Fig. : Cross-sectional HRTEM micrograph of the BN film nucleating on AlN buffer layer, grown on a-plane sapphire using TEB as the B precursor for the less ordered film observed in Fig. . Enlarged image to the right of the highlighted section is used to look at the BN basal planes to determine the BN polytype. We observe from the ABAB… stacking of the basal planes that h-BN polytype nucleates on the interlayer above AlN and this continues without any polytype transition. Instead, a rough less ordered phase is observed close to film termination.