Fabrication and characterisation of multilayer thin film using self assembly of colloidal gold and silica nanoparticles | |
| Author | Khan, Zaheer Abbas |
| Call Number | AIT Diss. no.ISE-12-12 |
| Subject(s) | Thin film, Multilayered Nanoparticles |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Microelectronics Engineering |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ISE-12-12 |
| Abstract | A novel approach of multilayered thin film based on layer - by - layer deposition using colloidal nanoparticles was carried out in this work. The films were made by the self - assembly of oppositely charged metal and dielectric nanoparticles, alternately capped with polymers. Synthesized colloidal suspensions of gold nanoparticles (~20nm) and silica nanoparticles (~30nm) were us ed as the building blocks for the self - organisation of the films. Capping with PDDA and chitosan was used effectively to control the optical absorption of the surface plasmon resonance peaks of the gold nanoparticles. Using different combinations of layer formation, absorption characteristics in the near - ultraviolet (NUV), green and blue region were controlled through capping and varying the thickness of the film. Capping with chitosan or PDDA reduced the absorption peak of the coated silica nanoparticles i n a similar fashion. Peak absorption in the UV range was achieved by assembling bare silica nanoparticles layers onto layers of gold nanoparticles. Transmission color was controlled (less than 1% color distance per added bi - layer) by changing the film thic kness. Optical modeling of multilayer thin films constructed with oppositely charged nanoparticles helped us to understand phenomenon such as surface plasmon resonance, absor bance, transmittance and reflectance . Maxwell - Garnett effective medium theory in this case is applied in quasi - static limit to multilayer composite consisting of host material silica and inclusion material gold nanoparticles. Maxwell Garnett optical simulations is correlated with experimental spectra obtained for the thin film composit es. The thickness of layers, size and spacing of metal inclusion is varied to alter the optical properties for the required device applications. The multilayered thin film of gold and silica resembles a structure consisting of large charge sheets of metal separated by a dielectric layer. When the ap plied electric potential reaches a threshold value, it drives the electrons to tunnel through the charge sheets producing a rectification effect. Therefore c urrent - voltage measurements of the multilayer thin film s were performed to calculate the threshold voltages. The electrical capacitance in these multilayer devices was modified with the change in thickness of the dielectric layers between two conducting layers and calculated by capacitance - voltage measurements of multilayer stack. I - V measurements were also measured with a change in temperature of the multilayer films at any fixed voltage. Fowler - Nordheim plots applied to current - voltage characteristics were helpful in determination of the tunneling behavior of thin Au - SiO 2 films. Electron micrographs provided the particle size distribution for the colloidal nanoparticles and determination of the thickness and particle arrangement in the multilayered films. |
| Year | 2012 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ISE-12-12 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Department of Industrial Systems Engineering (DISE) |
| Academic Program/FoS | Industrial Systems Engineering (ISE) |
| Chairperson(s) | Dutta, Joydeep |
| Examination Committee(s) | Bohez, Erik L.J. ;Hornyak, G. Louis ;Mohammed, Waleed S. |
| Scholarship Donor(s) | Higher Education Commission (HEC), Pakistan |
| Degree | Thesis (Ph. D.) - Asian Institute of Technology, 2012 |