Surface plasmonpolaritons can be excited due to tunneling electrons in an STM’s tunnel junction.Such excitations may lead to localized charge density oscillationsthat can reach to optical frequencies. This way photon emission can occur between the STM tip and the surface of interest.Consequently, Scanning Tunneling Microscope (STM) may be used for not only imaging topographies of specimens at the atomic scale, but also observation of photon emission from tunneling junction may be managed [1]. Theory of photon emission from tunneling junction was explained by excitation of local surface plasmon modes in the tip-sample cavity [2, 3]. Although local electronic properties of scanned areas have prior role in the rate of photon emission, there is a significant dependency on the local topographic properties such as radius of surface clusters [4], grain variety [5] and the tip factor [6, 7, 8]. In our work, the main goal is to find out the properties of photon emission from different surfaces by measuring topography and photon maps simultaneously with an integrated optical setup to a commercial STM head, under ambient conditions.

Diagram of pSTM

(a)STM image of Au surface (b)Simultaneously taken photon map (c) Comperative analysis of linescans from topography (black line) and photon map (red line).

REFERENCES:

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[4]Persson, B. N. J. & Baratoff, A. "Theory of photon emisison in electron tunneling to metallic particles." Phys. Rev. Lett.4–7, 1992.

[5]Mckinnon, A. W., Welland, M. E., Wong, T. M. H. & Gimzewski, J. K. “Photon-emission scanning tunneling microscopy of silver films in ultrahigh vacuum: A spectroscopic method.” Phys. Rev. Lett.48, 15250–15255, 1993.

[6]Johansson, P. “Light emission from a scanning tunneling microscope: Fully retarded calculation.” Phys. Rev. Lett.58, 10823–10834, 1998.

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[8]Walmsley, D. G., Tan, T. S. & Dawson, P. "Light emission from gold and silver thin films in a scanning tunneling microscope: Role of contamination and interpretation of grain structure in photon maps."Surf. Sci.572, 497–520, 2004.