Fluorinating hexagonal boron nitride/graphene multilayers into hybrid diamondlike nanofilms with tunable energy gap

Using ab initio calculations and quantum molecular dynamics simulations, we demonstrate that a few layers of graphene sandwiched between hexagonal boron nitride (h-BN) layers can undergo spontaneous transformation into hybrid cubic BN-diamond (c-BN/Dmd) nanofilms upon fluorination. This spontaneous transformation stems from the remarkably higher stability of thin c-BN/Dmd nanofilm with sp³ hybridization over the precursor multilayer with sp² hybridization and is promoted by strong selectivity of fluorination with the boron atoms of the coating BN layers. Upon increasing the total number of multilayers, however, the transformation is no longer spontaneous due to emergence of the energy barrier. Nevertheless, adding more h-BN layers to the hybrid nanofilm can assist the transformation into c-BN/Dmd nanofilms upon fluorination. The electronic properties of the c-BN/Dmd nanofilms can be tuned by controlling the ratio of the BN component and film thickness, which can yield narrow-gap semiconductors for novel electronic applications. In addition, the energy gap in the nanofilms can be modulated linearly by applying external electric fields. © 2011 American Chemical Society.