Figure 4: Construction of graphene/h-BNC/h-BN in-plane 2D heterostructures.

(a–d) Schematics of the spatially controlled conversion process of graphene into h-BN. (a) Transfer graphene onto a high-resistance intrinsic silicon wafer as a media substrate. (b) Deposit 50 nm SiO₂ with predefined patterns on top of the graphene. (c) Transfer the whole chip into a CVD (chemical vapour deposition) furnace for conversions. (d) Wash away the SiO₂ masks by buffered HF solutions and transfer the films via PMMA-KOH lift-offs onto other substrates. (a), (b) and (e–h) Two-step process that converts graphene into a graphene/h-BNC/h-BN heterostructure thin film. The first cycle (a,b) is identical to the steps explained previously, except that it stops at a partial-substitution intermediate state. (e) h-BNC surrounds a mask-protected graphene region. The second cycle starts with a new mask that protects regions where h-BNC needs to be preserved (f), and finishes the conversion until a perfect h-BN film is formed in the defined region (g,h). (i) Schematic of graphene/h-BN strip. (j) Optical image of graphene/h-BN alternative strips on SiO₂ substrate with a scale bar 10 μm. (k) Raman mapping at 2D peak (2,700 cm⁻¹) of the marked area in (j) (scale bar, 5 μm). (l) Schematic showing the proposed atomic structure of a graphene/BNC/h-BN strip. (m) Optical image of graphene/h-BNC/h-BN alterative strips synthesized by this two-step conversion with a scale bar 40 μm. Raman mapping of the squared area from the 2D peak (2,700 cm⁻¹) is shown in (n) (scale bar 10 μm).