Wafer-Scale Ni Imprint Stamps for Porous Alumina Membranes Based on Interference Lithography (original) (raw)
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Aluminium pre-patterning for highly ordered nanoporous anodized alumina
Photonics and Nanostructures-fundamentals and Applications, 2007
A pre-patterning method of aluminium surface, in order to obtain highly ordered nanoporous anodized alumina on large areas is presented. Aluminium single crystals have been used as a substrate and a 2D hexagonally closed-packed lattice of shallow pits, with diameter of about 200 nm and period of 350 nm, has been successfully achieved by direct writing laser lithography (DWL) and wet etching. Finally, anodic oxidation of the single crystal at high cell voltage in phosphoric solution results in oxide growth with pore ordering superimposed by the pre-patterning procedure. #
Control of the Anodic Aluminum Oxide Barrier Layer Opening Process by Wet Chemical Etching
Langmuir, 2007
In this work, it has been shown that, through a highly controlled process, the chemical etching of the anodic aluminum oxide membrane barrier layer can be performed in such a way as to achieve nanometer-scale control of the pore opening. As the barrier layer is etched away, subtle differences revealed through AFM phase imaging in the alumina composition in the barrier layer give rise to a unique pattern of hexagonal walls surrounding each of the barrier layer domes. These nanostructures observed in both topography and phase images can be understood as differences in the oxalate anion contaminated alumina versus pure alumina. This information bears significant implication for catalysis, template synthesis, and chemical sensing applications. From the pore opening etching studies, the etching rate of the barrier layer (1.3 nm/min) is higher than that of the inner cell wall (0.93 nm/min), both of which are higher than the etching rate of pure alumina layer (0.5-0.17 nm/min). The established etching rates together with the etching temperature allow one to control the pore diameter systematically from 10 to 95 nm.
Direct nanoimprint lithography of Al2O3 using a chelated monomer-based precursor
Nanostructuring of Al 2 O 3 is predominantly achieved by the anodization of aluminum film and is limited to obtaining porous anodized aluminum oxide (AAO). One of the main restrictions in developing approaches for direct fabrication of various types of Al 2 O 3 patterns, such as lines, pillars, holes, etc, is the lack of a processable aluminum-containing resist. In this paper, we demonstrate a stable precursor prepared by reacting aluminum tri-sec-butoxide with 2-(methacryloyloxy)ethyl acetoacetate, a chelating monomer, which can be used for large area direct nanoimprint lithography of Al 2 O 3 . Chelation in the precursor makes it stable against hydrolysis whilst the presence of a reactive methacrylate group renders it polymerizable. The precursor was mixed with a cross-linker and their in situ thermal free-radical co-polymerization during nanoimprinting rigidly shaped the patterns, trapped the metal atoms, reduced the surface energy and strengthened the structures, thereby giving a ∼100% yield after demolding. The imprinted structures were heat-treated, leading to the loss of organics and their subsequent shrinkage. Amorphous Al 2 O 3 patterns with line-widths as small as 17 nm were obtained. Our process utilizes the advantages of sol-gel and methacrylate routes for imprinting and at the same time alleviates the disadvantages associated with both these methods. With these benefits, the chelating monomer route may be the harbinger of the universal scheme for direct nanoimprinting of metal oxides.
The controlled fabrication of highly ordered anodic aluminium oxide (AAO) templates of unprecedented pore uniformity directly on Si, enabled by new advances on two fronts -direct and timed anodisation of a high-purity Al film of unprecedented thickness (50 mm) on Si, and anodising a thin but pre-textured Al film on Si, has been reported. To deposit high-quality and ultrathick Al on a non-compliant substrate, a prerequisite for obtaining highly ordered pore arrays on Si by self-organisation while retaining a good adhesion, a specially designed process of e-beam evaporation followed by in situ annealing has been deployed. To obtain an AAO template with the same high degree of ordering and uniformity but from a thin Al film, which is not achievable by the selforganisation alone, pre-patterning of the thin Al surface by reactive ion etching using a freestanding AAO mask that was formed in a separate process was performed. The resultant AAO/ Si template provides a good platform for integrated growth of nanotube, nanowire or nanodot arrays on Si. Template-assisted growth of carbon nanotubes (CNTs) directly on Si was demonstrated via a chemical vapour deposition method. By controllably removing the AAO barrier layer at the bottom of the pores and partially etching back the AAO top surface, new CNT/Si structures were obtained with potential applications in field emitters, sensors, oscillators and photodetectors.
Roll-to-Roll Anodization and Etching of Aluminum Foils for High-Throughput Surface Nanotexturing
Nano Letters, 2011
b S Supporting Information S urface nanotexturing tailors the physical and chemical properties of materials, and has been actively utilized in the past for enabling new functionalities. Selected examples include, antireflective substrates for high-efficiency solar cells, 1,2 superhydrophobic surfaces for self-cleaning materials, 3,4 engineered layers for enhanced or inhibited biofilm formation, 5 low friction surfaces for mechanical systems, 6 and synthetic gecko adhesives. In this regard, large-scale (>m 2 ) production of textured surfaces with optimal micro/nano scale features for a given application is of profound interest, especially for hard substrates such as metals and ceramics. Here, we present roll-to-roll (R2R) anodization and etching of aluminum foils for high-throughput, low-cost nanotexturing of surfaces with tunable topography, and feature size and density. The optical and surface wetting properties of the textured foils were systematically characterized, demonstrating the utility of this technique for enabling substrates with user-defined, functional performance. In addition, R2R textured pores and bowls were used as zeptoliter reaction vessels for the wellcontrolled synthesis of nanoscale inorganic, organic, and plasmonic materials, demonstrating yet another powerful potential use of the presented platform.
Self-organized porous-alumina implantation masks for generating nanoscale arrays
2003
Starting from two-step anodizing recipes available in the literature, we fabricated self-supporting ordered ion-implantation masks that are several mm2 in area and approximately 2 μm thick. SEM micrographs reveal self-organized structures with straight open pores, 50–150 nm in diameter, extending completely through the mask. As reported previously, the pore diameter and spacing depend critically upon the anodization parameters, eg type of acid and its molality, the applied voltage and the solution temperature.
2012
I hereby declare that the thesis becomes the property of Universiti Malaysia Perlis (UniMAP) and to be placed at the library of UniMAP. This thesis is classified as : CONFIDENTIAL (Contains confidential information under the Official Secret Act 1972)* RESTRICTED (Contains restricted information as specified by the organization where research was done)* OPEN ACCESS I agree that my thesis is to be made immediately available as hard copy or on-line open access (full text) I, the author, give permission to the UniMAP to reproduce this thesis in whole or in part for the purpose of research or academic exchange only (except during a period of _____ years, if so requested above).