Fabrication and study of optical properties of multilayer metal-insulator-metal nanocups

VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY VU MINH THONG FABRICATION AND STUDY OF OPTICAL PROPERTIES OF MULTILAYER METAL – INSULATOR – METAL NANOCUPS MASTER’S THESIS Hanoi, 2019 VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY VU MINH THONG FABRICATION AND STUDY OF OPTICAL PROPERTIES OF MULTILAYER METAL – INSULATOR – METAL NANOCUPS MAJOR: NANOTECHNOLOGY CODE: PILOT RESEARCH SUPERVISORS: DR PHAM TIEN THANH PROF DR NGUYEN HOANG LUONG Hanoi, 2019 Acknowledgements First of all, I would like to express my sincere thank to my supervisors: Dr Pham Tien Thanh, and Prof Nguyen Hoang Luong, for their guidance, encouragement to completed this thesis Second of all, I would also like to thank Mr Nguyen Van Tien, and Mrs Nghiem Ha Lien, for their support in fabricating Polystyrene nanoparticles Third of all, I would like to express my sincere thank to my classmate Mr Pham Dinh Dat Thank to you, I got basic knowledge of FDTD method Thank you for your willing to help Forth of all, I would like to thank Vietnam Japan University and staff working here for their necessary supports Last but not least, I also would like to express my sincere thank to my family, for their fully support i TABLE OF CONTENTS Chapter 1: Introduction Research background 1.1 Surface plasmon resonance (SPR) 1.1.1 Theory 1.1.2 SPR in metal – insulator – metal (MIM) structure 1.2 Localized Surface Plasmon Resonance (LSPR) 1.2.1 Mie theory 1.2.2 LSPR in nanocups structure 1.3 Application of SPR and LSPR phenomena 1.3.1 Application of SPR phenomenon 1.3.2 Application of LSPR phenomenon 1.4 Finite Difference Time Domain (FDTD) approach 1.4.1 Theory 1.4.2 Calculation transmittance model of MIM nanocups structure Chapter 2: Experimental procedures 2.1 Fabrication 2.1.1 Polystyrene nanoparticles fabrication 2.1.2 Silane coupling preparation 2.1.3 Glass substrate treatment 2.1.4 Fabrication of monolayer Polystyrene nanosphere on glass substrate 2.1.5 Sputtering three layers Gold – Magnesium Fluoride – Gold on monolayer Polystyrene nanoparticles on a glass substrate 2.1.6 Dispersing MIM nanocups into water 2.1.7 Deposit sample onto Silicon wafer 2.2 Measurement Chapter Results and Discussion 3.1 SEM images 3.1.1 SEM images of monolayer polystyrene 3.1.2 SEM images of substrates after separate particles 3.1.3 SEM images of nanocups on Silicon wafer 3.2 Optical Properties 3.2.1 Optical properties of MIM nanocups structure on Glass Substrate 3.2.1.1 Confirmation of thickness of each layer 1 1 8 11 11 12 14 14 19 21 21 21 21 22 23 24 26 27 27 29 29 29 32 33 35 35 35 ii 3.2.1.2 Transmittance properties of samples on substrate 36 3.2.1.3 Transmittance properties of substrate after separate particle 39 3.2.2 Optical properties of MIM nanocups in water 41 Conclusion 44 References 45 iii List of Fig.s Fig 1.1 Fig 1.2 Fig 1.3 Fig 1.4 Fig 1.5 Fig 1.6 Fig 1.7 Fig 1.8 Fig 1.9 Fig 1.10 Fig 2.1 Fig 2.2 Fig 2.3 Fig 2.4 Fig 2.5 page Geometry for SPPs propagation at a single interface between metal and dielectric Metal – Insulator – Metal structure Dispersion relation of the fundamental coupled SPP modes of a silver/air/silver multilayer geometry for an air core of size 100 nm (broken gray curve), 50 nm (broken black curve), and 25 nm (continuous black curve) Also shown is the dispersion of a SPP at a single silver/air interface (gray curve) and the air light line (gray line) Models of semi-shell structures (a) Concentric-type semishell, (b) deposition type semi-shell without metal migration, (c) with metal migration (droplet-type semi-shell) Two dipolar plasmon mode in semi – shell, the transverse mode; b the axis mode (a) Schematic drawing of metal-insulator-metal (MIM) structure for biosensing application Layer is considered to be a detected biolayer An insulator film (layer 3) is sandwiched with two gold media (b) Optical setup for reflectivity measurement Reflectivity in the absence of layer 1, R0, is taken