Extended Data Fig. 9: Characterization of lithium-intercalated black phosphorus.
a, b, Example Raman spectra for Li-BP, recorded with the incident laser polarization perpendicular (a) or parallel (b) to the vertical features that are visible in the bottom part of c. The top two spectra of a, b show the results obtained in argon; the bottom two spectra were obtained from the same region in the sample after 30 days in air. These spectra were fitted with a sum (red curve) of Lorentzian functions for black phosphorus (blue curves) and intercalation (green curves) Raman modes. See Methods. c, Top, optical micrograph of an Li-BP crystal (scale bar, 200 µm); bottom, a magnified image (scale bar, 18 µm). The bottom image also shows the area (red box) over which the Raman mapping data in f were taken from. d, Histograms showing the Li/P Ag2 peak position in argon (values taken from 396 individual spectra) and after 30 days in air (taken from 324 spectra). e, Histograms showing the Ag1/Ag2 peak intensity ratio for measurements performed with the incident laser polarization parallel (taken from 180 spectra) or perpendicular (taken from 396 spectra) to the vertical stripes in c. f, Map showing the position of the Ag2 peak for data taken over the red box in c. Scale bar, 5 µm. g, TEM image showing in-plane splitting of PNRs from a larger fragment. Scale bar, 500 nm. h, HS-AFM image (top; scale bar, 100 nm) and associated linescan (bottom) of the surface of an Li-BP crystal, showing a ribbon (line profile 2, black) liberated on the surface and the trench left behind (line profile 1, red).
