A review on highly ordered, vertically oriented TiO2 nanotube arrays: Fabrication, material properties, and solar energy applications

The worldwide thirst for portable consumer electronics in the 1990s had an enormous impact on portable power. Lithium ion batteries, in which lithium ions shuttle between an insertion cathode (e.g., LiCoO2) and an insertion anode (e.g., carbon), emerged as the power source of choice for the highperformance rechargeable-battery market. The performance advantages were so significant that lithium ion batteries not only replaced Ni-Cd batteries but left the purported successor technology, nickel-metal hydride, in its wake.1 The thick metal plates of * To whom correspondence should be addressed. J.W.L: e-mail, jwlong@ccs.nrl.navy.mil; telephone, (+1)202-404-8697. B.D.: e-mail, bdunn@ucla.edu; telephone, (+1)310-825-1519. D.R.R.: e-mail, rolison@nrl.navy.mil; telephone, (+1)202-767-3617. H.S.W.: e-mail, white@chem.utah.edu; telephone, (+1)810-585-6256. † Naval Research Laboratory. ‡ UCLA. § University of Utah. 4463 Chem. Rev. 2004, 104, 4463−4492

Three-dimensional battery architectures.

In this study highly ordered titania nanotube arrays of variable wall thickness are used to photocleave water under ultraviolet irradiation. We demonstrate that the wall thickness and length of the nanotubes can be controlled via anodization bath temperature. We find that the nanotube wall thickness is a key parameter influencing the magnitude of the photoanodic response and the overall efficiency of the water-splitting reaction. For 22 nm inner pore diameter nanotube arrays, those fabricated in a 5 °C anodization bath, 224 nm length and 34 nm wall thickness produced a photoanodic response that was thrice that of a nanotube array fabricated in a 50 °C anodization bath, 120 nm length and 9 nm wall-thickness. At high anodic polarization, above 1 V, the quantum efficiency under 337 nm illumination was greater than 90%. For the 5 °C anodization bath samples (22 nm pore-diameter, 34 nm wall thickness), upon 320−400 nm illumination at an intensity of 100 mW/cm2, hydrogen gas was generated at the power−time norm...

Enhanced Photocleavage of Water Using Titania Nanotube Arrays

Described is the fabrication of self-aligned highly ordered TiO2 nanotube arrays by potentiostatic anodization of Ti foil having lengths up to 134 μm, representing well over an order of magnitude i...

Anodic Growth of Highly Ordered TiO2 Nanotube Arrays to 134 μm in Length

and Perspectives Sophie Carenco,†,‡,§,∥,⊥ David Portehault,*,†,‡,§ Ced́ric Boissier̀e,†,‡,§ Nicolas Meźailles, and Cleḿent Sanchez*,†,‡,§ †Chimie de la Matier̀e Condenseé de Paris, UPMC Univ Paris 06, UMR 7574, Colleg̀e de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France ‡Chimie de la Matier̀e Condenseé de Paris, CNRS, UMR 77574, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Chimie de la Matier̀e Condenseé de Paris, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Laboratory Heteroelements and Coordination, Chemistry Department, Ecole Polytechnique, CNRS-UMR 7653, Palaiseau, France

Nanoscaled metal borides and phosphides: recent developments and perspectives

Two different morphologies of porous layers were observed in (100)-oriented n-InP anodically etched in an aqueous solution of HCl At high current density (60 mA/cm2) anodization leads to the formation of so-called current-line oriented pores When the current density decreased to values lower than 5 mA/cm2 the morphology of the porous layers sharply changed and the pores began to grow along definite crystallographic directions © 2000 The Electrochemical Society S1099-0062(00)06-078-8 All rights reserved

http://www.tf.uni-kiel.de/matwis/amat/publications/in_p/inp_final_revised.pdf

Formation of Porous Layers with Different Morphologies during Anodic Etching of n ‐ InP

