Dataset

Figure 1B: SERS spectra from BPT NPoM every 100ms at 20µW, showing no picocavities at low power. Figure 2: (A) Time-series SERS spectra of BPT for 50 µW 633 nm laser irradiation, showing examples of the nanocavity, a picocavity, and a flare in time-series. (B) Time-series SERS spectra of MBN for 50 µW irradiation. (C) Time-series SERS spectra of MPy for 10 µW irradiation. (D-F) Example SERS spectra from the nanocavity, a picocavity, and a flare. (G-I) DFT-calculated Raman spectra before the scaling by a factor of 0.97 (.csv and .out), with the corresponding molecular structures (.out). Figure 3: (A) Raw formation times and (B) lifetimes of picocavities, for the example histograms (with bin size of 20 and 30 respectively) in log scale. (C) Formation rate of picocavities at room and cryogenic temperatures, with critical intensities. (D) Formation rate of flares, with critical intensities. (E) Critical laser intensity required for picocavity and flare formation (from C,D), and saturation decay rate of slow picocavities (from F), vs molecule-metal binding energy. (F) Decay rate of picocavities in log scale, split into two classes (observed as in B): fast (<10 s for BPT, <25 s for MBN, MPy) and slow lifetimes. (G) Decay rate of flares, with fast (<2 s) and slow lifetimes. Figure 4E: Simulated energy for picocavities when molecule tip-adatom separation decreases by light vs without molecule, showing reduced barrier height. Note y values start from Row 87. Figure 5: (A) Simulated dependence of energy barrier and picocavity formation rate vs laser power in Model 2 for BPT. (B,E) DFT calculated charge induced on the tip atom (here N for MPy) when the gold adatom field is treated as an optical dipole of strength p at distance z away. (C,F,I) Induced charge q mapped vs adatom position, with z and angle θ on planes perpendicular to the aromatic ring. (D) Extracted energy barriers for different molecules from data. (G) Induced charge q from DFT tracks tip atom polarizability. (H) Molecule-metal binding energy well depth, and critical laser intensity, required for picocavity and flare formation, vs induced charge q at the molecule tip atom.

Python (https://www.python.org/); Igor Pro (https://www.wavemetrics.com/)