Electronic excitations in thin metallic films

Transcription

1 NanoSpain Conference00, Malaga(Spain) Electronic excitations in thin metallic films,,,, 3,3, 4 V. Despoja, J. P. Echeverry, E. V. Chulkov, V. M. Silkin Donostia International Physics Center (DIPC), P. Manuel Lardizabal 4, 008 San Sebastian, Spain Centro de Fisica de Materiales CFM-MPC, Centro Mixto CSIC-UPV/EHU, 008 San Sebastian, Spain 3 Depto. de Fisica de Materiales, Facultad de uimica, Universidad del Pais Vasco, Apto. 07, 0080 San Sebastian, Spain 4 Ikerbasque, Basque Foundation for Science, 480 Bilbao, Spain

2 Contents :. Introduction and motivation. Mathematical formulation and modeling of the system 3. Excitation spectra inside ultra thin silver films;,, 3ML-Ag() films 4. Excitation spectra inside thicker silver films and transition to semiinfinite metals; 7ML, 3ML-Ag() films 5. Conclusion

3 . Introduction and motivation Why is proper knowledge of the electronic excitations at metallic SSP surface important?.plasmonic circuits-guided surface plasmons (polariton) could be subject to significant Landau damping. Berni P. et al, J. Appl. Phys (005).Plasmonic devices-thin silver film covered from both sides by thin polimer films with molecular chromophores. ENERGY TRANSFER ACROSS A METAL FILM MEDIATED BY SURFACE PLASMON POLARITONS light Ag-film c Surface plasmon (polariton) Andrew P. and Barnes W. L., Science (004) Exciteddonor molecule 0nm Ag-film Ground stateacceptor molecule 3.Biosensing Metal-enhanced fluorescence: Surface plasmon can radiate a Fluorophore s structured emission. Yongxia Zhang, et al, Appl. Phys. Lett. 90,05307 (007) uenching!! Ag-film E v F Interband e-h transitions Acoustic surface plasmon Intraband e-h transitions 4.Light-emitting structures semiconductor W coated by thin silver films increse spontaneous emission in W. Efficient energy transfer from electron-hole pair recombination (in W) to a surface plasmon (in silver film). Energy is converted into light by using corrugated metal-semiconductor interface. A. Neogi, et al, Phys. Rev. B 66, (00) K. Okamoto, et al, Appl. Phys. Lett (005) Ag-film Semiconductor W

4 . Mathematical formulation and modeling of the system 0. 6nm Enegy absorption! Sudden created point charge near Ag() surface, V.M. Silkin, Poster 90 z 0 z V ext e zz0 e cos( t) Ag() P loss ind ImW (,, z 0, z ), 0 W ind ( 0 z, 0, z0, z0) e g(, ) Surface response function g(, ) dz z z R,, z z dze, Img(, ) Intensity of the real excitations in the system! Response function-rpa R R0 vr 0

5 Free electron response function Band structure and wave function-d model potential E.V. Chulkov, V. M. Silkin and P.M. Echenique, Surf.Sci. 437 (999) Parameters of the potential are set up to fit experimental (first principle) datas for surface state, first image state and postion and width of band gap at point Band structure and wave functions- solutions of D Schrodinger equation: d m* dz V MP z z E z n n n E n, K E n K m*

6 3. Excitation spectra inside ultra thin silver films ML(0.nm)- Ag() film E F ML-one quasi D electron gas D eff (, ) V R D (, ) E V v dz dz Im (, ) 0 eff e 0 ( z z ) z e z Re (, ) 0 eff D k F m*

7 ML(0.4nm)- Ag() film ML- Ag() ML-two quasi D electron gases E E F F F v v E Approximationes: a) Longwavelenght limit 0 b) There are no transitions between bands and E E ML-Two component quasi D electron plasma-egzistence of fast and slow electron plasmas allow forming of Acoustic Surface Plasmon (ASP). D eff (, ) v ASP v S R D. Pines, Can J. Phys. 34, 379 (956) D (, ) R F F vs v v 3 v D F, (, ), E m * F E, 3ML, 4ML,... Multiplication of acoustic surface plasmon branches F F F v v v v v... i ASP v i S S S

8 ML(0.4nm)- Ag() film Ag() v F v F Ag(jellium)

9 3ML(0.6nm)- Ag() film Ag() v F v F v F 3 Ag(jellium) Interband Plasmon!?

10 7ML(.4nm)- Ag() film Ag() ASP Interband Plasmon! Ag(jellium)

11 4. Excitation spectra inside thick silver films and transition to spectra in semiinfinite metals 3(6nm)ML- Ag() film 3D-electron plasma D-electron plasma J. M. Pitarke, V. U. Nazarov, V. M. Silkin, E. V. Chulkov, E. Zaremba, and P. M. Echenique Phys. Rev. B 70, (004) V. M. Silkin,J.M. Pitarke, E. V. Chulkov and P. M. Echenique Phys. Rev. B 7, 5435 (005) D eff W (, ) W 3D (, ) R D SS (, ) 3D (, ) dzdz SS SS z 3D z W (,, z, z ) Dispersion relation equation D (, ) 0 eff ASP vss F Without 3D electron plasma W (, ) v e 3 D One quasi D electron gas D

12 3(6nm)ML- Ag() film Ag() L. Marušić, V. Despoja and M. Šunjić, J. Phys.: Condens. Matter 8 (006) 45 Ag() =0.0 a.u. Al(4nm-jellium)

13 5. Conclusion ARPES measurements of quantum size effects I. Matsuda et al, J. Surf. Sci. Nanotech. Vol. (004) Ultra thin metallic films quantum size effect multicomponent D plasma multiplication of ASP branches..thin metallic slabs interband plasmon. It would be nice to investigate how it couples to light. 3.Semiinfinite noble metals () surfaces. Slow D plasma (surface state band) + fast 3D plasma (bulk state bands) =Acoustic Surface Plasmon c

14 Thank you for your attention!