Silicon quantum wire array fabrication by electrochemical and chemical dissolution of wafers
TL;DR: In this paper, free standing Si quantum wires can be fabricated without the use of epitaxial deposition or lithography using electrochemical and chemical dissolution steps to define networks of isolated wires out of bulk wafers.
Abstract: Indirect evidence is presented that free‐standing Si quantum wires can be fabricated without the use of epitaxial deposition or lithography. The novel approach uses electrochemical and chemical dissolution steps to define networks of isolated wires out of bulk wafers. Mesoporous Si layers of high porosity exhibit visible (red) photoluminescence at room temperature, observable with the naked eye under <1 mW unfocused (<0.1 W cm−2) green or blue laser line excitation. This is attributed to dramatic two‐dimensional quantum size effects which can produce emission far above the band gap of bulk crystalline Si.
Citations
More filters
TL;DR: The use of quantum dots (QDs) in the development of fluorescence based sensors has increased over the past decade because of the unique properties of these materials as mentioned in this paper, however, most demonstrated sensors have been developed based upon cadmium containing QDs that can be toxic.
Abstract: Using quantum dots (QDs) in the development of fluorescence based sensors has increased over the past decade because of the unique properties of these materials. However, most demonstrated sensors have been developed based upon cadmium containing QDs that can be toxic. Alternative QD materials that have been gaining attention for sensor development are silicon nanocrystals (SiNCs); they are non-toxic and abundant, and their properties are tailorable. This review outlines the general sensing mechanisms employed for the development of QD based sensors, examples of developed SiNC sensors, and will finally conclude with future prospects of using SiNCs as sensors.
54 citations
TL;DR: In this article, the effects of strain-induced band splitting and band warping on the modification of the average conductivity effective mass and carrier scattering rates were evaluated using a classification scheme based on carrier confinement type (electrostatic and spatial) and the degrees of freedom of the mobile carriers.
Abstract: Using a classification scheme based on carrier confinement type (electrostatic and spatial) and the degrees of freedom of the mobile carriers (3DOF, 2DOF, and 1DOF), strain effects on 3DOF to 1DOF silicon logic devices are compared from quantum confinement and device geometry perspectives. For these varied device geometries and types, the effects of strain-induced band splitting and band warping on the modification of the average conductivity effective mass and carrier scattering rates are evaluated. It is shown that the beneficial effects of strain-induced band splitting are the most effective for devices with little or no initial band splitting and become less so for devices with already large built-in band splitting. For these devices with large splitting energy, the potential for strain-induced carrier conductivity mass reduction through repopulation of lower energy bands and the suppression of optical intervalley phonon scattering are limited. On the other hand, for all devices without spatial confin...
54 citations
TL;DR: In this paper, the authors demonstrate a new way of making low-cost miniature fuel cells for portable applications based on proton conducting porous silicon membranes, which consists in the chemical grafting of silane molecules containing ionizable groups on the pores walls to mimic the structure of ionomer such as Nafion ®, usually used to ensure the proton conductivity of PEM fuel cells.
53 citations
TL;DR: In this article, an immersion plating of nickel (Ni) on a porous silicon (PS) layer has been investigated in concentrated ammonium fluoride and dilute hydrofluoric acid (HF) solutions containing when the PS sample was exposed to the bath containing 5 M and 50 mM at pH 8, metallic Ni was clearly observed at the open circuit potential without using a reducing agent or any activation treatment at room temperature.
Abstract: Immersion plating of nickel (Ni) on a porous silicon (PS) layer has been investigated in concentrated ammonium fluoride and dilute hydrofluoric acid (HF) solutions containing When the PS sample was exposed to the bath containing 5 M and 50 mM at pH 8, metallic Ni was clearly observed at the open-circuit potential without using a reducing agent or any activation treatment at room temperature. However, no deposition was detected when the sample was immersed in a 0.5 wt % HF solution containing the same concentration of at pH 2. The different deposition behavior is discussed on the basis of mixed potential theory, changes in the stability of Si-H bonds of PS as indicated in the Fourier transform infrared spectra, and the different state of Ni complex formation as obtained from the UV-vis spectra. The position of the Ni redox levels in both solutions with respect to the bandedges of Si was also determined and the results revealed a nearly similar energetic situation. Results from current-potential curves showed that a slow Ni deposition from the alkaline solution occurred in the dark and different possible reaction mechanisms were proposed. They also revealed the enhancement of the deposition under illumination, indicating that the deposition mechanism is electron transfer from the conduction band. X-ray photoelectron spectroscopy detected no silicon oxides on the PS surface after being immersed in the alkaline solution, giving merit that a binary PS/Ni nanostructure without Si oxides can be successfully achieved. © 2003 The Electrochemical Society. All rights reserved.
