Inelastic Spectroscopy and Microscopy

Schematic of an STM-LE experiment

STM Induced Light Emission (STM-LE)

In STM induced light emission (STM LE) we detect photons which may be emitted during the STM experiments. The corresponding photon spectra include information about inelastic processes within the tunnling junction. For detection, we use on the one hand a photoavalanche diode to collect the total emission intensity as a function of the tunneling parameters. On the other hand, a spectrograph equippped with a liquid nitrogen cooled CCD camera is used to analyse the spectral features of the emitted light. Thereby, we may perform point spectroscopy but also photon mapping to gain access to inelastic exctitation maps with atomic resolution.

SNM data for the tunneling current induced rotation of individual CuPc molecules

Scanning Noise Microscopy (SNM)

The noise in the tunneling current signal may also carry information about inelastic tunneling processes. We developed scanning noise microscopy (SNM), which allows us to measure different parameters of the tunneling current noise simultaneously to the STM experiment. Thereby we analyse the rate of fluctuations, the amplitude of the fuctuatons and the residual time in one of the states as a function of the tunneling parameters. This allows for a  Spectroscopic analyses as well as mapping of the noise parameters iwth atomic scale resolution. In particular, lateral resolved exitation maps may unravel the probability of inelastic processes as a function of their local environment.