Nanostructures of mixed-phase boron nitride via biased microwave plasma-assisted CVD

• Mixed-phase boron nitride nanostructures (BNNSs) prepared via biased MPCVD.
• BNNSs contain amorphous a-BN and crystalline h-BN, t-BN, r-BN, E-BN, w-BN and c-BN.
• BNNSs evolve from dense film to nanocorns and to nanotips.
• BN nanotips result from the combined effects of ion bombardment and plasma etching.

Boron nitride films and nanostructures are deposited by the reaction of B2H6 and NH3 in H2 via biased microwave plasma-assisted chemical vapor deposition. One-dimensional boron nitride nanostructures (BNNSs) are observed on the BN layers by the processing of diamond/BN multilayer under ion-bombardment and plasma etching. At a substrate bias of −100 V, the morphologies of the BNNSs evolve from dense film to nanocorns to nanotips, when the number of the diamond/BN bi-layer increases. Various phases of boron nitride including amorphous-BN, hexagonal h-BN, turbostratic t-BN, rhombohedral r-BN, explosion E-BN, wurtzitic w-BN and cubic c-BN are detected in the BNNSs. The BN nanotips observed are considered to result from the tip structure growth from the combined effects of ion bombardment and plasma etching.