Subjecting illuminated n-type silicon wafers to anodic bias in an HF containing electrolyte results in the formation of macropo res under certain conditions. In this paper the formation of randomly nucleated macropores is studied as a function of the applied potential, the temperature, and the doping levels of the samples. A large number of micrographs was evaluated by computerized image processing and the data obtained are compared to predictions of pore formation models. It was found that the formation of randomly nucleated macropores involves a prolonged nucleation phase. Starting from a polished surface, first macropores occur after a certain amount of Si has been homogeneously dissolved. In this nucleation phase the thickness of the homogeneously dissolved Si depends strongly on the doping level and the temperature, but only weakly on the applied bias. In a second phase of st able pore growth, the density of pores is investigated as a function of temperature and anodic potential. For low-doped material a strong influence of the space-charge region on the average macropore density is observed in accordance with existing models; an increased anodic bias, e.g., decreases the density of pores. For highly doped silicon the situation reverses; increasing anodic bias increases the pore density, in contrast to predictions. The pore growth in this region is not very sensitive to the space-charge region but seems to be dominated by the chemical-transfer rate. © 2000 The Electrochemical Society. S0013-4651(99)06-155-8. All rights reserved.

Dependence of Macropore Formation in n‐Si on Potential, Temperature, and Doping

Voltage oscillations were observed during anodic etching of 100 -oriented n-InP substrates in an aqueous solution of HCl at high constant current density. Under certain conditions, the oscillations lead to a synchronous modulation of the diameters of pores on large areas of the samples which indicates a correlation between the phases of the oscillations in the pores. These self-induced diameter oscillations may be useful for three-dimensional microstructuring of n-InP and thus for the design and fabrication of new photonic materials. © 2001 The Electrochemical Society. DOI: 10.1149/1.1370417 All rights reserved.

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Self-Induced Voltage Oscillations during Anodic Etching of n-InP and Possible Applications for Three-Dimensional Microstructures

The dependence of macropore formation in n-silicon on substrate orientation was investigated. Samples were cut from a large Si crystals in various orientations between {100} and {111}. Macropores were obtained by electrochemical etching in diluted HF following standard techniques. The growth direction of the macropores was found to be and , with a switch over at a critical angle of about 43, whereas "breakthrough" pores obtained without illumination at large field strength always grow in . The results can be partially understood by postulating different pore growth speeds for and , but indicate that a detailed understanding of pore growth in Si is still elusive. Introduction Porous Silicon, produced by anodic dissolution of Si in suitable electrolytes, has received much attention since the discovery of quantum wire effects and strong photoluminescence (PL) in one particular kind of porous Silicon (nanoporous Si) in 1989 . A large body of work was dedicated to the detailed mechanism of the PL and to the production of stable light emitting devices from porous Si so far without totally

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Crystal Orientation Dependence of Macropore Growth in n‐Type Silicon

The aim of this work is to explain the influence of the solvent molecules on silicon dissolution using several hydrofluoric acid containing organic electrolytes. The investigations focus on the morphology of the mesopores and macropores and the electrochemical valence of the overall reaction. Some basic properties of the electrolyte (polarity, tendency to form silicon oxide, and the H donor properties) were found to dominate the macropore formation in p-type silicon. For macropore formation the correct balance between the two main dissolution paths (direct silicon dissolution and dissolution via an anodic oxide) is very important. For mesopores in highly doped p- and n-type silicon the direct dissolution is dominant. The consequences of mixing organic and aqueous solutions are discussed.

/pdf/organic-and-aqueous-electrolytes-used-for-etching-macro-and-grmavejle5.pdf

J. Carstensen

Papers

Formation of Porous Layers with Different Morphologies during Anodic Etching of n ‐ InP

Dependence of Macropore Formation in n‐Si on Potential, Temperature, and Doping

Self-Induced Voltage Oscillations during Anodic Etching of n-InP and Possible Applications for Three-Dimensional Microstructures

Crystal Orientation Dependence of Macropore Growth in n‐Type Silicon

Organic and aqueous electrolytes used for etching macro- and mesoporous silicon