Optical resonances of sphere-on-plane geometries [Elektronische Ressource] / Adriana Rueda Gomez

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Sujets

• Physik

Informations

• Publié par: johannes_gutenberg-universitat_mainz
• Publié le: 01 janvier 2008
• Nombre de lectures: 126
• Poids de l'ouvrage: 10 Mo

Extrait

Optical resonances of sphere-on-plane geometries
Dissertation zur Erlangung des Grades
„Doktor der Naturwissenschaften“
am Fachbereich Physik, Mathematik und Informatik
der Johannes Gutenberg-Universität
in Mainz

Adriana Rueda Gomez
geboren in Bucaramanga, Kolumbien

Mainz, Juli 2008














1. Gutachter: [Removed]
2. Gutachter: [Removed]
Tag der mündlichen Prüfung: 27.10.2008

Dieser Arbeit wurde in der Zeit von Juli 2005 bis Juli 2008 unter der Betreuung von
[Removed] und [Removed] am Max-Planck-Institut für Polymerforschung in Mainz
angefertigt.
Contents

Contents
1 Introduction ........................................................................................................................ 3
2 Basic concepts .................................................................................................................... 7
2.1 Metal optics................................................................................................................ 7
2.2 Optical resonances of metallic nanostructures ......................................................... 13
2.3 Surface enhanced luminescence............................................................................... 27
2.4 Experimental techniques .......................................................................................... 30
3 Characterization of gold films by surface plasmon spectroscopy: Large errors and small
consequences............................................................................................................................ 34
3.1 Experimental ............................................................................................................ 35
3.2 Results ...................................................................................................................... 36
3.3 Conclusions .............................................................................................................. 45
3.4 Acknowledgements .................................................................................................. 46
4 Localized plasmons seen by propagating surface plasmons: Unique determination of
their dielectric response............................................................................................................ 47
4.1 Introduction .............................................................................................................. 47
4.2 Experimental ............................................................................................................ 48
4.3 Experimental results and discussion ........................................................................ 51
4.4 Applicability of the analysis in terms of α/A........................................................... 66
4.5 Conclusions .............................................................................................................. 71
4.6 Acknowledgements .................................................................................................. 72
5 Optical resonances of gold nanoparticles on a gold surface: Quantitative determination of
the geometry............................................................................................................................. 73
5.1 Introduction .............................................................................................................. 73
5.2 Experimental ............................................................................................................ 75
5.3 Experiment: Variation of the sphere-on-plane resonator parameters....................... 78
5.4 Theory ...................................................................................................................... 84
i Contents
5.5 Quantitative analysis: determining a gap thickness interval .................................... 88
5.6 Resolving the ambiguity in ε /d ........................................................................... 91 sp sp
5.7 Conclusions .............................................................................................................. 92
5.8 Acknowledgements .................................................................................................. 93
6 Surface-enhanced fluorescence from the ‘hot spots’ of sphere-on-plane systems........... 94
6.1 Introduction .............................................................................................................. 94
6.2 Experimental ............................................................................................................ 96
6.3 Fluorescence of the spacer molecules ...................................................................... 99
6.4 Sample characterization ......................................................................................... 101
6.5 Influence of the surface roughness......................................................................... 104
6.6 Enhancement .......................................................................................................... 110
6.7 Conclusions ............................................................................................................ 114
6.8 Acknowledgements ................................................................................................ 115
7 Conclusions .................................................................................................................... 116
Appendix A ............................................................................................................................ 118
A.1 Synthesis of PDIG ...................................................................................................... 118 2
A.2 Summary of samples ................................................................................................... 120
A.3 Spacer layer investigations.......................................................................................... 123
List of abbreviations............................................................................................................... 129
References .............................................................................................................................. 131
Summary ................................................................................................................................ 143
Zusammenfassung.................................................................................................................. 145
Acknowledgements ................................................................................................................ 147



ii Chapter 1: Introduction

1 Introduction
The first indications of a special kind of interaction in systems consisting of a metal sphere
with dimensions in the range of the wavelength of light placed at nanometer distances to a
metal plane were found in tunnel junction experiments (Lambe and McCarthy 1976; Hansma
and Broida 1978). Tunnel junctions were seen to emit light when a voltage was applied across
the junction. This effect was first interpreted to be due to the excitation of surface plasmons
by the tunneling electrons. The surface plasmons decayed by sending out light. Surface
plasmons on perfectly smooth surfaces do not radiate. Nevertheless, it was thought that in
these experiments the surface roughness of the junctions made the mechanism possible. With
the invention of scanning near field optical microscopes, investigations started to study the
role of the tip in the rate of light emission from the tunnel junction created between the tip and
the surface studied (Johansson, Monreal et al. 1990). It was found that the tip itself and not
only the surface were important. The tip was recognized to play a similar role as the surface
roughness by breaking the translational invariance along the surface. The light emission and
frequency were dependent on parameters such as the tip curvature and distance of the tip to
the surface. The effect was re-interpreted as to be due to an optical resonance termed
“localized interface plasmon” built up between the tip and the surface.
Independently in molecular spectroscopy, large enhancements of the Raman cross section
were encountered in experiments combining electrochemistry and Raman spectroscopy of the
molecule pyridine. Fleischmann et al. (Fleischmann, Hendra et al. 1974) had the idea to
increase the amount of adsorbate on the surface by increasing the surface area. For this, they
made the silver electrode very rough. They observed a huge increase in Raman signal, a
process which is commonly very inefficient. Soon it was found out (Albrecht and Creighton
1977; Jeanmaire and van Duyne 1977) that the effect could not be explained by the increase
of scatterers on the surface. Other mechanisms were proposed in which the Raman cross
section of the individual molecules was enhanced in the adsorbate state (Jeanmaire and van
Duyne 1977) and in which enhancement mechanisms due to optical resonances played a role
(Philpott 1975). It was not clear whether the effect had an electromagnetic or chemical origin.
The mechanisms behind this process, called Surface Enhanced Raman Scattering (SERS)
b