Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 46: Electronic Structure of Surfaces: Spectroscopy, Surface States

O 46.6: Poster

Tuesday, March 21, 2017, 18:30–20:30, P1A

Multi-electron photon-emission from a tunnel junction — •Philip Kapitza, Ebru Ekici, Kira Kolpatzeck, Rolf Möller, and Christian A. Bobisch — Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany

Inelastic tunneling processes in the tip/sample junction of a scanning tunneling microscope (STM) can excite tip induced plasmon modes (TIP), which can decay radiatively. The emitted light carries information about the underlying inelastic processes. We observe light emission between the visible and the near infrared range from the junction between a silver covered STM tip and a Ag(111) surface. The applied voltage V_Bias, limits the maximum energy E_max= eV_Bias of the tunneling electrons. Normalized Emission spectra show emission tails exceeding E_max, supposedly caused by natural linewidth broadening. A comparison with calculated tunneling probabilities for inelastic transitions results in electron-lifetimes of the excited states in the range of 30 fs to 80 fs. If the tunneling current I_T is unusual high (nA to µA), two or more electrons may interact and exchange energy and non-linear processes may be triggered [1], [2]. In this case, photons with an energy E_max < E_photon < 2E_max can be observed. For these cases, spectra of emitted light are discussed as a function of the tunneling parameters. However, the emission spectra reveal the same spectral features, indicating that the same TIP modes are excited.

[1] G. Hoffmann et al., Phys. Rev. Lett. 90, 046803-1 (2003).

[2] G. Schull et al., Phys. Rev. Lett, 102, 057401 (2009).