. In figure .e. the r-cut sample shows AlN (112 ̅ 0) growth, this growth orientation on this substrate has been observed seen in past studies and for the m-cut samples in fig. ) AlN( ) and (101 ̅ 3) growth is observed, the latter of which has been reported previously. 32 samples there is twinning of the r-BN expected threefold symmetry which is also observed in previous studies, hence 6 peaks are expected. Since sp 2 -BN diffracts poorly, longer scan times were used for these ɸ-scans which is why a background subtraction and signal smoothening is applied. The low intensity for a few peaks observed is due to the high tilt sensitivity of the sample at higher ɸ angles. Twinning of AlN grown on c-cut Al2O3 is observed. XRD ω-scans on the films grown using TMB provide crystal properties and shows the difference in crystalline quality of the films grown. The a-cut sample shows lower FWHM of 0.985° compared to 1.155° of the c-cut sample which is a difference of about 15%. Further confirming suggestions of a more suitable substrate in a-cut Al2O3 for the growth of sp 2 -BN. Small deviation from the expected ω peak angle suggests very slight buckling in the film surface with respect to the substrate. Broadness of the peaks suggest a less ordered film with respect to the substrate. Samples grown using TMB are compared in the ɸ-scans and ω-scans due to the difference in amount of sp 2 -BN present as described above. Figure . ToF-ERDA analysis is used to calculate the elemental compositions of the samples, (a) Samples grown using TMB precursor (b) Samples grown using TEB precursor. Here the substrates used, Al2O3 (0001), Al2O3 (112 ̅ 0), Al2O3 (11 ̅ 02), Al2O3 (101 ̅ 0) are called c-cut, a-cut, r-cut and m-cut respectively As observed from the ToF-ERDA results in figures 5(a) and 5(b), the samples grown using TEB as the boron precursor show more consistent stoichiometry and a better nitrogen to boron (N/B) ratio compared to the TMB grown samples. For the TEB samples, growth on the c-cut substrates display the least amount of oxygen contamination. Samples grown using TMB as the boron precursor display varying quantities of oxygen in the films, at this stage it is assumed to be a function of the difference in the amount grain boundaries on the films, which leads to oxidation post deposition. The m-cut sample grown using the TMB precursor displays film growth with least amounts of oxygen which could potentially be due to the denser amorphous microstructure on this cut. Looking at the film surface structure would provide further insight (Fig. ). Hydrogen content is very low (<0.2%) and thus omitted. Overall, lower quantities of C and higher quantities of B is seen on the film grown using TEB compared to TMB which agrees with results from past studies. 34 Plan-view SEM micrographs reveal that for the substrates that showed r-BN growth, being the c-cut and a-cut Al2O3 grown using TEB precursor, forms films with previously observed triangular shaped grains of comparable sizes surrounded by a less ordered material with substantial whisker growth. For the samples grown using TMB, the c-cut sample show similar crystal islands but not shaped as consistently as when deposited from TEB. On the a-cut sample, there are no ordered crystals observed on the plan-view, which could be attributed to deposition of disordered material on the topmost layers. The plan-view SEM of sp 2 -BN grown films on the r-cut and m-cut Al2O3 is consistent with the expected amorphous film structure suggested in the XRD (Fig. ) and FTIR (Fig. ) results.