Time-autocorrelation in scanning-tunneling-microscope-induced photon emission from metallic surface

We analyze the statistical properties of the photons emitted at the junction of a scanning tunneling microscope by time-autocorrelated two-photon counting measurements, with time resolutions down to the nanosecond scale. In the case of a gold surface at air, we show that the tip-induced luminescence exhibits a clear bunching phenomenon at a 10 ns time scale. Moreover, this two-photon time correlation appears to be strongly bias dependent, with an onset of the bunching behavior near 2.5 V. (C) 2000 American Institute of Physics. [S0003-6951(00)00449-6].