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

The morphology of porous layers obtained by electrochemical etching of (100) oriented n-GaAs substrates in an aqueous solution of HCl was studied. At low anodic current densities, up to 5 mA/cm 2 , pores in the form of triangular prisms grew along (111) crystallographic directions. For larger current densities the shape of the pores did not suffer any changes at the beginning of the process, while after a definite period of time the morphology of pores changed drastically to chains of tetrahedral voids with {111} facets.

http://esl.ecsdl.org/content/5/1/C14.full.pdf

Formation of Tetrahedron-Like Pores during Anodic Etching of (100) Oriented n-GaAs

61.43.Gt, 68.37.Hk, 81.65.Cf, 82.45.Vp Nucleation and growth of electrochemically obtained pores on (111) and (100) oriented n-Ge in different electrolytes was investigated. On rough surfaces pore density increases as the current density increases, whereas on smooth surfaces the situation is inverse, i.e., the pore density increases as the current density decreases. The macropores show strong anisotropic features with a cone-like shape. This can be under-stood if the passivation of the pore walls in Ge is less pronounced as in the case of Si or III–V com-pounds, but strongly anisotropic.

Electrochemical pore etching in Ge

Electrochemical etching of semiconductors, apart from many technical applications, provides an interesting experimental setup for self-organized structure formation capable, e.g., of regular, diameter-modulated, and branching pores. The underlying dynamical processes governing current transfer and structure formation are described by the current burst model: all dissolution processes are assumed to occur inhomogeneously in time and space as a current burst (CB); the properties and interactions between CBs are described by a number of material- and chemistry-dependent ingredients, like passivation and aging of surfaces in different crystallographic orientations, giving a qualitative understanding of resulting pore morphologies. These morphologies cannot be influenced only by the current, by chemical, material and other etching conditions, but also by an open-loop control, triggering the time scale given by the oxide dissolution time. With this method, under conditions where only branching pores occur, the ...

/pdf/self-organized-pore-formation-and-open-loop-control-in-wn4zc86yzt.pdf

Self-organized pore formation and open-loop control in semiconductor etching

New Insights into Si Electrochemistry and Pore Growth by Transient Measurements and Impedance Spectroscopy

Porous silicon layers etched through openings in an inert masking layer have potential applications for producing microstructures in silicon In order to overcome the isotropic nature of the porous silicon formation process around the mask edges, optimized organic electrolytes for etching macropores on p-type silicon were employed New kind of pores (dubbed “trenches”) were found, which are sensitive to mechanical stress and may prove useful for microstructuring silicon Systematic experiments are presented which investigate the stability, the crystal orientation dependence, and limitations of trench formation

http://www.tf.uni-kiel.de/matwis/amat/publications/electro_chem_trench/electro_chem_trench_revised_version.pdf

J. Carstensen

Papers

Formation of Tetrahedron-Like Pores during Anodic Etching of (100) Oriented n-GaAs

Electrochemical pore etching in Ge

Self-organized pore formation and open-loop control in semiconductor etching

New Insights into Si Electrochemistry and Pore Growth by Transient Measurements and Impedance Spectroscopy

Deep electrochemical trench etching with organic hydrofluoric electrolytes