Templated Self-Assembly of Nanoporous Alumina: Pore Formation and Ordering Mechanisms, Methodologies, and Applications by Ramkumar Krishnan M.S., Chemical Engineering, University of Florida, USA (1999) B.Tech., Chemical and Electrochemical Engineering, CECRI, India (1996) Submitted to the Department of Materials Science and Engineering in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY September 2005 © Massachusetts Institute of Technology 2005. All rights reserved. Author ' . Department of Materials Science and Engineering August 18, 2005 Certified b'y ~ ,;-;-; ;.H •• • •••••••••••••• l ':"':':":" . , Carl V. Thompson Stavros Salapatas Professor of Materials Science and Engineering Thesis Advisor Accepted by (:;;7=:":' • :.:.: :.:.=.o .,::.: ::!!:.:,.::.: :; ; ~-er-b-ra":n:::d ~ccxi::iiiieliirr ~~~~~~t\ P. Simmons Professor of Materials Science and Engineering MASSACHUSETTS INS OF TECHNOLOGY Chair, Departmental Committee on Graduate Students [ SE~ 29 2005 LIBRARIES [...]... Cross-section SEM images of ordered porous alumina with 200nm pore spacing formed in a) 5wt% phosphoric acid b) 0.15M oxalic acid The thickness of porous alumina is higher in the case of oxalic acid 165 6-8 Effect of the wavelength of a perturbation on its growth rate For templated self-assembly, voltages that correspond to the fastest growing wavelength equal to D1 and D2 still lead to self-assembly with... fixed at the lithography period 6-9 Effect of temp1ating on the ordering of porous alumina Without templating, disordered pores form at all voltages and pH as the aluminum 18 film is thin With templating, ordered porous alumina with controlled diameter and spacing is achieved 6-10 171 Templated self-assembly of porous alumina by direct patterning of the surfaces of aluminum films on silicon substrates... Effect of concentration of the phosphoric acid on a) the barrier oxide thickness b) the pore diameter and c) the volume expansion factor of porous alumina with hexagonally ordered pores and with pore spacings of 200nm 176 6-14 Effect of concentration of oxalic acid on the a) barrier oxide thickness and b) pore diameter of ordered porous alumina with 200nm pore spacing 178 6-15 Schematic of. .. Dependence of the stress on the applied current density and concentration of oxalic acid 5-7 148 Dependence of the stress on the applied current density and concentration of sulfuric acid 5-8 142 148 Log-log plot of the pore spacing vs the stress The slope of the curve gives the value of the exponent of the power law and is shown in the figure 5-9 149 Plot showing the validity of Asaro-Tiller... characteristics of CNTs grown on (a) flat substrates (b) ordered porous alumina templates The tum-on electric field in the case of CNTs in ordered porous alumina template is 50% lower than in the case of CNTs grown on flat substrates due to screening effect (Measurements by Hung Nguyen) 243 27 10-11 Schematic of the bottom-up assembly of nanostructures using porous alumina nano-breadboard (Picture by Prof Carl... alumina C-4 286 SEM image of gold nanowires grown inside the porous alumina by reduction of hydrogen chloroaurate Porous alumina was partially removed by KOH etching for imaging the nanowires C-5 286 Cobalt tubes embedded in a self-ordered porous alumina template with a interpore distance of 500 nm and a pore diameter of 300 nm are shown in (a) to (c) (a) Top-view image of an array of Cobalt/PLLA composite... images of porous alumina formed in a) 0.3M oxalic acid at 40V after 2nd anodization b) O.3M sulfuric acid at 25V after 2nd anodization 13 101 3-6 (a) AFM image of the barrier oxide on the backside of alumina (top left) (b) The plot (top right) shows the periodic humps and valleys on the backside of alumina (c) A 3-D rendition is also shown in the figure on the 103 bottom left comer 3-7 SEM images of double... Dewetting of 200 A nickel film on flat Si02 substrates The average resulting particle size is 200-250nm.(SEM imaging by R.Tadepalli) 11-3 251 253 Dewetting of 200A nickel film on the front-side of porous alumina templates (with open pores) Porous alumina templates with pore diameter (a) 35nm (b) 160nm.(SEM imaging by R.Tadepalli) 253 11-4 Dewetting of 200A nickel film on the back-side of porous alumina. .. The number of rows of pores decreases with increasing voltage 193 7-6 SEM images of AAO formed by anodizing aluminum masked by oxide lines with spacings of 400nm and widths of - 200nm Anodization was performed in 5wt% phosphoric acid at the voltages indicated in the figures The number of rows of pores across the width of the grating decreases with increasing voltage 7-7 SEM images of AAO fonned by anodizing... (barrier-type film growth) of the anodic oxidation of aluminum: a) sulfuric acid; b) oxalic acid; c) phosphoric acid 4-6 Dependence of the current efficiency for aluminum oxidation process on the current density, pH and electrolyte 4-7 120 Dependence of electric field at the barrier layer of the aluminum oxide on the current density, pH and electrolyte 4-8 119 120 SEM images of porous alumina formed by oxidation . Summary 153 6. Templated self-assembly: Long-range ordered porous alumina 155 6.1 Introduction 155 6.2 Templated self-assembly of porous alumina: Phenomenology 157 6.3 Experimental. porous alumina with controlled diameter and spacing is achieved. 171 6-10 Templated self-assembly of porous alumina by direct patterning of the surfaces of aluminum