Diffraction efficiency of plasmonic gratings fabricated by electron beam lithography using a silver halide film

Abstract

The silver nanoparticle surface relief gratings of ∼10 μm period are fabricated using electron beam lithography on the silver halide film substrate. Morphological characterization of the gratings shows that the period, the shape, and the relief depth in the gratings are mainly dependent on the number of lines per frame, the spot size, and the accelerating voltage of electron beam raster in the SEM. Optical absorption of the silver nanoparticle gratings provides a broad localized surface plasmon resonance peak in the visible region, whereas the intensity of the peaks depends on the number density of silver nanoparticles in the gratings. The maximum efficiency of ∼7.2% for first order diffraction is observed for the grating fabricated at 15 keV. The efficiency is peaking at 560 nm with ∼380 nm bandwidth. The measured profiles of the diffraction efficiency for the gratings are found in close agreement with the Raman-Nath diffraction theory. This technique provides a simple and efficient method for the fabrication of plasmonic nanoparticle grating structures with high diffraction efficiency having broad wavelength tuning.

Plasmon-enhanced diffraction in nanoparticle gratings fabricated by in situ photo-reduction of gold chloride doped polymer thin films by laser interference patterning

“…This effect, called plasmon-enhanced diffraction efficiency, is attributed to the plasmonic nanoparticles present in the film. A similar behaviour has only been reported recently in the literature 23 , but never with such a spectral matching between plasmonic properties and diffraction efficiency that is observed here. We note that regardless of the spectral profile matching, it seems that the diffraction efficiency is higher in the case where nanoparticles are present at the film surface.…”

“…We observe a significant difference in the PNG we obtain as compared with those obtained with pulsed laser patterning, which is the formation of a surface relief grating after nanoparticle growth. As will be seen below, such fabricated PNG present unusual optical properties such as plasmon-enhanced diffraction 23 . This article is organized as follows: In the next section we describe the fabrication technique and the experimental setups.…”

Customizing plasmonic diffraction patterns by laser interference

“…In the case of periodic structures without topography, such as patterns analyzed here, the ratio between transformed and nontransformed regions and their optical properties determines the diffraction efficiency. 21,42 The former can modify the relative efficiency between different diffraction orders and the latter denes the optical contrast between the fringes. This last parameter is particularly relevant in these fringes since the optical constants of the alloy NPs are very different from those of as grown regions.…”

“…20 Electron beam lithography allows the production of well-dened nanostructures but it is time consuming. 21 Furthermore, lithographic techniques are multiple-step processes that require the use of resin in contact with the surface. Laser techniques for structuring metal surfaces involve direct laser writing or laser interference.…”

Femtosecond laser fabricated polymeric grating for spectral tuning

“…In this study, gratings with an epoxy-based negative photoresist (SU-8) are fabricated by direct writing with a Ti:sapphire femtosecond laser at a wavelength of 800 nm, a pulse width of 67 fs, and a repetition rate of 80 MHz (Libra system, Coherent Inc.). Conventional techniques to fabricate diffraction gratings include photo-masking [21], electron beam lithography [22], etching techniques [23], and holographic interference [24,25]. Holographic lithography/recording was developed to create periodic 3D microstructures, in which periodic interference patterns such as an aspheric microlens structure [26], microscopic tubular structure [27], and fast bits [28], are printed into the photoresist by multi-laser beam irradiation.…”