| Optical antenna has been widely investigated due to their novel optical phenomena and capability of manipulating light field at the nanometer scale. It has been used in many fields such as nano-scale light manipulation, surface enhanced Raman spectroscopy (SERS), fluorescence enhancement, near-field imaging and near-field optical nanolithography. Its properties are based on the localized surface plasmons (LSPs) that are supported by metal nanoparticles or nanostructures. In our work, two kinds of antennas consist of LSPs coupling structures were designed for SERS experiments, which can significantly increase the Raman signals due to the excitation and radiation enhancement of the molecules. On the other hand, based on the localization property, near-field optical nanolithography was investigated using bowtie aperture antennas. We studied the optical near-field properties of the bowtie aperture antenna and established a nanolithography system. To improve the lithography resolution and quality, interferometric-spatial-phase-imaging (ISPI) technique was introduced into this system, and finally assisted to realize high-throughput parallel near-field scanning optical lithography with diffraction-unlimited resolution. Our work has great potentials on developing easy-fabricated and low-cost SERS substrates and high-resolution, high-throughput, low-cost and reliable nano-manufacture technologies.The details of this thesis are shown as following:1. Ag nanocap-nanohole coupling antenna was designed for SERS experiments. This structure was fabricated through a facile and low-cost method. Both the SERS measurements and numerical simulations show that the cap-hole structure produces much stronger Raman signal than the non-coupling structures which is due to the plasmonic coupling effect within the gap between the cap and the hole. The coupling effect localized the energy in the gap so that can produce more "hot spots" and higher SERS enhancement factor. Additionally, the coupling effect is sensitive to the gap size, which can be controlled by the Ag layer thickness during the evaporation process. It provides an effective way to control the SERS performance for further applications.2. A quasi-3D system composed of Ag nanocubes and Ag nanohole arrays was designed and fabricated. The Ag nanocubes were synthesized through chemical reaction. The Ag nanohole arrays were obtained by evaporating Ag onto anodic aluminum oxide (AAO) templates, which have self-organized hexagonally-ordered hole arrays. PMMA film with nanoscale thichness was used as a spacer layer to separate the cubes and the hole array. SERS measurements and numerical simulation show that this structure supports LSPs coupling effect within the spacer. The intense local field can affect the excitation and radiation of Raman molecules doped in PMMA, which produced1.1×108SERS enhancement. A series of experiments were performed to investigate the sensitivity of the coupling effect to the structure parameters (such as the spacer thickness, the Ag film thickness, the hole diameter and the hole period). It provides varies ways to modulate the SERS performance of this kind of structure.3. Near-field scanning optical nanolithography was studied using bowtie aperture antennas. The near-field optical properties of the bowtie antenna were investigated for the reference of the mask design, the alignment procedure and the lithography technique. A near-field scanning optical lithography system was established using bowtie antennas as focusing elements. The effects of experimental parameters such as the photoresist properties, exposing source, scanning speed and the lubricant were analyzed through experiments. After optimizing the parameters,1D and2D arbitrary patterns with diffraction-unlimited resolution (78nm and106nm, respectively) were achieved under visible exposing light.4. To improve the throughput of near-field scanning nanolithography, parallel lithography technique was studied. Interferometric-spatial-phase-imaging (ISPI) technique was introduced into the lithography system to realize accurate gap detection and alignment. Through the ISPI alignment for the mask and photoresist substrate,0.02mrad parallelism can be achieved. The ISPI technique was also utilized to establish a feed-back system to suppress the noise during lithography process, which improved the stability of the whole system. The experimental setup and mask structure is developed according to the ISPI-assistant lithography strategy, and the working distance of the antennas can be well controlled to achieve a lithography resolution as small as19nm. High-throughput parallel near-field nanolithography using massive antenna arrays (e.g.25and1024antennas) were successfully realized with good quality, uniformity and reliability. By additionally speeding up the scanning movement, the throughput can be further increased to104times higher than the traditional near-field scanning lithography technique. The innovations of this thesis are listed following:1. Based on the local field enhancement of the LSPs coupling effect, Ag nanocap-nanohole coupling antenna was designed for SERS. The fabrication of this structure is facile and low-cost, and is able to control the gap size through the thickness of the Ag layer, which provides a easy way to modulate the SERS effect of this kind of structure.2. A quasi-3D plasmonic coupling antenna structure which is consist of Ag nanocubes and Ag nanohole arrays was realized using a PMMA film as spacer layer. An idea was performed to use Ag nanohole array to increase the absorption of the incident light energy and localize it in the coupling area. While the Ag cubes can enhance the radiation of the Raman signal and transfer it to far field for detection. This structure produced1.1×108SERS enhancement.3. Near-field scanning optical nanolithography using bowtie aperture antannas was studied thoroughly by investigating the influence of each technical parameter. ISPI technique was introduced into the lithography system to detect the distance between the mask and photoresist substrate and align them with a high accuracy (0.02mrad) so that the problems caused by the near-field property of the antenna can be solved. The ISPI technique can precisely control the working distance of the antenna, which helps to achieve a lithography resolution as small as19nm and finally realize massive parallel lithography for1D and2D arbitrary patterns. The throughput can reach104times of the traditional near-field lithography method. |
PDF Full Text Request