Preparation And Applications Of Submicron Metal Structures Using Microfabrication Technique

Due to the unique optical properties from the visible to the infrared region, submicron metal structure arrays (SMSA) can be used as the optical enhanced substrate for SERS (Surface-enhanced Raman scattering) or SEIRA (Surface-enhanced infrared absorption) to improve the detecting sensitivity of Raman scattering spectrum or Infrared absorption spectrum. Therefore, convenient and repeatable methods of fabricating SMSA SERS/SEIRA substrates have been a research focus in recent years.Currently, a variety of methods for fabricating SMSA SERS/SEIRA substrates are available. For example, chemical synthesis, as a simple and effective method, is widely used to fabricate SMSA. However, due to the huge randomness in size, shape, and inter-particle spacing, chemical synthesis is limited to the experimental stage. In order to overcome the limitations of chemical synthesis, electron beam lithography technology (EBL) is used to fabricate metal nanostructure with highly controlled fine patterns, but it needs costly instrument and has low throughput rates and small overall writing areas. Compared to EBL, deep-ultraviolet contact lithography technology (DUV Lithography) is recognized as a simple and cost-effective approach for the fabrication of SMSA. However, due to its limited resolution, DUV Lithography is not directly suitable for the fabrication of metal nanostructure with’hot spots’. Other methods of synthesizing noble metal nanoparticles onto substrates are electroless deposition and electrochemical deposition.In this work, through combining the DUV Lithography with electrodeposition, interference lithography technology and isotropic etching technology, several SMSAs have been fabricated as SERS/SEIRA substrates. A highly-ordered, uniform dendritic silver nanocomplex array with sunflower-like structure was fabricated as SERS substrate, and exhibited good performance for measurement of4-aminothiophenol (4-ATP). Also, the relationship between the substrate morphology and Raman enhancement effect was examined. In addition, Raman mapping results confirmed the excellent reproducibility in the SERS measurement with this SERS substrateNitrite is a widespread inorganic nitrogen species in natural environments, and receives concerns in food industry and water pollution control field. In this thesis, a new SERS detection method for nitrite in aqueous solution with the self-made dendritic silver nano-complex array as the SERS substrate was proposed,. The Raman peaks of nitrite at c.a.817cm-1was used to quantify the nitrite. This method was demonstrated to be a new detection method for nitrite in aqueous solution.As detailed molecular structural information could be extracted by infrared absorption spectroscopy in a label-free fashion, it can be used as a powerful analytic tool. SMSA could be used as substrates to enhance both SERS and SEIRA measurement. In this work, the interference lithography (IL) was combined with DUV to fabricate SMSA. With the Fresnel diffraction nearby the mask surface, a submicron multiple concentric-ring structure array could be fabricated using a simple hole array mask by only one-step exposure. According to angular spectrum transmission theory, the formation mechanism of submicron multiple concentric-ring structure was explored with numerical simulations. Various submicron multiple concentric-ring structure arrays with fine nanostructures were fabricated on different substrates. A unique response in Infrared band region of the submicron multiple concentric-ring structure was also obtained.In order to prepare SMSA with a larger process tolerance, the broadening in an isotropic etching process was employed to fabricate a metal annulus gap array with continuously adjustable gaps from70～800nm. A resonance peak, origining from the annulus gap, was observed in an infrared spectroscopy microscope, which indicates that this metal annulus gap array could be used for SEIRA studies. In addition, a series of Frequency selective surfaces for far-infrared light were fabricated on Si wafer by DUV Lithography. The relationship between their structural features and spectral response was also explored.