as reference Molecular interactions (biotin-avidin) detected using (a) MIM (0, 0), (b) MIM (10, 30), (c) MIM (10, 40), and (d) MIM (10, 55) substrates (Syahir et al) Spectra of the semi-shells obtained by simulation and experiment Optical density spectrum was obtained by experiment (solid line); extinction spectra obtained by calculation with k ¬ ez, E ¦ ez (dashed line), k ¦ ez, E ez (long dashed line), k Ư ez, E ¦ ez (dot-dashed line), and their average (dotted line) (R.Fujimura et al) 3D Yee cell showing the E and H field components MIM nanocups calculation model using FDTD method Preparation of Silane Coupling solution Glass substrate treatment Image of glass substrate after treatment by Silane Coupling Fabrication of monolayer PS nanoparticle on substrate Polystyrene nanoparticle attaches with the substrate through Silane Coupling 10 10 11 12 13 15 20 22 22 23 23 24 iv Fig 2.6 Fig 2.7 Fig 2.8 Fig 2.9 Fig 2.10 Fig 3.1 Fig 3.2 Fig 3.3 Fig 3.4 Fig 3.5 Fig 3.6 Fig 3.7 Fig 3.8 Fig 3.9 Fig 3.10 Fig 3.11 Fig 3.12 Fig 3.13 Fig 3.14 Fig 3.15 Procedure of making Multilayer Metal – Insulator – Metal nanocups structure on glass substrate and in water Sputtering multilayer Gold – Magnesium Fluoride – Gold on monolayer PS nanoparticles on glass substrate Dispersed particles into water by ultrasonic vibration, (a): substrate after separated particles, (b): MIM nanocups in water Deposit sample onto Silicon wafer Transmittance properties measurement of (a), Metal nanocups; (b), Metal – Insulator nanocups; (c), Metal – Insulator – Metal nanocups SEM image of monolayer Polystyrene nanoparticle with 200nm diameter SEM image of monolayer Polystyrene nanoparticle with 500 nm diameter SEM images of sample PS200MIM on substrate SEM images of sample PS500MIM on substrate SEM image of substrate of sample PS200MIM after separate particle SEM image of substrate of sample PS500MIM after separate particle SEM image of PS500MIM particle on Silicon wafer SEM image of sample PS200MIM particle on Silicon wafer Transmittance properties of Au thin film Transmittance properties of Au – MgF2 thin film Transmittance properties of Au – MgF2 – Au thin film Transmittance properties of PS200M (red straight curve), PS200MI (green straight curve), and PS200MIM (black straight curve) on glass substrate Transmittance properties of PS500M (red straight curve), PS500MI (green straight curve), and PS500MIM (black straight curve) on glass substrate Schematic of near-field coupling between metallic nanoparticles for the two different polarizations Transmittance properties of sample PS500MIM: before separate particle (red dashed curve), after separate particle (red straight curve); and MIM structure (green straight curve) 25 25 26 27 28 29 30 31 32 33 33 34 34 35 35 36 37 38 39 40 v Fig 3.16 Fig 3.17 Fig 3.18 Fig 3.19 Fig 3.20 Transmittance properties of sample PS200MIM: before separate particle (black dashed curve), after separate particle (black straight curve); and MIM structure (green straight curve) Transmittance properties of sample PS200MIM after separate particle (black straight curve), sample PS500MIM after separate particle (red straight curve) and MIM structure (green straight curve) Transmittance property of sample PS500MIM particles in water a, Image of PS200MIM particles in water; b, Transmittance property of sample PS200MIM particles in water Simulation result of transmittance properties of PS200MIM particle in air 40 41 42 42 43 vi List of abbreviations ATR: CTAB KPS: LSPR: MIM: PMMA: PS: PVD SDS: SEM: SPP SPR: Attenuated Total Reflection Cetyl trimethyl ammonium bromide Potassium Persulfate Localized Surface Plasmon Resonance Metal – Insulator – Metal Poly(methyl methacrylate) Polystyrene Physical Vapor Deposition Sodium Dodecyl Sulfate Scanning Electron Microscope Surface Plasmon Polariton Surface Plasmon Resonance vii ABSTRACT The Metal – Insulator – Metal (MIM) nanocups structure on glass substrate and in water were fabricated by chemical method and sputtering, studied