Supplement Number 1

See the supplementary material for the (1) morphological evolution of AlN on 3 nm h-BN without pretreatment, (2) RSM for the AlN on h-BN/sapphire, (3) thickness measurement of h-BN, (4) AFM images of h-BN with different thickness, (5) Raman spectra of h-BN with different thickness, (6) Raman spectra of h-BN with and without O2 plasma treatment, (7) XPS measurement of h-BN with and without O2 plasma treatment, (8) schematic diagram of AlN growth on h-BN/sapphire, (9) XRD characterization of AlN film before and after exfoliation, (10) KOH etching to characterize AlN film before and after exfoliation.