Morphology and plasmonic properties of self-organized arrays of ...

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48 CHAPTER 2. EXPERIMENTAL METHODSthe oscillation amplitude; instead, by inspecting the oscillation phase variations it can beachieved a better contrast on material surface properties, such as stiffness, viscoelasticity,and chemical composition [182–186].The AFM setup employed in this work was composed of a Multimode Scanning ProbeMicroscope (fig. 2.10(a), maximum scan size 15μm) driven by a Nanoscope IV controller,both produced by Digital Instruments-Veeco, and all the images were acquired in tappingmode; an example is shown in fig. 2.10(b).[001]a. b.Figure 2.10: Panel a: picture of a Multimode Scanning Probe Microscope. Panel b: AFMimage of a 6 nm Au film on a nanopatterned LiF(110) acquired in tapping mode.
Chapter 3Self-organized nanoparticlearrays: morphological aspectsIn this chapter we present the procedures for the fabrication of lithium fluoride nanostructuredsubstrates and for the subsequent realization of ordered 2D arrays of metallicnanoparticles.3.1 Growth and characterization of lithium fluoridesubstratesWidebandgapinsulatorshavebeenextensivelyemployedastemplatesfortheguidedovergrowthof metallic structures since a long time [105, 117–121]. Insulating surfaces providea complete electronic decoupling, thus metallic adsorbates can develop a local electronicstructure with specific functionality depending on the growth conditions. Moreover, wideband gap solids are transparent from the near-UV to the near-IR range, so they easilyallow the investigation of the optical properties of the adsorbates, are quite stable in atmosphere,do not suffer oxidation (but in some cases are hygroscopic), and are usuallynot magnetic.Ionic crystals, such as NaCl, LiF, MgO, CaF 2 , KBr, are a class of insulators composedof alternating ions of opposite sign. The ions are bound together mainly by electrostaticattractions, so the electrostatic energy strongly affects the stability of the surfaces, makingcertain crystal orientations highly favoured. This peculiarity is commonly exploited forthe patterning of surfaces at nanoscale [105, 117–121]: when the crystal is cut along anunfavourable direction and the atoms are given enough mobility, the less stable surfacescan undergo faceting in favour of the more stable orientations, spontaneously leading tothe formation of regular structures. For example, faceting into ridges or pyramids, or theformation of regular ridge-and-valley structures are common phenomena observed uponthermal annealing or homoepitaxy on NaCl(111) [105], NaCl(110) [122, 187], LiF(110)[121], CaF 2 (110) [121] or MgO(110) [106].Inthisthesis, weinvestigatedandcharacterizedthehomoepitaxialgrowthonLiF(110).LiF crystals are composed of Li + and F − ions arranged on a rocksalt cubic structure, witheach ion surrounded by 6 ions of the other species (fig. 3.1). The preferential orientationsof the crystals are the {100} surfaces, consisting of alternating ions arranged on a squarelattice (fig. 3.1(c)). {110} surfaces are instead less symmetric and less stable, the ions49
Page 1: Università degli studi di GenovaFa
Page 4 and 5: 4 CONTENTS5.2.2 Optical anisotropy
Page 6 and 7: 6 Introductionconfining the EM ener
Page 8 and 9: 8 Introduction
Page 10 and 11: 10 CHAPTER 1. THEORYEλBkFigure 1.1
Page 12 and 13: 12 CHAPTER 1. THEORYfrom which, sep
Page 14 and 15: 14 CHAPTER 1. THEORY≈ ω 0 like
Page 16 and 17: 16 CHAPTER 1. THEORYε 1 (λ) = N 2
Page 18 and 19: 18 CHAPTER 1. THEORYThe correspondi
Page 20 and 21: 20 CHAPTER 1. THEORYso the induced
Page 22 and 23: 22 CHAPTER 1. THEORYε MG −ε aε
Page 24 and 25: 24 CHAPTER 1. THEORYUV range, this
Page 26 and 27: 26 CHAPTER 1. THEORYwhich is called
Page 28 and 29: 28 CHAPTER 1. THEORYwhere Γ 0 = v
Page 30 and 31: 30 CHAPTER 1. THEORYpoints of the c
Page 32 and 33: 32 CHAPTER 1. THEORYand then monoto
Page 34 and 35: 34 CHAPTER 1. THEORYposition, has t
Page 36 and 37: 36 CHAPTER 1. THEORYfieldorequivale
Page 38 and 39: 38 CHAPTER 1. THEORY
Page 40 and 41: 40 CHAPTER 2. EXPERIMENTAL METHODSt
Page 42 and 43: 42 CHAPTER 2. EXPERIMENTAL METHODSt
Page 44 and 45: 44 CHAPTER 2. EXPERIMENTAL METHODS2
Page 46 and 47: 46 CHAPTER 2. EXPERIMENTAL METHODSs
Page 50 and 51: [001][100]50 CHAPTER 3. SELF-ORGANI
Page 52 and 53: 52 CHAPTER 3. SELF-ORGANIZED NPS AR
Page 76 and 77: 76 CHAPTER 5. MODELLING AND ANALYSI
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98 CHAPTER 6. COMPOSITE MEDIA BASED
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100 CHAPTER 6. COMPOSITE MEDIA BASE
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102 CHAPTER 6. COMPOSITE MEDIA BASE
Page 104 and 105:
104 Conclusionsparticular cases of
Page 106 and 107:
106 Acknowledgements
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108 BIBLIOGRAPHY[14] Shouheng Sun,
Page 110 and 111:
110 BIBLIOGRAPHY[44] Q A Pankhurst,
Page 112 and 113:
112 BIBLIOGRAPHY[74] Prashant K. Ja
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114 BIBLIOGRAPHY[103] Tobias Kraus,
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116 BIBLIOGRAPHY[137] F. Brouers, J
Page 118 and 119:
118 BIBLIOGRAPHY[169] Christy L. Ha
Page 120 and 121:
120 BIBLIOGRAPHY[201] G. Baldacchin
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