by transmittance properties The morphology of the sample was studied by Scanning Electron Microscope, and transmittance properties were studies by UV-Vis-NIR, and simulated by Finite Difference Time Domain (FDTD) method The result showed that MIM nanocups have surface plasmon resonance (SPR) and localize surface plasmon resonance (LSPR) phenomena, that depend on size of Polystyrene (PS) and thickness of metal and insulator layers The purpose of this thesis is: - Deposit monolayer PS nanoparticles on glass substrate - Fabrication MIM nanocups structure with core of Polystyrene PS nanoparticles - Study SPR and LSPR phenomenon of Metal – Insulator – Metal nanocups structure on substrate and in water viii nanoparticle with diameter is 200 nm and 500 nm (call PS200MIM particle and Figure 3.5 SEM image of substrate of sample PS200MIM after separate particle Figure 3.6 SEM image of substrate of sample PS500MIM after separate particle PS500MIM particle respectively) are successfully removed from substrate 3.1.3 SEM images of nanocups on Silicon wafer Finally, Fig 3.7 and 3.8 were confirmed nanocups structure was made As the image is shown in Fig 3.7 and 3.8, the particle is separate In one individual particle, there is bright area which was predicted be Gold – Magnesium Fluoride – Gold nearly covers darker sphere shape area which was predicted be PS nanoparticle with diameter is 500 nm for sample PS500MIM particle and 200 nm for sample PS200MIM particle As shown in Fig 3.7 and Fig 3.8, the size is increase around 60 – 80nm, compared with size of PS nanoparticle The morphology of sample change from sphere to ellipse Therefore, multilayer MIM nanocups structure was made successfully 33 Figure 3.7 SEM image of PS500MIM particle on Silicon wafer Figure 3.8 SEM image of sample PS200MIM particle on Silicon wafer 34 3.2 Optical Properties 3.2.1 Optical Properties of MIM nanocups on Glass Substrate 3.2.1.1 Confirmation of thickness of each layer Transmittance (%) 60 Au(21nm) experimence 50 40 30 Glass Substrate 20 Au(21nm) simulation 10 300 400 500 600 700 Wavelength (nm) 800 Figure 3.9 Transmittance properties of Au thin film First, thickness of each layer was determined by fitting results of transmittance properties from measurement of thin films: Gold (M), Gold – Magnesium Fluoride Transmittance (%) 60 50 40 Au (21nm) – MgF2(38nm) 30 simulation 20 Au(21nm)-MgF2 (38nm) 10 experiment Glass Substrate 300 400 500 600 700 Wavelength (nm) 800 Figure 3.10 Transmittance properties of Au – MgF2 thin film 35 Transmittance (%) 60 Au(21nm) – MgF2(38nm) – 50 Au(19nm) experience 40 Au(21nm) – MgF2(38nm) – experiment 30 Au(19nm) simulator 20 Glass Substrate 10 300 400 500 600 700 800 Wavelength (nm) Figure 3.11 Transmittance properties of Au – MgF2 – Au thin film (MI) and Gold – Magnesium Fluoride – Gold (MIM) and result of transmittance properties from simulator by using transfer matrix (Fig 3.9; Fig 3.10; Fig 3.11) As we can see in three Fig.s: Fig 3.7; Fig 3.8; Fig 3.9, the results from measurement transmittance properties of M, MI, MIM nearly fit their result from simulator Therefore, the thickness of each layer is: first layer is 21 nm Au, second layer is 38 nm MgF2 and final layer is 19 nm Au 3.2.1.2 Transmittance properties of samples on substrate Now, we analysis transmittance properties of sample PS200MIM and PS500MIM which are shown in Fig 3.12 and Fig 3.13 respectively As we can see, for sample using PS nanoparticle with diameter is 200 nm, peak of PS200M is 560 nm, percentage of transmittance is 33% compare to peak of Gold thin film with the same thickness (21 nm) which have peaked at around 530nm and transmittance percentage is about 48% Therefore, the existence of PS nanoparticle in sample cause this red shift This phenomenon is continued when sputtering 38 nm MgF2 on sample 36 PS200M, the peak is red shift to around 580nm and the transmittance properties increase by 3% However, when final layer (19 nm gold layer) sputtering on sample 40 Transmittance (%) PS200MI