Extended Data Fig. 1: Characterization of Sn vacancy defects.

a, Se K-edge k2χ(k) EXAFS oscillation functions for SnSe NSs and bulk crystals. The reduced oscillation amplitudes in the 4 − 10 Å−1 range for SnSe NSs indicate structural disruptions associated with Sn vacancy defects. b, Corresponding Fourier transforms of the EXAFS spectra. c, EPR spectra of Sn1−xSe NSs and SnSe bulk crystals. d, Calculated defect concentration derived from the EPR spectra. e, Raman spectra of Sn1−xSe NSs and SnSe bulk crystals, exhibiting four characteristic peaks at 68.5, 103.1, 127.5 and 149.4 cm–1, correspongding to the Ag(1), B3g, Ag(2) and Ag(3) vibration modes of SnSe, respectively. The Sn1−xSe NSs exhibit broadened and diminished peaks compared to bulk crystals, indicating their ultrathin structure and the presence of defects. f, Calculated B3g/Ag(1) intensity ratios, demonstrating an increase in Sn vacancy defects with higher x values.