Boron carbon nitride nanosheets via induction plasma: Insights on synthesis, characterization, and control of band gap

Abstract

Band gap-controlled two-dimensional boron carbon nitride nanosheets (BCNNS) were synthesized via a scalable one-step thermal plasma-based process near atmospheric pressure. Monotonic change in the band gap of BCNNS from 2.4 to 4.1 eV was achieved through manipulating the carbon loading during the nanosheet formation from ammonia borane and methane. Electron microscopy images showed 2D structures with sizes of 100–200 nm and 1.1–3.7 nm in sheet thickness (3–10 atomic layers). The sheets displayed non-uniformity in layer stacking and dislocation-type defects indicating the inclusion of BN in the C framework. Quasi-uniform distribution of the B/N/C was shown through energy dispersive X-ray spectroscopy. The presence of these elements as well as the sp2 hybridization of the bonding were confirmed using electron energy loss spectroscopy. Fourier Transform infrared spectroscopy showed the presence of B–N/BN, C–N/CN, and C–B/CB groups, and Raman spectroscopy showed progressive graphitization across the BCNNS samples as the BN content is decreased. The optical band gap of various samples is estimated using the Tauc method and found to increase as the carbon content decreased.