Extended Data Fig. 1: Sample fabrication procedure.

a, ABC-stacked domains in mechanically exfoliated trilayer graphene flakes are identified by taking the Raman spectra and extracting the peak maximum corresponding to the 2D mode³². b, ABC-stacked domains are isolated using atomic force microscope based anodic oxidation lithography²⁷. c, The lower part of the heterostructure is assembled on a polypropylene carbonate (PPC) film which is then d, flipped as it is deposited onto the target substrate³³. e, The sample is then vacuum annealed at 375 °C to remove the PPC film under the heterostructure. f, The upper part of the heterostructure, which contains the top graphite gate, trilayer graphene and hBN, is assembled separately and deposited onto the lower part of the heterostructure. g, The top hBN and top graphite gate are etched with XeF₂ followed by O₂ plasma to open windows on the heterostructure, allowing the stacking order to be confirmed after the manipulations of step f. h, The heterostructure is etched with CHF₃ and O₂ plasma and metal is deposited to form electrical contacts. i, Typical Raman spectra of ABA- and ABC-stacked trilayer graphene, centered on the 2D mode. j, Optical micrograph of the trilayer graphene flake used to fabricate Sample A. Scale bar represents 20µm. k, Raman spectrum map of the trilayer graphene flake in panel j. The color represents the peak position of the 2D mode. The scan range is indicated in black dashed line in panel j. The scale bar represents 10µm. l, Optical micrograph of partially processed Sample A. The cyan regions are where the top graphite gate and the hBN on top of it has been etched. Since the bottom gate does not overlap with the etched window, this allows inspection with Raman spectroscopy of the stacking order of the trilayer graphene. The sale bar represents 10µm. The rough location of the actual device is indicated by black dashed line. m, Raman spectrum map of the partially processed Sample A. The region surrounded by a red boundary box remains in ABC-stacking order, which later became the active device region for sample A. n, Optical micrograph of Sample A after fabrication. Scale bar represents 3µm. o, Optical micrograph of Sample B. Scale bar represents 3µm.