Development of Heat Treatment for Single-Crystallizing Polycrystalline Gold Nanostructures

Project: National Science and Technology CouncilNational Science and Technology Council Academic Grants

Project Details

Abstract

Various gold nanostructures are applied for the biosensors and photonic integrated circuit (PIC) fabricated by the vapor-deposition and focused ion beam or electron beam lithography. For example, long-range surface plasmon polariton waveguides have been used for the biosensors. However, due to the high attenuation of polycrystalline gold nanostructure, the sensitivity cannot be improved. Although the thermal annealing can be used to improve the crystallinity and reduce the defeats and grain boundaries of metal, some components of devices are not available in high-temperature oven. On the other hand, another technique was developed to use FIB/EB milling on a large-area single-crystalline Au plate, fabricated by chemical method. Recently, we found that the mild plasmonic heating of NIR laser annealing on polycrystalline gold nanowires in water at room temperature can cause their recrystallization and then produce single-crystalline nanowires with different cross sections of tetragonal, pentagonal, and hexagonal. Based on these finding, we propose a three-year project of using laser annealing process to recrystallize the polycrystalline gold nanowires in water at room temperature and atmospheric pressure. The method can cause their recrystallization and then produce single-crystalline nanowires. The process conditions (laser power, fluence, exposure time, wavelength, polarization) and the heating profile will be optimized, including the cooling rate. The first year: Taser annealing microscopy will be developed. Polycrystalline gold nanowires will be fabricates by focus ion beam milling. The optimal laser annealing profile will be developed. The FE-SEM is used to measure the morphology of nanowires, and then HR-TEM and XRD are used to measure the crystallinity of these nanowires before and after laser annealing. For the short nanowires, the dark-field spectrometer and EELS will be used to measure the multipole modes of longitudinal surface plasmon resonance, and then the Q-factor will be identified. The second year: Polycrystalline array dimer antenna nanostructure will be fabricates by focus ion beam milling. The optimal laser annealing profile will be developed. The FE-SEM is used to measure the morphology of nanostructures, and then HR-TEM and XRD are used to measure the crystallinity before and after laser annealing. The dark-field microscopy/spectrometer and EELS will be used to measure the plasmon mode of antenna, and then the Q-factor will be identified. The scanning laser annealing microscopy system will be developed. The third year: Polycrystalline gold strip waveguides will be fabricates by focus ion beam milling, and the scanning laser annealing microscopy system will be used for large-area gold film (e.g. strip waveguides) recrystallization. The optimal laser annealing profile will be developed. The FE-SEM is used to measure the morphology of nanostructures, and then HR-TEM and XRD are used to measure the crystallinity before and after laser annealing. The AFM will be used to measure the surface roughness. The propagation attenuations of the strip waveguides before and after annealing will be measured to identify the Q-factor. This technology can be applied to improve the performance of Au, Ag and Al nanostructures for the applications of biosensors and PIC.

Project IDs

Project ID:PB10708-1789
External Project ID:MOST107-2221-E182-035
StatusFinished
Effective start/end date01/08/1831/07/19

Keywords

  • Single crystalline nanowire
  • polycrystalline
  • annealing
  • recrystallization
  • heat treatment
  • photothermal
  • plasmonic heating
  • crystallinity
  • propagation loss

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