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Title: Nanostructure array fabricated via ordered template
Other Titles: You xu mo ban fu zhu he cheng na mi jie gou zhen lie
Authors: Mei, Yongfeng (梅永豐)
Department: Dept. of Physics and Materials Science
Degree: Doctor of Philosophy
Issue Date: 2005
Publisher: City University of Hong Kong
Subjects: Nanostructures
Notes: CityU Call Number: QC176.8.N35 M44 2005
Includes bibliographical references.
Thesis (Ph.D.)--City University of Hong Kong, 2005
xiv, 197 leaves : ill. (some col.) ; 30 cm.
Type: Thesis
Abstract: This work aims at preparing and characterizing two-dimensional (2D) nanostructure arrays. The methodology is the template-assistant growth of nanostructures of several different materials. Self-assembled porous anodic alumina (PAA) and PAA on Sisubstrate (PAA-Si) are applied as template for growing nanostructures and endow them with homogeneous distribution order. Different materials are embedded into the pores of the template so as to form nanostructures. Their physical properties are investigated using various techniques. The work serves for the development of nano-devices and belongs to the field of Si nano-integration, although it is still preliminary. This work addresses the problems shown as follows: dense nanostructures in large area, their characteristics and functions, and homogeneous distribution. Some insight into the growth techniques of nanomaterials is provided. Electrochemical method is used to fabricate PAA and PAA-Si. With the control of growth parameters such as electrolytes and applied voltage, PAA are produced with highly ordered nano-pores of different size. The observed nano-wires and nano-tubes of alumina in the PAA fabrication are also discussed. PAA-Si provides the possibility of nano-structure compatible to the mature Si-technology. Their growth is monitored by the I-t curve, and investigated by their photoluminescence (PL) and atomic force microscopy (AFM), which is affected by the contrast of the electric field across the barrier layer. PAA and PAA-Si are successfully fabricated and fundamental understanding on their growth process is obtained. With the assistance of PAA and PAA-Si template respectively, polycrystalline Si and SiO2 nano-islands of various size and pattern are prepared. On the contrary, the SiO2 nano-islands affect the optical properties of PAA-Si, which shows its growth process. It is tried to embed Cu into the pores of the PAA-Si template, i.e. onto the SiO2 islands, which results in copper oxide, mainly Cu2O, nano-wires on SiO2 islands. The connection is confirmed by transmission electron microscope (TEM). Cathodoluminescence (CL) helps for clarifying the influence factors of Cu2O growth, which could be useful for other semiconductor oxide nanomaterials. Carbon is embedded into the pores above SiO2 to form a novel nano-MOS array. Metallic carbon nanostructures are in the insulated alumina nano-channels and connect the nano-SiO2 islands. The overall behaviors of the nano-MOS array are investigated through its I-V and frequency-dependent C-V characteristics. The method of saturated vapor adsorption (SVA) is contrived to prepare nanorods, nanotubes etc. Ge nanorods on both PAA and PAA-Si and their array are produced. Laser Raman scattering and PL are used to characterize them, showing quantum confinement effect. Ge tube structures of similar size to nanorods in the pores of template are also discovered, which have different mechanisms from nanorods. Besides Si substrate, functional film may also serve as the substrate of nanostructures. ZnO film is fabricated using the technique of plasma immersion ion implantation and deposition (PIII&D). It is tried to achieve p-type ZnO by nitrogen doping but not succeeded. Some preliminary results are obtained for ZnO nanorods on PAA, ZnO nanowires on ZnO film, and ZnO nanorods on N-doped ZnO film. This work explores the fabrication of nanostructures arrays of various materials and their characterization. It will contribute to the development of nano-electronics and nanooptoelectronics.
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