B. D. F. Casse

Fabrication of 2D and 3D Electromagnetic Metamaterials for the Terahertz Range.

This paper addresses the 2D and 3D micro- and nanofabrication of ElectroMagnetic MetaMaterials (EM3) for the terahertz range. EM3 refers to artifbial composite materials which consist of a collection of repeated metal elements designed to have a strong response to applied electromagnetic felds, so that near resonance both the effective permittivity and magnetic permeability µ become simultaneously negative. This unusual situation leads to exotic consequences such as a negative index of refraction and an inverse Doppler and Cerenkov effect. EM3 fabricated so far have been mostly two-dimensional and in this respect are highly anisotropic. By anisotropic, it is inferred that the response of the system depends on the direction of illumination. The anisotropic nature of the metamaterials impedes eventual real-life applications of the negative media as it places constraints on the impinging electromagnetic waves. Ways of producing three-dimensional (3D) or more isotropic EM3 by means of tilted x-ray exposures will be introduced. Basic geometry tells us that if the structures are inclined at 30-45°, this would lead to an improvement of the coupling of the vector by 50-70%

Making and measuring nanostructures: Nanoscience and technology at the Singapore synchrotron light source

Synchrotron radiation facilities are natural places for nanoscience and technology as they may be used for both micro-and nanomanufacturing and the analytic characterization of nanoscale samples. The Singapore Synchrotron Light Source is conducting work in both fields. Examples given refer to the micro-and nanomanufacturing of the first electromagnetic metamaterials for the THz spectral range, the measurement of thin-film parameters such as thickness, density, and roughness in organic and inorganic nanoscale layer systems via X-ray reflectometry; the study of the atomic structure of the so-called carbon nanomesh that is formed through annealing of a SiC wafer at 1100°C by means of high-resolution X-ray photoemission spectroscopy; and the investigation of the chemical states of nanographite via X-ray absorption spectroscopy.

Industrial applications of micro/nanofabrication at Singapore Synchrotron Light Source

SSLS (Singapore Synchrotron Light Source) has set up a complete one-stop shop for micro/nanofabrication in the framework of the LIGA process. It is dubbed LiMiNT for Lithography for Micro and Nanotechnology and allows complete prototyping using the integral cycle of the LIGA process for producing micro/nanostructures from mask design/fabrication over X-ray lithography to electroplating in Ni, Cu, or Au, and, finally, hot embossing in a wide variety of plastics as one of the capabilities to cover a wide range of application fields and to go into higher volume production. The process chain also includes plasma cleaning and sputtering as well as substrate preparation processes including metal buffer layers, plating bases, and spin coating, polishing, and dicing. Furthermore, metrology using scanning electron microscopy (SEM), optical profilometry, and optical microscopy is available. LiMiNT is run as a research lab as well as a foundry. In this paper, several industrial applications will be presented, in which LiMiNT functions as a foundry to provide external customers the micro/nano fabrication services. These services include the fabrication of optical or X-ray masks, of micro/nano structures from polymers or from metals and of moulds for hot embossing or injection moulding.

Towards 3D Electromagnetic Metamaterials in the THz Range

SSLS has been using its lithography‐based micro/nanofabrication facility LiMiNT (Lithography for Micro and Nanotechnology) and its infrared spectro/microscopy facility ISMI to develop and characterize the first electromagnetic metamaterials having their spectral response in the THz range. Derived from Pendry’s nested‐split‐ring resonator design, these structures require micro/nanofabrication in order to have resonances in the THz range. They exhibit a negative refractive index and hold promise of sub‐diffraction limit imaging. Besides the reduction of the size of the resonating structures to extend the spectral range towards the visible, outstanding issues include the production of high‐aspect‐ratio resonators that are sensitive for the magnetic field in any direction (3D sensitivity) and the capability to produce copious amounts of the electromagnetic metamaterials with a good yield. In this paper, we shall report on first results of 3D EM3 structures made by inclined exposures.

X‐ray‐based Micro/Nanomanufacturing at SSLS — Technology and Applications

Deep and high‐aspect‐ratio micro/nanostructures can be accurately patterned in a variety of resists by proximity lithography using high energy, intense, parallel beams of X‐rays from synchrotron radiation sources. Using so called LIGA technology, high‐aspect‐ratio micro/nanostructures can be produced with vertical dimensions ranging from micrometers to millimeters and horizontal dimensions as small as microns. SSLS has set up its LiMiNT facility (Lithography for Micro/Nanotechnology) and is running it partly as a foundry, partly as a research lab. Under the foundry aspect, work is done for customers in various fields of applications. SSLS’ own research is focusing on the development of devices and artificial composite materials such as electromagnetic metamaterials. In this paper, the technology capabilities of the LiMiNT facility and application examples are presented.

Research Frontiers at SSLS

Singapore Synchrotron Light Source operates five experimental facilities for micro/nanomanufacturing and the characterization of materials and processes. Highlights of results include THz electromagnetic metamaterials, the elucidation of C bonds in the so‐called carbon nanomesh, and the high precision determination of the geometric parameters and the density of thin layers in multilayer systems.

Shaping And Characterising Materials — Recent Results From Singapore Synchrotron Light Source

SSLS offers facilities for micro/nanofabrication and the analytical characterization of devices, materials and processes. Selected applications are presented including the manufacturing of electromagnetic metamaterials for the THz spectral range up to the near infrared, core‐hole clock spectroscopy of the charge transfer from BBB and BFF molecules to an Au electrode, and the characterization of Co and ITO thin films.

NanoElectromagnetic Metamaterials Approaching Telecommunications Frequencies

Arrays of gold Rod-Split-Ring-Resonators with structural details down to sub 100 nm, and exhibiting electromagnetic metamaterial (EM3) behavior near telecommunications frequencies, have been produced by nanofabrication. Samples were characterized at the Singapore Synchrotron Light Source ISMI (Infrared Spectro/MIcroscopy) facility using Bruker Optics’ IFS 66v/S Fourier transform interferometer and Hyperion 2000 Microscope powered by synchrotron radiation. Oblique incidence transmission spectra were measured and revealed a spectral resonance around 190 THz. The present work extends the frequency range in which EM3are available, thereby opening up opportunities for new applications in the telecommunications frequency regime.