53 citations
TL;DR: In this paper, polycrystalline silicon thin films were explored with respect to their application as low-impedance microelectrodes for extracellular stimulation and recording of cells.
53 citations
References
More filters
TL;DR: In this article, the properties of electrolyte-semiconductor barriers are described, with emphasis on germanium, and the use of these barriers in localizing electrolytic etching is discussed.
Abstract: Properties of electrolyte-semiconductor barriers are described, with emphasis on germanium. The use of these barriers in localizing electrolytic etching is discussed. Other localization techniques are mentioned. Electrolytes for etching germanium and silicon are given.
1,039 citations
TL;DR: It is found that a standard, widespread, chemical-preparation method for silicon, oxidation followed by an HF etch, results in a surface which from an electronic point of view is remarkably inactive, which has implications for the ultimate efficiency of silicon solar cells.
Abstract: We have found that a standard, widespread, chemical-preparation method for silicon, oxidation followed by an HF etch, results in a surface which from an electronic point of view is remarkably inactive. With preparation in this manner, the surface-recombination velocity on Si111g is only 0.25 cm/sec, which is the lowest value ever reported for any semiconductor. Multiple-internal-reflection infrared spectroscopy shows that the surface appears to be covered by covalent Si-H bonds, leaving virtually no surface dangling bonds to act as recombinatiuon centers. These results have implications for the ultimate efficiency of silicon solar cells.
910 citations
TL;DR: In this paper, multiple internal infrared reflection spectroscopy has been used to identify the chemical nature of chemically oxidized and subsequently HF stripped silicon surfaces, and these very inert surfaces are found to be almost completely covered by atomic hydrogen.
Abstract: Multiple internal infrared reflection spectroscopy has been used to identify the chemical nature of chemically oxidized and subsequently HF stripped silicon surfaces. These very inert surfaces are found to be almost completely covered by atomic hydrogen. Results using polarized radiation on both flat and stepped Si(111) and Si(100) surfaces reveal the presence of many chemisorption sites (hydrides) that indicate that the surfaces are microscopically rough, although locally ordered. In particular, the HF‐prepared Si(100) surface appears to have little in common with the smooth H‐saturated Si(100) surface prepared in ultrahigh vacuum.
588 citations
TL;DR: In this article, the authors measured hydrogen desorption from monohydride and dihydride species on crystalline-silicon surfaces using transmission Fourier-transform infrared (FTIR) spectroscopy.
Abstract: Hydrogen desorption kinetics from monohydride and dihydride species on crystalline-silicon surfaces were measured using transmission Fourier-transform infrared (FTIR) spectroscopy. The FTIR desorption measurements were performed in situ in an ultrahigh-vacuum chamber using high-surface-area porous-silicon samples. The kinetics for hydrogen desorption from the monohydride and dihydride species was monitored using the SiH stretch mode at 2102 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ and the ${\mathrm{SiH}}_{2}$ scissors mode at 910 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, respectively. Annealing studies revealed that hydrogen from the ${\mathrm{SiH}}_{2}$ species desorbed between 640 and 700 K, whereas hydrogen from the SiH species desorbed between 720 and 800 K. Isothermal studies revealed second-order hydrogen desorption kinetics for both the monohydride and dihydride surface species. Desorption activation barriers of 65 kcal/mol (2.82 eV) and 43 kcal/mol (1.86 eV) were measured for the monohydride and dihydride species, respectively. These desorption activation barriers yield upper limits of 84.6 kcal/mol (3.67 eV) and 73.6 kcal/mol (3.19 eV) for the Si-H chemical bond energies of the SiH and ${\mathrm{SiH}}_{2}$ surface species.
479 citations