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.
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TL;DR: The pseudopotential density functional method (PDFM) as mentioned in this paper combines pseudopotentials and density functional theory to determine the electronic structure of matter, which is the most popular technique for examining a wide range of structural and electronic properties.
Abstract: In this review, I will describe the combination of pseudopotentials and density functional theory to determine the electronic structure of matter. This combination, called the pseudopotential-density functional method (PDFM), represents the most popular technique for examining a wide range of structural and electronic properties. I will illustrate applications of the PDFM to problems of current interest: nanostructures and other complex confined systems.
104 citations
TL;DR: Copper on porous silicon (Cu/PSi) nanocomposite powder is a new electrode material synthesized by electrodeless deposition of copper nanoparticles on the etched PSi powder in a solution containing hydrofluoric acid and CuSO4 as discussed by the authors.
Abstract: Copper on porous silicon (Cu/PSi) nanocomposite powder is a new electrode material synthesized by electrodeless deposition of copper nanoparticles on the etched PSi powder in a solution containing hydrofluoric acid and CuSO4. The nanocomposite is selective for electrochemical hydrogen peroxide (H2O2) reduction and shows a wide linear range (0.50–3.78 mmol L−1), low detection limit (0.27 μmol L−1), fast response (less than 5 s), good signal reproducibility (R.S.D. = 1.5%), long-term stability (more than one month), plus the low cost. No interference was observed from common species such as ascorbic acid, dopamine, uric acid and glucose.
103 citations
TL;DR: In this paper, a soft x-ray excited optical luminescence (XEOL) and xray emission spectroscopy (XES) study of silicon nanowires (SiNW) with excitations at the silicon $K$ and ${L}_{3,2}$ edge, respectively.
Abstract: We report a soft x-ray excited optical luminescence (XEOL) and x-ray emission spectroscopy (XES) study of silicon nanowires (SiNW) with excitations at the silicon $K$ and ${L}_{3,2}$ edge, respectively. It is found that the XEOL of SiNW exhibits several luminescence bands at $\ensuremath{\sim}460$, $\ensuremath{\sim}530$, and $\ensuremath{\sim}630\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. These luminescence bands are broad and are sensitive to the $\mathrm{Si}\phantom{\rule{0.2em}{0ex}}1s$ excitation channel (Si versus $\mathrm{Si}{\mathrm{O}}_{2}$ whiteline). These chemical- and morphology-dependent luminescences are attributable to the emission from the encapsulating silicon oxide, the quantum-confined silicon crystallites of various sizes embedded in the oxide layer, and the silicon-silicon oxide interface. XES clearly shows the presence of a relatively thick oxide layer encapsulating the silicon nanowire and the densities of states tailing across the Fermi level. The implications of these findings to the electronic and optical properties of silicon nanowires are discussed.
103 citations
TL;DR: P porous silicon as a host material for enzyme immobilization is emphasized, the working principle, mechanism, kinetics of an enzyme-based biosensor for chromium detection is elaborated and several schemes on porous silicon-based immobilized enzyme biosensors for the detection of chromium in potable water are proposed.
103 citations
TL;DR: In this article, a silicon nanostructured pn junction diode using current injection at room temperature was observed to exhibit stimulated emission at bandgap energy of 1.1 eV, where the spatial confinement of carriers through such localization structures contributes to the enhancement of the stimulated emission.
Abstract: Stimulated emission at bandgap energy of 1.1 eV was observed in a silicon nanostructured pn junction diode using current injection at room temperature. Nonuniform diffusion using spin-on boron dopant mixed with silicon dioxide nanoparticles was used to fabricate the device. The spatial confinement of carriers through such localization structures contributes to the enhancement of the stimulated emission. The experimental results show a drastic increase in the optical power and multiple spectral peaks at wavelengths longer than the main peak of spontaneous emission through various phonon-assisted radiative recombination processes. When the injection current significantly exceeds a threshold, a single peak dominates, exhibiting stimulated emission.
103 citations
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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