Title Page
Abstract
Contents
Chapter 1. Introduction 22
1.1. Structural Coloration 24
1.2. Surface-enhanced Raman Spectroscopy 28
1.3. Outline of Thesis 31
Chapter 2. Theoretical Background 32
2.1. Fabry-Perot Optical Resonator 32
2.2. Bruggeman's Effective Medium Theory 35
2.3. Raman Spectroscopy 35
Chapter 3. Full-colored Structural Coloration with Thin-film Etalon Composed by Gold-nanoparticle Effective Medium 38
3.1. Introduction 38
3.2. Basic Concept 39
3.3. Experiments 42
3.3.1. Fabrication of Au-PBVE-Au etalon 42
3.3.2. Reflectance spectrum measurement 44
3.4. Results and Discussions 46
3.4.1. Nanomorphology of Top Au 46
3.4.2. Colormap simulation of MDM etalon 49
3.4.3. Optimum Top Au Thickness for Wide Color Coverage 53
3.4.4. Tailoring Dielectric Layer via Reactive Ion Etching 55
3.4.5. Multiple Colors for Environmental Function Mimicry 59
3.5. Summary 64
Chapter 4. Naked-Eye Observation of Water-forming Reaction on Palladium Etalon: Transduction of gas-matter interaction into light-matter interaction via Palladium 65
4.1. Introduction 65
4.2. Basic Concept 66
4.3. Experiments 70
4.3.1. Fabrication of Pd-based FP Etalon Substrates 70
4.3.2. FLIC Pattern Analysis and Thickness Simulation 70
4.3.3. Gas Control and Optical Analysis 73
4.3.4. DFT Calculation 75
4.4. Results and Discussions 76
4.4.1. Interfacial Confinement of Water-forming Reaction at FP Cavity for Dynamic Plasmonic Coloration 76
4.4.2. Water Bubble Formation at the Polymer/Pd Interface 79
4.4.3. Optical Foggy Effect by Water Bubbles Induced Light Diffusion 86
4.4.4. Multichromatic Change by the Water-film Formation and Following Whiteout Effect 93
4.4.5. Scalable and Transparent Display for Gas Detector via Water-forming Reaction 98
4.5. Summary 106
Chapter 5. Fabry-Perot Cavity Control for Tunable Raman Scattering 108
5.1. Introduction 108
5.2. Basic Concept 109
5.3. Experiments 112
5.3.1. Fabrication of an FP Etalon Substrate for Dynamic SERS Signal Tuning 112
5.3.2. SERS Measurements 112
5.3.3. Numerical Simulations 113
5.4. Results and Discussions 114
5.4.1. Underlying Principles of Tunable SERS Effect on the FP Etalon 114
5.4.2. Maximization of Near-field Raman Enhancement via Au Nanoparticular Assembly 118
5.4.3. Modulation of Far-field Raman Enhancement Effect via Dielectric Tuning 126
5.4.4. Dynamic SERS Signal Tuning via Dielectric Modulation 134
5.4.5. Raman message encryption via FP etalon-based dynamic SERS substrate 141
5.5. Summary 147
Chapter 6. Concluding Remarks 149
Acronyms 153
Bibliography 154
Publications 166
Abstract (In Korean) 169
Figure 1.1. Examples of structural color generation by photonic crystals (a; reproduced from [24]), polymer opals (b; reproduced from [29]), and FP... 27
Figure 1.2. Conceptual outline of the main elements of SERS (reproduced from [37]) 30
Figure 2.1. Schematic description of FP optical resonator, reproduced from [46]. 34
Figure 2.2. Schematic description of Raman scattering, reproduced from [48]. 37
Figure 3.1. Schematic illustration of proposed MDM stack varying configuration of composing materials. 41
Figure 3.2. (a-g) Schematic illustration of etching and surface treatment processes of discus fish sample fabrication. Steps (a-c) and (g) are etching... 43
Figure 3.3. Schematic diagram of reflectance spectrum measurement. At the lower-left corner, the reflection probe is schematically illustrated as having one... 45
Figure 3.4. (a) MDM structure is composed of Si substrate, 100 nm thick reflective Au film, PBVE and Au/air mixture layer with various thickness in... 47
Figure 3.5. Surface hydrophobicity of PBVE. (a-d) Microscopic images of 10uL of DI water droplets on the PBVE layer after each surface treatment... 48
Figure 3.6. Simulated reflective color maps of the MDM etalon with (a) 110, (b) 135, and (c) 165 nm tPBVE, depending on various Au/air mixed layer...[이미지참조] 51
