| AVS 65th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology Division | Tuesday Sessions |
| Session NS+AM+MI+MN+SS+TR-TuA |
| Session: | SPM – Probing and Manipulating Nanoscale Structures |
| Presenter: | Songbin Cui, Pohang University of Science and Technology, Republic of Korea |
| Authors: | S. Cui, Pohang University of Science and Technology, Republic of Korea U. Ham, Institute for Basic Science (IBS), Republic of Korea T.-H. Kim, Pohang University of Science and Technology, Republic of Korea |
| Correspondent: | Click to Email |
Photon signal can be enhanced significantly by modifying the plasmonic nanocavity. This enhancement becomes an important issue in super-resolution microscopy and high resolution spectroscopy, such as scanning tunneling microscopy (STM) electroluminescence [1], surface enhanced Raman spectroscopy, tip enhanced Raman spectroscopy [2], and so on. Low temperature STMs can allow us to achieve less than 1nm tip-sample gap stably. This gap-mode plasmonic nanocavity between an STM tip and surface realizes sub-molecular photon spectroscopy [1]. A few works demonstrated that light emission signal can be effectively enhanced by certain resonant plasmonic spectral peaks, which can be modified by tip indentation [2] and showed theoretically that the larger tip aperture causes a blue shift and the shaper apex curvature results in higher intensity in a photon spectrum [3]. However, the tip shape dependence of the plasmonic nanocavity remains unclear. In this work, we experimentally present the role of tip shape in surface plasmonic light emission. We have used Ag tips and a Ag(100) substrate, and photon signals have been measured from both side of the STM tip simultaneously. We dipped STM tips into the substrate with controlling the dipping depth and the lifting speed in order to change the tip shape, and then, the tip shape subsequently was checked through STM profiles. We found that changing small parts of tip apex (<3nm tip direction) can differ the photon spectrum significantly. Furthermore, the plasmonic photon emission from different direction from a STM tip could be quite different due to tip shape asymmetry. This finding can help us to tune the plasmonic photon emission spectra more efficiently.
[1] R. Zhang et al., Nature 498, 82–86 (2013).
[2] Z. C. Dong et al., Nature Photonics 4, 50–54 (2010).
[3] J. Aizpurua et al., Physical Review B 62, 2065-2073 (2000).