The Study Of The Metamaterial Absorber Using Disorder Structures And Heavily Doped Semiconductors

Photon or electromagnetic wave has been playing important role along with the development of peoples‘ society. With the advance of the modern science and technology, the controlling of the behaviors of photons reaches a new height. One of the key objectives in the photon modulation and application research is how to absorb all the incident photons. Recently, metamaterial absorber with artificial subwavelength structures by the support of effective media theory, attract great attentions on its significant function and tremendous application potential in energy harvesting, surface enhanced Raman scattering, nonlinear optics, sensors, detectors, stealth technology, thermal emitters, imaging technology, communication technology. Generally, metamaterial use the noble metals with periodic subwavelength structure to achieve the perfect photon absorption. Nevertheless, for the visible realm, the constituents of the metamaterial absorber with the subwavelength structure should be on the order of tens of nanometers which propose many challenges for the large-scale and low cost manufactures of the metamaterial absorber. Moreover, the underlying absorption mechanism of the metamaterial absorber is the plasmonic resonance which always needs noble metal to provide enormous free electrons, but the unmodifiable permittivity of the noble metal puts a severe limitation on the modulation and application of the metamaterial absorber. We investigate the feasibility to overcome the two limitations described above in the area of the metamaterial absorber and coupling plasmonics. The disorder/random structures and the heavily doped semiconductor were used to realize the near perfect absorption in the visible to the near infrared realm,respectively. The coupling plasmonics in the disorder structure and the heavily doped semiconductor were introduced to be induced by the forced motions of the free electrons. The main contents and progress of the paper are shown below:First, we study the feasibility about achieving the metamaterial absorber by the random structure to substitute the periodic structure, investigate the underlying mechanism of the random structure absorption, and realize the ability to tuning the absorption properties. The researches show that the tunable absorption in the visible realm can reach over 99% by the Ag film/oxide dielectric film/random Au nanoparticle arrays, confirming the metamaterial absorber can be random structures. Next, the near perfect absorption properties are tuned through adjusting the thickness and dielectric constant of the oxide dielectric film by the atom layer deposition and changing the distributions of the random Au nanoparticle arrays; we investigat the mechanism of tuning process and established the laws of the tuning process; we fabricat the random structure on the roughness substrate which achieved a broad band near zero reflection. The results reveal that the absorption peak located at the high frequency was caused by the destructive interference from the Ag film/oxide film bilayer with the Au nanoparticle enhanced the absorption while the low frequency absorption peak was from the coupling between the Au nanoparticle and the Ag film; The changing of the permittivity of Ag film will influence the destructive interference induced absorption peak very much but has little effect on the coupling induced absorption peak.Next, we fabricate the disorder metamaterial absorber on the transparent substrate with a inversed structure, and research the mechanism of the transition of the coupling plasmonics along with the increasing of the dielectric layer thickness. The researches show that the tunable absorption can reach over 96% when the light entering through the transparent substrate into the inversed metal film/oxide dielectric layer/random Au nanoparticle structure, which confirms superior absorption of the inversed ?amorphous‘ metamaterial absorber. Then, by taking advantage of the inversed fabrication process, by comparing before and after the top metal film coating on, the influence of the top Au film on the absorption properties of the localized surface plasmon resonance(LSPR) absorber has been studied with modulation of the dielectric layer thickness which can be accurately controlled with the help of ALD.The different effects from the different metal film on the LSPR absorption of the Au nanoparticles were investigated. The results show that as the thickness of the oxide dielectric layer increased, the coupling between the metal film and the Au nanoparticles become weaker, and the destructive interference govern the absorption;Besides, if on the same condition of the constant thickness of the oxide dielectric layer, a metal with high plasma frequency will couple with the Au nanoparticle more easily than the one with low plasma frequency.At last, we research the feasibility about achieving the near perfect absorption by adoption of heavily doped semiconductor to replace the metal film in the metamaterial absorber, and investigate the free charge carriers force motion model to explain the coupling plasmonics in the heavily doped semiconductor. The results show that the aluminum heavily doped zinc oxide(AZO) film deposited by ALD is a good plasmonic material in the near-infrared realm, and the absorption of fabricated AZO/Zn O multi periodic layers can be over 99% in the near-infrared realm; Next, we utilized the numerical simulation to design different metamaterial structure based on the AZO material to investigate the coupling plasmonics effect in the AZO based structure and establish the forced motion model of the free electros. The results indicate that the coupling plasmonic phenomenon can be existed in the AZO material. The coupling plasmonic can be explained as the electromagnetic field driven the free carrier to realize the current and anti-parallel motion which lead to a kind of the magnetic resonance. The energy of the plasmonics will be transformed to the heat energy through the damping oscillation.