Double Negative Properties In Metal-dielectric System

In recent years, double negative material (DNM) has attracted more and more attention due to their potential application in many fields, such as communication, military. As we know, the response of a material to electromagnetic (EM) waves is largely determined by only two parameters:permittivity (ε) and permeability (μ). In DNM, both permittivity (s) and permeability (μ) have a negative value. When the EM wave propagates in DNM, the electric field (E), magnetic field (B), and wave vector (k) follow a left-hand rule, which is quite different from the conventional materials. The research of DNMs has rapidly grown and blossomed since J. Pendry’s famous prediction of perfect lens beyond the diffraction limit, which is based on the negative refraction in DNM. In this paper, we are using both composites and metamaterial to achieve double negative properties.Metal/dielectric composites have been studied for centuries as the structural material, the metal particles distribute in the dielectric matrix can improve the mechanical properties of the material. In recent years, its potential application in functional material field has attracted more attention in the worldwide, especially in the electromagnetic field. But the mechanism of composite’s EM properties is still not clear enough. In order to get a better understanding of the double negative properties in composite, it is essential to study the basic physical properties of each component and the mechanism responsible for its EM behaviours.Metamaterial is a kind of artificially structured material which obtains its properties from the unit structure rather than the constituent materials. It has been well studied since the beginning of this century as it has a periodic structure. The EM properties in metamaterial can be well described by the Maxwell’s equations. The mechanism of the double negative properties in metamaterial is very clear based on the theoretical calculation and experiment. However, the metamaterial still stay in the lab as the cost of metamaterial’s fabrication cannot be afforded by the commercial company. Therefore, to reduce the cost of the fabrication is the key point to bring metamaterial into our real life.The purpose of this paper is to get a better understanding of the double negative properties in composite and reduce the cost of metamaterial’s fabrication. In order to achieve this goal, it is essential to study the basic physical properties of each component and the mechanism responsible for their EM behaviours. Both of them will be discussed in this paper.1. Metal/dielectric compositesWe use a selective reduction reaction to fabricate a new kind of dual composite in one step. The dual composite can be described as a composite-within-a-composite. By controlling the parameters of the selective reduction process, such as reduction temperature and time, we can adjust the content of the conductive phase, the size of the metal particles, and also control the microstructure of the composite. Therefore, we can get tunable EM properties to obtain both negative permittivity and negative permeability in the GHz range. The mechanism responsible for the dual composites’ permittivity behaviour can be well described by the effective medium theory (EMT). The calculation based on EMT shows a good agreement with the experiment results, which is suggest the EM properties of metal/dielectric composite have a close relationship with its microstructure.2. MetamaterialAs we know, the structural units of a metamaterial, known as meta-atoms or meta-molecules, must be substantially smaller than the wavelength being considered, and the average distance between neighbouring meta-atoms is also subwavelength in scale. If we want to fabricate a kind of metamaterials, which can be used in infrared or visible light range, based on the discussion above, we should keep the size of the units in um or nm range. Most of the metamaterials in this frequency range are fabricated by lithography or focus ion beam etch, combined with deposition. That is the reason of the high cost of the fabrication. In this paper, however, we combine the pulsed laser deposition (PLD) system with shadow mask to fabricate metamaterial. By using metallic mesh as the shadow mask, we successfully reduce the cost of the metamaterial’s fabrication. This method can be not only combined with the PLD, but also with chemical vapor deposition (CVD), physical vapor deposition (PCD), etc., which has a potential application in commercial fabrication.