奈米結構超物質之新穎特性研究(I)

Abstract

在這裡我們提出的計畫是奈米科技中一個極富挑戰性的新課題---「奈米結構的群體效應 (Collective behavior)和崁入人造奈米物件後的新材料研究」。超物質(metamaterial)是一種人造結構的混 合材料。這種材料具有許多自然界中沒的特性。結合了奈米科技，超物質將更能展現其優異的性質。 這些特質包括負折射係數，包括負折射係數、電磁波和聲波的傳輸間隙、電漿頻率的巨大減少、磁性 材料的異常電磁響應，…等。結合奈米結構的超物質是一項新的研究領堿。它存在著很大的挑戰。如 何將理論的設計整合到實際的應用中，是一個亟待解決的課題。我們的挑戰，包括：(1)結構與特性 的關係和光譜響應的測定，特別是當超物質的基本構成物質是小到奈米尺寸的結構時(2)在可選用的 設計中，確認可以快速製造和標準化的設計，(3)測定控制效能(損耗)的因素。 最近半導體科技的發展使得製造人工半導體超物質成為可能。這些新的材料可以由非常小的奈米 結構所構成。奈米結構半導體超物質可以使其電磁響應的範圍落在可見光的區域。這對於實際的元件 應用有很大的好處。超物質的發展有趣但是困難的原因在於它本身位於物理與技術的十字路口。需要 兩者密切的搭配才能達成；最終的成功不僅需仰賴對於材料本身及其結構的全盤瞭解並且同時需要一 個結合奈米科技及當代最先進的特殊技術的科技。我們這裡所提出的計畫就是要抓住利用奈米結構所 建構的超物質的最關鍵議題。 我們提出的半導體超物質計畫，包羅各種學科的研究。這是一個理論學者、物理學家和技術工程 人員的共同研究計畫。我們的研究團隊，將不同領域、不同才能的人結合在一起，從不同的角度探討 問題的所在。這個計畫由四個分離但息息相關的部分所組成：(1)由奈米結構所成長與製造的超物質， (2)在微波和光學系統中，材料的特性和新穎的應用，(3)在低溫高磁環境下超物質的光學研究，(4) 崁入奈米物件系統之光學響應的理論研究。我們的計畫，建構在數個本世紀最重要的奈米、材料、及 光學技術之上。我們計畫中的一些重要的技術目標有： .. 演驛砷化銦、銻化銦和銻化鎵結構的量子點和量子環崁入到各式不同的主材料中。 .. 針對由半導體奈米物件所製成的人工超物質做多角化的研究。 .. 瞭解並控制半導體奈米物件結合於半導體奈米結構超物質系統之電、磁和磁光特性。 .. 對於由半導體奈米物件所製成之新的超物質發展包括量子和光學非局化效應的量化描述。 .. 發展並完成橢圓儀量測、直接的磁性量測和利用近場顯微鏡在低溫高磁系統中針對超物質的光學 研究。 .. 發展積體雷射和利用於慢速光元件的光子晶體結構。 .. 藉由半導體奈米結構研發可見光範圍之左手物質(left handed material)。 我們的研究團隊由在各自領域有豐富研究經驗的人員組成。主要成員來自交大，也有中興大學與 台大的教授參與。還有一位來自荷蘭Twenty University 的Prof. Wijers 參與，他是奈米結構中光學理論 的權威。我們這個團隊過去有密切的合作。目前每月均有固定的集會討論。理論上我們已經預測半導 體量子環有可能成為在可見光範圍的左手物質。藉由此計畫我們將嘗試在實驗上予以實現。 本計畫的實驗將得到交大奈米科技中心的全力支援。許多研究將在奈米科技中心的實驗室完成。 交大奈米科技中心已承諾在儀器的使用，新技術的開發以及人力與物力上全力的配合。它的 commitment 將是本計畫成功的一大關鍵。

The proposed program presented here targets one of the most exciting and challenging fields in nanotechnology – the collective behavior and functionality of materials with embedded artificial nano-objects. Metamaterials are a new class of artificially structured composite materials that display superior and unanticipated properties not observed readily in nature and in the constituent materials. Examples of such properties include negative refractive index and transmission gaps for electromagnetic and acoustic waves, colossal reductions in the plasmon frequencies, and magnetic responses in composites made out of nonmagnetic constituents, etc.. The aim of metamaterials development is to propose, fabricate and characterize novel configurations of available materials for achieving new media with desired properties. However, most of the designs are still in the stage of theoretical investigation and there is a big challenge to integrate them in real applications. Some of the challenges that lie ahead are: (1) determination of the structure-property relationships and spectral responses, particularly as the metamaterial building-block sizes shrink to the nanoscale, (2) identification of options for rapid fabrication and prototyping, and (3) determination of the factors that control the performance (losses). Recent technological progress in semiconductor technology made it possible to fabricate artificial semiconductor metamaterials. Those new materials can be constructed from very small objects, typically a few tens of nanometers in size. Unlike some the metamaterials that have been developed, nano-structured semiconductor metamaterials, because of the small size of the nano-objects, potentially can manipulate electromagnetic fields in the optical regime. This capability along with the semiconductor technoplogy will open up new applications and potentially have huge impact to the future optoelectronic device industry. The reason that metamaterials development is interesting but difficult is that it is at the cross road of physics and technology. Its eventual success is dependent upon our thorough understanding on material itself and at the same time a viable technology that combines the nanotechnology with state-of-the-art characterization techniques. The proposed program is designed to tackle the most critical issues of metamaterials built from nanostructures. Here we proposed a tightly coupled multidisciplinary investigation of metamaterials. This is a collaboration program among theoreticians and experimentalists, physicists and technologists. The combined and diverse talents of this team will enable us to tackle the problem from different angles. This project is made up of four separate but strongly related parts: (1) the growth and fabrication of metamaterials from nanostructures (2) material properties and novel applications in the areas of RF and optical systems (3) optical study of metamaterials at low temperature and high magnetic field environment (4) theoretical investigation of optical response of systems with embedded nano-objects. We propose a comprehensive research plan which builds at the intersection of several important nano, material and optical technologies of this century. We plan to investigate areas in which these technologies overlap to provide new functionality. Some key technical goals and operational features of our plan are: ‧ Demonstration of growth of InAs, InSb and GaSb quantum structures like quantum dots and quantum rings embedded in various kinds of host materials ‧ Perform a multilateral study of artificial metamaterials made from semiconductor nano-objects ‧ Understand and control electrical, magnetic and magneto-optical properties of systems of semiconductor nano-objects combined in semiconductor nano-structured metamaterials ‧ Develop quantitative description of new metamaterials built from semiconductor nano-objects including quantum and optical non-locality effects ‧ Perform and develop ellipsometry measurement, direct magnetism measurement and optical study with SNOM for the metamaterials in the cryogenic system ‧ Development of integrated QD laser and photonic crystal structure for slow light devices ‧ A team of researchers who have substantial research experience in their respective fields and have a demonstrated commitment to collaborative research ‧ Strong support and commitment from the Center of Nano Science and Technology at the National Chiao Tung University to support the research needs of this program