PS200M 30 20 PS200MIM 10 300 400 500 600 Wavelength (nm) 700 800 Figure 3.12 Transmittance properties of PS200M (red straight curve), PS200MI (green straight curve), and PS200MIM (black straight curve) on glass substrate PS200MI, blue shift occurs, from peak at 580nm to peak at approximate 520nm with transmittance properties sharply decrease from 36% to about 15% (more than half) We can predict that there is another peak in wavelength longer than 800nm Fig 3.13 showed transmittance properties of sample using PS nanoparticle with diameter is 500 nm as core For sample PS500M, with existence of PS nanoparticle, there are peaks The first one is at 540nm, and second one at 740nm with transmittance property is 16% and 15%, respectively Sample PS500MI also has two peaks as sample PS500M The peak at 540nm red shifts to 560nm and transmittance property goes down by 2% The second peak at 740nm shifted to 760nm, and transmittance property dramatically increases to 16% When the final layer (19 nm gold) was sputtered on the sample, the transmittance property of sample 37 20 Transmittance (%) PS500MI 15 PS500M 10 PS500MIM 300 400 500 600 700 Wavelength (nm) 800 Figure 3.13 Transmittance properties of PS500M (red straight curve), PS500MI (green straight curve), and PS500MIM (black straight curve) on glass substrate significantly decreases by 5.5% for a peak at 510nm and 10% for a peak at around 710nm The second peak of the sample can be explained as LSPR is occurred in here, also the interaction between neighbor particle [9] Those phenomena can be explained as follow The second peak of sample PS500MIM maybe peak of LSPR of the sample Using the simple approximation of an array of interacting point dipoles, the direction of the resonance shifts for in-phase illumination can be determined by considering the Coulomb forces associated with the polarization of particle [11] As Fig 3.14, the restoring force acting on the oscillating electrons of each particle in the chain is either increased or decreased by the charge distribution of neighboring particles Depending on the polarization direction of the exciting light, this leads to a blue-shift of the plasmon resonance for the excitation of transverse modes, and a red-shift for longitudinal modes 38 Figure 3.14 Schematic of near-field coupling between metallic nanoparticles for the two different polarizations In conclusion, multilayer Metal – Insulator – Metal nanocups structure on glass substrate enhance SPR and LSPR signal dramatically 3.2.1.3 Transmittance properties of substrate after separate particles After separate particles from sample PS500MIM and PS200MIM, transmittance properties of samples were also studied Fig 3.15 showed transmittance property of sample PS500MIM before and after separate particle, also compare with MIM structure with the same thickness As Fig presented, transmittance property sharply increased to around 42% at peak around 510nm, and second peak at around 720nm disappeared It can be explained as after separate particle from sample, create MIM structure with holes Therefore, LSPR phenomenon did not occur lead to the disappearance of the second peak at 720 nm, and only display characteristic of normal MIM thin film structure Also because of holes, the transmittance property is higher than the transmittance property of MIM structure by 20% Transmittance properties 39 of sample PS200MIM after separate particle rocketed by more than 40%, higher than Transmittance (%) 40 30 20 10 300 400 500 600 700 Wavelength (nm) 800 Figure 3.15 Transmittance properties of sample PS500MIM: before separate particle (red dashed curve), after separate particle (red straight curve); and MIM structure (green straight curve) Transmittance (%) 60 50 40 30 20 10 300 400 500 600 700 Wavelength (nm) 800 Figure 3.16 Transmittance properties of sample PS200MIM: before separate particle (black dashed curve), after separate particle (black straight curve); and MIM structure (green straight curve) MIM structure by 30% (Fig 