Optoelectromechanic effects in nanocontacts: Electric-field enhancement and mechanically driven conductance changes
Final Report Abstract
This joint effort between the Japanese and the German partners deals with nano-optoelectromechanical systems. The physical questions that were addressed include optical near field enhancement in nanogaps and atomic contacts, the interplay between optical excitation and electronic transport in different device architectures, as well as thermal effects due to plasmon propagation and decay and their correlation to mechanical deformations. At the beginning of the project conflicting results were published by different research groups regarding the field enhancement in plasmonic nanostructures, measured with different methods. One goal of the project was to clarify these contradictions by systematic comparison of the methods established in the German and the Japanese groups and by simulations taking into account realistic sample geometries. In a joint effort, taking place at Sapporo, we developed a calibration procedure for the “Konstanz” method and obtained very good agreement with the findings form the Japanese partners for various geometries. The Japanese group is interested in the how the field enhancement in optical antenna pairs as well as in arrays with separations of a few nanometers varies when the distances are changed by subnanometer distances. These variations are difficult to realize by lithography and only discrete steps in the gap sizes are possible. Therefore special emphasis was devoted to tunable systems with the help of silicon nanomembranes. The membranes can be deformed either locally by using needles from the rear side or by pressurizing, thereby tuning the distance between the nanostructures continuously. Jointly with the Japanese partners we worked out the nanopatterning of metal structures using electron beam lithography on these membranes and installed the tuning setup developed at Konstanz at Sapporo. As we learned during the course of the project, both techniques work well for individual nanocontacts and nanogaps. However, when structuring larger arrays the uniformity is less good as on solid substrates, hampering the observation of the impact of the continuous geometrical change. At Konstanz, we intensively studied the influence of illumination onto the electronic transport in atomic-size contacts. The goal was to separate thermal effects due to absorption from electronic effects such as photo-assisted transport and hot-electron effects and to elucidate the role of plasmons for the conductance change. By making use of propagating surface plasmons, we separated the position of the irradiation from the contact. We simultaneously measured the plasmon transport by recording the out-coupled light at gratings and at the contact and the conductance of atomic-size contacts as a function of the polarization. A detailed analysis reveals that the thermal expansion due to the decaying plasmons is not negligible. We tested different metals and substrate materials to change the relative size of the various contributions to the total conductance change. These studies are ongoing. In the future, time-resolved measurements are planned. We also developed a scheme to use optical and mechanical control of the conductance of atomic site structures. These studies revealed that on silicon membranes the thermal expansion due to absorption of light dominates the observed conductance changes, when irradiating at the constriction. Further studies using optimized materials combinations and gratings are underway. Also the collaboration with the Japanese partners is ongoing by exchange of researchers and students performing the Thesis projects in the partner lab.
Publications
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Optical transmission and laser structuring of silicon membranes, Optics Express 17, 15308 (2009)
S. Juodkazis, Y. Nishi, H. Misawa, V. Mizeikis, O. Schecker, R. Waitz, P. Leiderer, E. Scheer
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Optical temperature measurements on thin freestanding silicon membranes, Rev. Sci. Instrum. 81, 114903 (2010)
M. Schmotz, P. Bookjans, E. Scheer, P. Leiderer
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A thermal diode using phonon rectification, New J. of Physics 13, 113027 (2011)
M. Schmotz, J. Maier, E. Scheer and P. Leiderer
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Characterization and applications of plasmon fields in metal nanostructures, invited, SPIE Proc. 8204, 820404 (2011)
A. Kolloch, D. Benner, M. Bädicker, R. Waitz, T. Geldhauser, J. Boneberg, P. Leiderer, E. Scheer
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Visualization of Near-Field Enhancements of Gold Triangles by Nonlinear Photopolymerization, Plasmonics 6, 207 (2011)
T. Geldhauser, S. Ikegaya, A. Kolloch, N. Murazawa, K. Ueno, J. Boneberg, P. Leiderer, E. Scheer, H. Misawa
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Quantitative measurement of the near-field enhancement of nanostructures by two-photon polymerization, Langmuir 28, 9041 (2012)
T. Geldhauser, A. Kolloch, N. Murazawa, K. Ueno, J. Boneberg, P. Leiderer, E. Scheer, H. Misawa
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Mapping of plasmonic resonances in nano-triangles, Beilstein J. Nano. 4, 588 (2013)
S. Dickreuter, J. Gleixner, A. Kolloch, J. Boneberg, E. Scheer, P. Leiderer
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Transmission of Surface Plasmon Polaritons through Atomic-size Constrictions, New J. Phys. 15, 113014 (2013)
D. Benner, J. Boneberg, P. Nürnberger, G. Ghafoori, P. Leiderer, E. Scheer
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Lateral and Temporal Dependence of the Transport through an Atomic Gold Contact under Light Irradiation: Signature of Propagating Surface Plasmon Polaritons, Nano Letters 14, 5218 (2014)
D. Benner, J. Boneberg, P. Nürnberger, R. Waitz, P. Leiderer, E. Scheer
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Time-resolved optical measurement of thermal transport by surface plasmon polaritons in thin metal stripes, Appl. Phys. Lett., 105, 191119 (2014)
A. Ganser, D. Benner, R. Waitz, J. Boneberg, E. Scheer, P. Leiderer
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Tuning the transmission of surface plasmon polaritons across nano and micro gaps in gold stripes, Optics Express 24, 17313 (2016)
G. Ghafoori, J. Boneberg, P. Leiderer, E. Scheer