Figure 3.7. (a-c) Simulated reflectance spectra and extracted colors. (d-f) Experimentally measured reflectance spectra of the fabricated etalon samples... 52
Figure 3.8. (a-d) Simulation results of colors that can be obtained by changing the structural condition of proposed etalon. In each figure, the structural condition is... 54
Figure 3.9. (a) Schematic cross section of a MDM etalon before and after RIE. (b) Cross-sectional SEM images of the etalon samples with different fPBVE (1.00,...[이미지참조] 57
Figure 3.10. (a) Simulated color map of the proposed structure depending on neff·tPBVE where fAu= 0.80 and tAu= 35nm. Indicated marks represent the color...[이미지참조] 58
Figure 3.11. (a) Schematic description of the sample fabrication process. (b) Photograph of the resulting sample. (c-f) SEM images showing top surfaces of... 61
Figure 3.12. (a) Schematic cross-sectional layer information of the discuss fish demonstration sample with measured fAu, tPBVE, and fPBVE followed by...[이미지참조] 62
Figure 3.13. (a-c) Schematic description and (d-f) photographs of a BEE in various medium. Water does not infiltrate into the hollow insulator area,... 63
Figure 4.1. Overall mechanism and phenomena of water-forming reaction at FP etalon. Layer description of FP etalon and H₂/O₂ adsorption on the Pd... 68
Figure 4.2. Conceptual illustrations of atomical gas adsorption and sequential water-forming reactions inducing water bubble formation over the O₂-... 69
Figure 4.3. Expected interference patterns and FL intensity depending on the water bubble height. Simulated normalized FL intensity for hwater from 110 nm...[이미지참조] 72
Figure 4.4. Experimental Set-up. Schematic diagram of the gas exposure chamber with reflectance spectrum measurement. Each gas flow rate of N₂, O₂,... 74
Figure 4.5. Energy profiles for dissociative adsorption of H₂/O₂ and H₂O formation/desorption on the Pd(111) surface initially exposed to O₂ (Black) and... 78
Figure 4.6. Schematic illustrations for understanding the underlying mechanism of water bubble formation on Pd surfaces after H₂/O₂ adsorption... 82
Figure 4.7. Effect of gas permeability of the insulator on water-forming reaction and following spectral response. Photographs and measured... 83
Figure 4.8. Top-view microscopic images and corresponding side-view illustrations of PBVE-coated Pd surface under H₂ gas exposure at atmospheric... 84
Figure 4.9. Concepts and working principles of FLIC observation for micron water bubble formation at PBVE/Pd interface. d) FL intensity of micrograph... 85
Figure 4.10. Schematic illustrations of FP etalon prior to (left) and post to (right) the water bubble formation with resultant optical effect. b, c) SEM images of... 89
Figure 4.11. Photographs of FP etalon on a 4-inch wafer under 10% H₂ showing color reversibility at atmospheric condition. Scale bar in, 2 cm. 90
Figure 4.12. (a) Measured reflection spectra as a function of H₂ concentrations (0-10%) at the red-dashed area of Fig. 4.10. b) Sampled reflection spectra (each... 91
Figure 4.13. Repeatability test of FP etalon undergoing H₂ exposure for 28 times over 2.5 h. 92
Figure 4.14. Schematic illustrations describing water-film formation on β-phase PdH surface. 95
Figure 4.15. Time-lapse photographs of the FP etalon under 10% H₂ followed by 20% O₂ exposure. Scale bar, 2 cm. 96
Figure 4.16. (a) Measured reflection spectra as a function of O₂ concentrations (0-20%) at β-phase PdH surface (red-dashed area of Fig. 4.15). (b) Sampled... 97
Figure 4.17. Schematic layer description (a) and photograph (b) of 12 fabricated f-etalon samples on glass substrate. Scale bar, 1 cm. 101
Figure 4.18. The f-etalons prepared with different top metals with various filling fraction. Top view SEM images and photographs of f-etalons of which... 102
