Figure 1.
A scanning tunneling microscope combined with a Hanbury Brown and Twiss interferometer. Light radiating from a junction formed between a Au tip and multilayer C60-Ag(111) substrate travels along optical paths (1, 2) containing (L)enses and (V)iewports to a pair of single-photon avalanche detectors (SPADs). The number of photon coincidence events as a function of time delay t between pulses from the SPADs, g(2)(t), is measured with a time-correlated single-photon counter (TCSPC). The voltage bias (U) is applied to the substrate. The tunnel current (I) is measured with a picoammeter (A). A third optical path to an optical spectrometer is not shown.