一維及零維奈米電子學之物理與元件( I )

Abstract

本計畫擬探討一維奈米線與零維奈米顆粒的前瞻基礎物性，包括金屬奈米線的量子（電荷與自旋）傳輸特性、半導體奈米線的導電機制與雜質能級、奈米接點的特性，及奈米顆粒與量子點的新穎電學性質，將著重在深入與前沿的基礎物性研究，並且探求元件原型之製作與物理解釋。 研究主題包括：（1）擬探討金屬奈米線（如RuO2, ITO, TiSi）之量子干涉傳輸特性（弱局域效應、普適電導漲落、1/f 噪音等），理解電子散射機制、自旋相干長度，並發現新科學。電子—聲子散射主宰奈米電子元件之冷卻，普適電導漲落反映奈米元件中的動態結構缺陷性質。（2）擬探討（掺雜）ZnO奈米線的導電機制與雜質能級，並擴展到其他半導體奈米線的研究。（3）擬進行金屬奈米線與次微米金屬電極介面處之奈米接點的定量表徵與物理解釋。（4）擬進行超導體奈米線，和超導體電極/金屬奈米線複合結構的研究。（5）擬研究零維奈米顆粒和量子點的新穎傳輸性質。 本計畫強調定量與系統性的量測，深入的數據分析，與理論的密切合作，並追求研究成果在國際上的高度能見度與影響力。本計畫的主軸是進行深入尖端的電子（電荷與自旋）傳輸研究，以期一方面發現奈米尺度新科學，另一方面奠立奈米電子元件的應用基礎。

In this Project, we propose to investigate the fundamental physical properties of one-dimensional nanowires and zero-dimensional granular structures and semiconductor quantum dots, including the quantum (both charge and spin) transport properties of metal nanowires, intrinsic charge conduction processes in semiconductor nanowires, quantitative characterizations of single nanocontacts, superconducting nanowires and nanoscale superconductor/normal-metal heterostructures, as well as electronic properties of granular structures and quantum dots. We propose to study in-depth the following fundamental topics in nanoscience. (1) Quantum-interference transport in metallic (RuO2, ITO, TiSi, etc.) nanowires, to learn about the weak-localization effect, Aharonov-Bohm-like oscillations, universal conductance fluctuations, and 1/f noise, etc. The electron dephasing (decoherence) time and electron spin (spin-orbit and spin-flip) scattering time can be extracted through these measurements. The electron-phonon relaxation time, which will be crucial for the cooling capability in nanoelectronic devices, will be measured. Universal conductance fluctuations (including 1/f noise and random telegraph noises) studies shall allow us to probe the low-temperature properties of dynamical structural defects, which often exist in great amounts, in nanostructures. (2) Four-probe electrical measurements on individual nanowire devices over a wide temperature interval and in magnetic field, to unravel the electrical conduction mechanisms and the (shallow) impurity levels of natively and intentionally doped ZnO nanowires. Electron-phonon relaxation time in degenerately doped semiconductor nanowires will also be investigated. (3) Measurements of electrical properties of single nanocontacts formed at interfaces between metallic nanowires and submicron electrodes, to clarify the conduction processes through nanoconstrictions. In addition, artificial nanocontacts will be fabricated by electron-beam lithograph in a controlled manner and studied. (4) Measurements of superconducting nanowires and superconductor/normal-metal nanowire heterostructures, to explore novel superconducting phenomena at the nanoscale. (5) Measurements of electronic properties of granular structures around the quantum percolation threshold as well as the spin-dependent transport through semiconductor quantum dots, to develop concepts of zero-dimensional physics. In brief, we propose in this Project to focus on very quantitative and systematic measurements of individual metal, semiconductor, and superconductor nanowires, as well as on in-depth analyses and explanation of the data. Close collaborations between experiment and theory will be stressed. The goals of this Project are to achieve the highest possible research standard on the quantum (both charge and spin) transport studies of individual nanowires, to discover new science at the nanoscale, and to pave the way for the future implementation of nanoelectronic devices. This research tem aims to exercise itself to become one of the most prestigious research teams on the electronic properties of nanostructures in the international nanoscience and nanotechnology communities. Close and fruitful international collaborations with the Low Temperature Physics Laboratory of RIKEN, Japan, and the Physics Department of Hong Kong University of Science and Technology will be fostered in this Project.