Figure 4.19. Photographs of the sample with Ag top film displaying color variation in response to different gas composition. Scale bar, 1 cm. 103
Figure 4.20. Angle-dependent color variation and foggy effect under H₂ exposure. Scale bar, 1 cm. 104
Figure 4.21. Scheme of f-etalon on glass applied for H₂ leakage warning window (a) and its demonstration in a miniaturized H₂ storage facility (b). Scale... 105
Figure 5.1. Conceptual illustrations of tunable Raman signals via the structural modulation of FP etalon. 111
Figure 5.2. Conceptual illustrations of SERS intensities from uniform distribution of randomly dispersed Au nanoparticles and manipulation of... 116
Figure 5.3. Top- (a) and side-view (b) SEM images of FP etalon for tunable Raman substrate. 117
Figure 5.4. Effect of top Au nanoarchitecture on SERS intensity. (a) Schematic description of top Au nanogeometry on the PBVE surface as a function of... 121
Figure 5.5. Computer simulation showing amplified electric-field distribution on three representative Au structures with tAu values of 10, 30, and 70 nm. Each...[이미지참조] 122
Figure 5.6. (a) Raman spectra of thiophenol measured from the substrates in Fig. 5.5b under 785-nm laser. (b) Plot of Raman intensity at a Raman shift of... 123
Figure 5.7. Limit of detection for 40-nm-thick nanostructured top Au on a PBVE surface. (a) Measured Raman spectra of the BPE molecules at different... 124
Figure 5.8. Optical transparency of PBVE and Raman spectra collected from the front and back sides. (a) Schematic illustration of Raman measurement on... 125
Figure 5.9. Examples of measurement fitting to estimate tPBVE. (a-c) Experimentally measured reflectance (blue) and simulated reflectance (red) on...[이미지참조] 129
Figure 5.10. (a) Measured reflective spectra for different dielectric layer thicknesses with varying tPBVE. (b) Simulated SERS EF in FP cavity (cavity EF)...[이미지참조] 130
Figure 5.11. (a-c) Simulated reflectances at tPBVE= 205, 250, and 290 nm to compare the excitation (λex) and scattering wavelengths (λsc). The cavity EF is...[이미지참조] 131
Figure 5.12. (a) Reflectance spectra with etching durations ranging from 0 to 45 s (tPBVE = 240 nm). (b) SERS performance of the dielectric layer tailored...[이미지참조] 132
Figure 5.13. Detection limit of MDM SERS device. SERS spectra of BPE molecules on the MDM structure. The samples were prepared with tPBVE of 240...[이미지참조] 133
Figure 5.14. Measured reflectance spectra (a, c) and SERS spectra (b, d) of thiophenol absorbed on nanostructured Au layer under media of n = 1.0 (Air)... 136
Figure 5.15. (a) Simulated cavity EF with ethanol immersion. (b) Comparison of SERS intensity at 1573 cm⁻¹ (I₁₅₇₃) with PBVE volume fraction (fPBVE = 1.0...[이미지참조] 137
Figure 5.16. Measured SERS intensity and simulated cavity EF at 1573 cm⁻¹ under ethanol (EtOH, n = 1.33). 138
Figure 5.17. Uniformity of MDM SERS etalon. (a, b) The Raman mapping images were obtained with a step size of 20 μm. The relative standard... 139
Figure 5.18. Raman intensity modulation via liquid infiltration. (a), Measured reflectance spectra from MDM etalon consisting of tBottom_Au = 120 nm, ttop_Au =...[이미지참조] 140
Figure 5.19. Conceptual illustration (a) and photograph (b) of the prepared FP sample for message encryption by SERS mapping. Scale bar, 1cm. 143
Figure 5.20. Fabrication process for engraving message via Au-S bonding of different Raman probe molecules. 144
Figure 5.21. Raman spectrum (a) and Raman mapping images plotted for the 1608 cm⁻¹ (b) and 999 cm⁻¹ (c) for SERS signal tuning via dielectric modulation... 145
Figure 5.22. Raman spectrum (a) and Raman mapping images plotted for the 1608 cm⁻¹ (b) and 999 cm⁻¹ (c) for SERS signal tuning via dielectric modulation... 146