Towards the controlled CVD growth of graphitic B–C–N atomic layer films: The key role of B–C delivery molecular precursor

Abstract

Graphene-like, ternary system B–C–N atomic layer materials promise highly tunable electronic properties and a plethora of potential applications. However, thus far, experimental synthesis of the B–C–N atomic layers normally yields a microscopic phase-segregated structure consisting of pure C and BN domains. Further, growing the truly ternary B–C–N phase layers with homogenous atomic arrangements has proven to be very challenging. Here, in designing a bettercontrolled process for the chemical vapor deposition (CVD) growth of B–C–N atomic layer films with the minimized C and BN phase segregation, we selected trimethyl borane (TMB), a gaseous organoboron compound with pre-existing B–C bonds, as the molecular precursor to react with ammonia (NH3) gas that serves as the nitrification agent. The use of this unique B–C delivery precursor allows for the successful synthesis of high-quality and large-area B–C–N atomic layer films. Moreover, the TMB/NH3 reactant combination can offer a high level of tunability and control of the overall chemical composition of B–C–N atomic layers by regulating the relative partial pressure of two gaseous reactants. Electrical transport measurements show that a finite energy gap can be opened in the as-grown B–C–N atomic layers and its tunability is essentially dependent on the relative C to BN atomic compositions. On the basis of carefully controlled experiments, we show that the pre-existing B–C bonds in the TMB molecular precursor have played a crucial role in effectively reducing the C and BN phase segregation problem, thereby facilitating the formation of truly ternary B–C–N phase atomic layers.