Fig. 1. Growth and atomic-scale characterization of borophene sheets.

Schematics of (A) distorted B₇ cluster and (B) growth setup with atomic structure model and STM topography rendering. (C) AES spectra of clean Ag(111) before and after boron deposition. (D to I) Series of large-scale STM topography (left) and closed-loop dI/dV (right) images of borophene sheets, showing (D and E) low coverage (V_sample = 2.0 V, I_t = 100 pA), (F and G) medium coverage (V_sample = 3.5 V, I_t = 100 pA), and (H and I) high coverage (V_sample = 3.5 V, I_t = 100 pA). Regions of homogeneous-phase, striped-phase island, and striped-phase nanoribbon are indicated with red, white, and blue arrows, respectively. (J to L) STM topography images showing (J) striped-phase atomic-scale structure (V_sample = 0.1 V, I_t = 1.0 nA). Inset shows rectangular lattice with overlaid lattice vectors. (K) Striped phase with rhombohedral (indicated by white rhombus) and honeycomb (indicated by purple arrow) Moiré patterns (V_sample = 3.5 V, I_t = 100 pA). (L) Striped-phase island, demonstrating carpet-mode growth (V_sample = 3.5 V, I_t = 100 pA). Inset shows atomic continuity across the Ag(111) step (V_sample = −0.5 V, I_t = 700 pA).