Unidirectional domain growth of hexagonal boron nitride thin films

Two-dimensional van der Waals (2D-vdW) layered hexagonal boron nitride (h-BN) has gained tremendous research interest over recent years due to its unconventional domain growth morphology, fascinating properties and application potentials as an excellent dielectric layer for 2D-based nano-electronics. However, the unidirectional of h-BN thin films directly on insulating substrates remains significantly challenging because high-bonding anisotropicity complex kinetics than conventional growth, thus resulting in formation randomly oriented domains hindering usefulness integrated nano-devices. Here, ultra-wide bandgap are grown low-miscut atomically smooth highly c-plane sapphire (without using any metal catalytic layer) by pulsed laser deposition, showing remarkable triangular-shape morphology. This is attributed step-edge guided nucleation caused reducing film-substrate interfacial symmetry energy, thereby breaking degeneracy sites random domains, revealed density functional theory (DFT) calculations. Through extensive characterizations, we further demonstrate single crystal-like films. Our findings might pave way feasible large-area direct electronic-quality high-performance 2D-electronics, addition would be beneficial hetero engineering 2D-vdW materials with emergent phenomena.