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

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58 CHAPTER 3. SELF-ORGANIZED NPS ARRAYS: MORPH. ASPECTS[001][001]a. b.Figure 3.9: 2-dimensional autocorrelations of the AFM images in fig. 3.8(b) and (c). Thesuperimposed grids are guide to the eye for the positions of the maxima of the correlation.directions; the typical spacing along the [1¯10] direction matches the ripples periodicity,while theseparations in the[001] direction areonthesamescale butmoreirregular. Thesestructures indicate that the NP arrays have a good translational symmetry not only inthe direction across the ripples, as imposed by the regular spacing of the grooves, butalso along the ripples, which is unexpectedly triggered by the annealing. The extensionof the rectangular NP meshes depends on the dispersion of the particles size; it can bequite large in case of monodispersed samples like in fig. 3.8(a,b), where the majority ofthe visible particles are orderly arranged, while for samples like in fig. 3.8(d) almost nointer-ridge correlation is found.Lastly, for less than ≈ 3 nm of deposited gold a different dewetting mode occurs. Dueto the low amount of gold, the particles cannot grow as wide as the ripples, and thereforethey form multiple chains inside each grooves, similar to the situation observed before theannealing (fig. 3.7(b,d)). We report an example in fig. 3.10; the sample has a periodicityΛ ≈ 30 nm and ≈ 2.7 nm of gold were deposited. We used dashed lines to delimit thegrooves in the figure, so that double or triple chains of particles can be distinguished.Furthermore, looking at the 2D autocorrelation plot in panel (b) we can identify again aweak rectangular pattern from the NP array, indicating that even in this case the thermaldewetting favoured a partial alignment of the particles.[001]Figure3.10: Panela: AFMimageofananopatternedLiF(110)sampleafterthedepositionof t Au = 2.7 nm Au at T ≈ 100 ◦ C and annealing at T = 400 ◦ C; the vertical dashedlines emphasizes the periodicity of the ripples. Panel b: 2D autocorrelation of the imagein panel a.
3.2. 2D ARRAYS OF GOLD NANOPARTICLES 59Summarizing, we have observed that it is possible to fabricate regular arrays of noblemetalNPs on insulating substrates by means of self-organization approaches, in whichimportant morphological parameters, like the mean NP size, shape and mutual spacing,can be controlled by means of various fabrication parameters. This flexibility in NP arrayfabrication will be exploited to correspondingly tune their plasmonic response, as detailedin the following chapter.
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Università degli studi di GenovaFa
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4 CONTENTS5.2.2 Optical anisotropy
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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 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
Page 98 and 99: 98 CHAPTER 6. COMPOSITE MEDIA BASED
Page 100 and 101: 100 CHAPTER 6. COMPOSITE MEDIA BASE
Page 102 and 103: 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,
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110 BIBLIOGRAPHY[44] Q A Pankhurst,
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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
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118 BIBLIOGRAPHY[169] Christy L. Ha
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120 BIBLIOGRAPHY[201] G. Baldacchin
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