1. Excitation of surface plasmons with a scanning tunneling microscope Tao Wang, Elizabeth Boer-Duchemin, Yang Zhang, Geneviève Comtet, Gérald Dujardin ISMO, ORSAY Projet ANR/PNANO « Nanosources de photons » 1

2. Surface Plasmon Polariton x z Surface plasmon polariton (SPP): EM wave confined at Metal-dielectric interface, coupled with oscillation of surface charges M D k spp > k 0 λ SPP <λ 0, Beat the diffraction limit ! 2 ω=ck 0 k SPP ω0ω0

3. Motivation Our experiment is to do local electrical excitation of surface plasmons on a gold film by STM as a nanosource of photons. Kspp k0 e- STM tip Kspp 3 laser Surface plasmon excitation: usually with light Our experiment: surface plasmon excitation with a scanning tunneling microscope

4. Experiment setup STM head Inverted optical microscope 4

5. Experiment 1: thin gold film (35nm) Experiment 2: thin gold film (35nm) with gold nanoparticles(NPs) Experiment 3: thick gold film (200nm) with holes Experiments

6. oil objective 100X, NA=1.45 W tip, 2.5V, 6nA Experiment 1: STM excited on thin gold film (35nm) Image plane image with oil objective 10 μm Image plane 6 Surface plasmon propagates on the gold film Gold films deposition in IEF CTU, Orsay

7. Experiment 1: STM excited on thin gold film (35nm) Fourier plane R=n×sin (θ)×f R Fourier plane 7 f f

8. 8 Surface plasmons emit at large angles (related to leakage radiation coupling) oil objective 100X, NA=1.45 W tip, 2.5V, 6nA R Experiment 1: STM excited on thin gold film (35nm) Fourier plane images with oil objective θspp nk 0 Coupling condition : kspp=nk 0 sin(θspp) kspp kspp›k 0, sin(θspp)=kspp/nk 0 ›1/n, θspp›critical angle

9. Experiment 1: STM excited on thin gold film (35nm) Spectra measurement

10. STM can excite propagating surface plasmon on the gold film (broad spectra band) Propagating surface plasmons emit at large angles This will be published on nanotechnology soon. Experiment 1: STM excited on thin gold film (35nm) Conclusion

11. 500nm NP1 NP2 Experiment 2: thin Au film (35nm) with Au NPs STM topography image (9μm×9μm) NP1 NP2 Collaboration with Prof. Hynd Remita (LCP, Orsay) Tip position

12. Experiment 2: thin Au film (35nm) with Au NPs Preliminary results image plane image 9μm×9μm

13. Propagating surface plasmon scattered by the Au NPs STM excite propagating surface plasmon on the gold film Experiment 2: thin Au film (35nm) with Au NPs Preliminary conclusion

14. Experiment 3: thick gold film (200nm) with nanoholes STM Topography image (6μm×6μm) Collaboration with Serge Huant (Néel, Grenoble) 3μm3μm

15. 5μm STM excited light emission image Experiment 3: thick gold film (200nm) with nanoholes Preliminary results

16. Propagating surface plasmon scattered by the nanoholes STM excite propagating surface plasmon on the gold film Experiment 3: thick gold film (200nm) with nanoholes Preliminary conclusion

17. Experiment 1: thin gold film (35nm) Experiment 2: thin gold film (35nm) with gold nanoparticles(NPs) Experiment 3: thick gold film (200nm) with holes Conclusions and future work

18. Thank you for your attention! 18