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Electrochemical Etching (electrochemical + etching)

Distribution by Scientific Domains
Physics and Astronomy66%

Selected Abstracts

Selective Electrochemical Etching of Single-Walled Carbon Nanotubes

ADVANCED FUNCTIONAL MATERIALS, Issue 22 2009
Dacheng Wei
Abstract Single-walled carbon nanotubes (SWNTs) are a promising material for future nanotechnology. However, their applications are still limited in success because of the co-existence of metallic SWNTs and semiconducting SWNTs produced samples. Here, electrochemical etching, which shows both diameter and electrical selectivity, is demonstrated to remove SWNTs. With the aid of a back-gate electric field, selective removal of metallic SWNTs is realized, resulting in high-performance SWNT field-effect transistors with pure semiconducting SWNT channels. Moreover, electrochemical etching is realized on a selective area. These findings would be valuable for research and the application of SWNTs in electrochemistry and in electronic devices. [source]

Mesoporous GaAs double layers for layer transfer processes

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2009
Enrique Garralaga Rojas
Abstract Mesoporous GaAs double layers with different porosities and thicknesses up to 7,µm are formed on highly doped p-type 4,inch GaAs substrates by means of electrochemical etching in highly concentrated hydrofluoric acid electrolytes. Small ,111, oriented pyramids form at the interface between porous layer and substrate if etching current densities below 7.5,mA,cm,2 are applied. Porous double layers with different porosities are obtained by varying simultaneously the etching current density and the electrolyte concentration. The porosity of the porous GaAs layers decreases nearly linearly from 69 to 53% with electrolyte concentrations increasing from 30 to 50,wt.%, respectively. The etching process increases the mean roughness of the porous layer surface from 0.15 to 0.24,nm. [source]

Luminescence and vibrational properties of erbium-implanted nanoporous GaN

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008
C. B. Soh
Abstract Implantation of erbium (Er) into GaN is useful in creating selected areas to emit at the green, yellow and infrared wavelengths. Enhanced erbium activation is obtained when erbium is implanted into porous GaN formed by electrochemical etching than into as-grown GaN. This is due to the increase in surface areas for light extraction and the availability of more free surfaces to accommodate strain when it is annealed. Furnace annealing at 1100 °C for 30 mins in nitrogen gives rise to higher band-edge photoluminescence intensity. Apart from the host GaN phonon modes, we have also observed disorder-induced lattice vibrations at 170, 200 and 350-365 cm,1 from Er-implanted porous GaN. The E2 (high) mode of GaN also shifts towards higher energy at higher annealing temperatures, indicative of more erbium occupying the VGa site (ionic radii of Er > Ga) and hence increasing the compressive stress in the GaN crystal lattice. The prominent defect-induced local vibrational modes in Er-doped nanoporous GaN are also observed in ultraviolet resonant Raman scattering. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Influence of iodine molecule adsorption on electronic properties of porous silicon studied by FTIR and EPR spectroscopy

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2007
L. A. Osminkina
Abstract The infrared absorption and electron paramagnetic resonance spectroscopy are used for studying the effect of adsorption of iodine (I2) molecules, strong acceptors of electrons, on the electronic properties of silicon nanocrystals in micro- and mesoporous silicon layers with different types of doping impurities. It is found that the concentration of free charge carries (holes) in silicon nanocrystals, obtained by electrochemical etching of p-type and n-type silicon wafers, sharply increases in the presence of I2 molecules. At the same time the decrease of the dangling silicon bonds (Pb -centers) concentration is observed. A microscopic model proposed for explaining this effects presumes the formation of donor-acceptor pairs (Pb1+ -I2,), and shallow acceptor states on the porous silicon surface which, together with the initial dopant and surface defect states, specify the charge carrier type and concentration in the silicon nanocrystals. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Porous silicon surfaces for metabonomics: Detection and identification of nucleotides without matrix interference

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2007
D. Gómez
Abstract In present work, porous silicon surfaces (PSS) have been developed for time of flight mass spectrometric experiments (TOF-MS) in the monitoring of nucleotides, commonly found as metabolites in the cell. The mass range of the studied molecules (, 400 amu) is common to several important messengers and other metabolites. Different porosified surfaces have been developed by means of electrochemical etching and different degree of porosity and pore size achieved as function of silicon dopant concentration, silicon resistivity, current density and the presence or absence of illumination along the process. As main conclusion, it can be said that an interesting commercial nucleotide (Cyclic adenosine monophosphate, c-AMP) has been detected on low concentrations (,hundreds of femtomols) for some of the fabricated porous surfaces. Taking into account that these concentrations are similar to the ones found in real samples, this result opens the possibility to the fabrication of DIOS (Desorption Ionization On Silicon) chips for the detection of nucleotides in biological fluids. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]