3.6) This phenomenon can be also explained as same 40 as explanation for this phenomenon of sample PS500MIM Comparison of transmittance properties samples PS200MIM and PS500MIM and MIM structure illustrated in Fig 3.17 According to Fig 3.17, after separate particle, both samples PS200MIM and sample PS500MIM have the peak at the same position as the peak of MIM structure (approximately 520nm), with transmittance Transmittance (%) 60 50 40 30 20 10 300 400 500 600 700 Wavelength (nm) 800 Figure 3.17 Transmittance properties of sample PS200MIM after separate particle (black straight curve), sample PS500MIM after separate particle (red straight curve) and MIM structure (green straight curve) property is about 55%, 42%, and 22%, respectively In conclusion, MIM nanocups on glass substrate have both SPR and LSPR phenomenon from MIM structure and sphere structure 3.2.2 Optical properties of MIM nanocups in water Transmittance properties of sample PS500MIM particle in water was showed in Fig 3.18 Difference with this sample on the substrate, transmittance curve of PS500MIM particle in water have not a single peak from range of wavelength from 41 Transmittance (%) 80 75 70 65 60 300 400 500 600 700 Wavelength (nm) Figure 3.18 Transmittance PS500MIM particles in water property 800 of sample 300nm to 800nm We can predict that peak of transmittance of sample shift to near – 75 a Transmittance (%) b 70 65 60 55 50 45 300 400 500 600 700 Wavelength (nm) 800 Figure 3.19 a, image of PS200MIM particles in water; b, Transmittance property of sample PS200MIM particles in water Infrared area The transmittance property of sample is very high (around 78%) Sample PS200MIM particle in water has two peaks from incident light wavelength 42 from 300nm to 800nm (Fig 3.19) As transmittance property curve is shown in Fig 3.19b, there are two peaks at about 540nm and around 730nm Maybe because the density of PS200MIM particle in water is low, therefore, the signal is not clear (Fig 3.19a) The simulator of PS200MIM particle in air, using FDTD method was done with the set up as same as calculation model in the introduction (Fig 3.20) In result of simulation, the first peak is around 480nm and the second peak is around 700nm, difference with experience result (540nm and 740 nm) The difference is because of Transmittance (%) reasons The first reason is the simulator was done in air with refractive index 1, 80 60 40 300 400 500 600 700 Wavelength (nm) 800 Figure 3.20 Simulation result of transmittance properties of PS200MIM particle in air while the experience was in water with refractive index 1.33 The second is the structure use in simulation is a bit difference with the real, therefore, the result of simulator was different from result of experience, also the difference between the refractive index of gold used in calcuation and refractive index of gold in experience The final reason is in simulation, only structure was calculated, in the specific direction, while in experience, there are many particles, with difference structure, and in difference direction 43 CONCLUSION In this thesis, we successfully made nearly monolayer Polystyrene nanosphere on glass substrate We successfully fabricated Gold – Magnesium Fluoride – Gold nanocups structure with core of 200 nm and 500 nm diameter of Polystyrene nanoparticle In case of sample PS – Gold – Magnesium Fluoride – Gold on the substrate, the plasmonic properties of sample increase when sample has Metal – Insulator – Metal nanocups structure For more detail, for sample PS200MIM, the transmittance properties of sample sharply decrease, when compared with transmittance properties of sample PS200M (by 18%) and the peak is blue shift from 530nm to 520nm For sample PS500MIM, the transmittance curve appeared peaks at 510 and 710 nm (which cause by LSPR phenomenon), the transmittance properties dramatically went down In case of sample PS – Gold – Magnesium Fluoride – Gold in water, the 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