Extended Data Fig. 2: High resolution analysis of ZZ-oriented nano-trenches and ZGNRs embedded in h-BN lattices.

a-d, AFM height images of mono-layered ZZ-oriented nano-trenches in h-BN surface by Ni particle-catalyzed cutting. The scale bars are 500, 100, 100 and 200 nm, respectively. The circular inset in (a) shows an atomic-resolution friction image of the h-BN. All the trenches are found along ZZ direction. b,c, show nano-trenches narrower than 5 nm. d, For a ~ 78 nm-wide trench, the depth profile shows that etching occurs only at the top layer of h-BN substrate. e-h, AFM height images of GNRs embedded in the ZZ-oriented nano-trenches. The width of ZGNRs is less than 10 nm. The scale bars are 500, 200, 100 and 100 nm, respectively. i, A STEM MAADF-α×HAADF image for a ZGNR sample. The scale bar is 200 nm. j, A zoomed-in MAADF image of a region shown in the middle of white dashed frame in (i). The scale bar is 10 nm. k, A Wiener-filtered MAADF image of the region shown in the dashed frame in j, The STEM investigation indicates that the boundaries between GNR and h-BN can be distinguished with a scale bar of 2 nm. The measured in-plane width of the GNR is ~3.2 nm.