Fig. 1: Experimental setup and electron-beam excitation pathways.
a Schematic of the cathodoluminescence (CL) detection setup, utilizing a spectrometer and Hanbury Brown--Twiss (HBT) interferometer. b Close-up illustration comparing indirect excitation (via secondary electrons (SE) and backscattered electrons (BSE) generated in substrate) and direct excitation of SiV− color centers in diamond. c Inelastic collisions between the incoming primary electrons and substrate atoms generate numerous low-energy SEs. d An elastic collision deflects a primary electron back toward the surface with much of its initial energy retained, creating a high-energy BSE that can escape the material. e, f CL spectra and photon-correlation measurements for direct (green) and indirect (blue) excitation at the same current, obtained from positions indicated in SE map in (g) (scale bar is 5 μm). h Corresponding to (g) log-scaled spatial map of SiV− CL, where the dark-red core marks the intensity from directly excited centers in the diamond, and the concentric fall-off captures the radially decaying indirect excitation of SiV− CL on a gold substrate (pixel size 500 × 500 nm2, exposure time 0.2 s).
