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Journal ArticleDOI

Silicon quantum wire array fabrication by electrochemical and chemical dissolution of wafers

03 Sep 1990-Applied Physics Letters (American Institute of Physics)-Vol. 57, Iss: 10, pp 1046-1048
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
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Journal ArticleDOI
TL;DR: A turn-on reduction essentially provides a less damaged SiO(x)/Si interface as the required bias for the electroluminescence of the MOSLED is greatly decreased, which thus suppresses the generation of structural damage related radiant defects under a lower biased condition and leads to a more stable near-infrared electrolUMinescence with a narrowing linewidth and an operating lifetime lengthened to >3 hours.
Abstract: The premier observation on the enhanced light emission from such a metal-SiOx-Si light emitting diode (MOSLED) with Si nano-pyramids at SiOx/Si interface is demonstrated at low biases. The Si nano-pyramids exhibits capability in providing the roughness of the SiOx/Si interface, and improving the Fowler-Nordheim (F-N) tunneling mechanism based carrier injection through the novel SiOx/nano-Si-pyramid/Si structure. HRTEM analysis reveals a precisely controllable size and concentration of the crystallized interfacial Si nano-pyramids at 10nm(height)×10nm(width) and within the range of 108-1011 cm-2, respectively. With these Si nano-pyramids at a surface density of up to 1012/cm2, the F-N tunneling threshold can be reduce from 7 MV/cm to 1.4 MV/cm. The correlation between surface density of the interfacial Si nano-pyramids and the threshold F-N tunneling field has been elucidated. Such a turn-on reduction essentially provides a less damaged SiOx/Si interface as the required bias for the electroluminescence of the MOSLED is greatly decreased, which thus suppresses the generation of structural damage related radiant defects under a lower biased condition and leads to a more stable near-infrared electroluminescence with a narrowing linewidth and an operating lifetime lengthened to >3 hours. An output EL power of nearly 150 nW under a biased voltage of 75 V and current density of 32 mA/cm2 is reported for the first time.

62 citations

Journal ArticleDOI
TL;DR: In this article, the radiative lifetime of porous silicon is investigated between liquid helium and room temperature using photoluminescence decay measurements, and the functional dependence of the lifetime on photon energy reveals the confinement character of the recombination carriers.
Abstract: Using photoluminescence decay measurements the radiative lifetime of porous silicon is investigated between liquid helium and room temperature. The radiative recombination mechanism in porous silicon is in essence the same as in bulk silicon, viz. a phonon mediated indirect transition. The functional dependence of the lifetime on photon energy reveals the confinement character of the recombination carriers. The high external photoluminescence efficiency is well explained by the reduction of nonradiative recombination owing to low mobility, to low dimensionality, and to the extreme low surface recombination rate, and is further enhanced by the relatively small refractive index.

62 citations

Journal ArticleDOI
TL;DR: In this article, the photoluminescence (PL) spectral shifts during anodization of porous Si and after immersion in different chemical solutions are attributed to changes in the surface chemistry achieved by changing the composition of the electrolyte in which the samples are immersed.
Abstract: The observation of photoluminescence (PL) spectral shifts during anodization of porous Si and after immersion in different chemical solutions is reported. These shifts in the PL spectra are attributed to changes in the surface chemistry achieved by changing the composition of the electrolyte in which the samples are immersed. Using this approach the emission has been repeatedly cycled (≳100 times) between green and red.

62 citations

Journal ArticleDOI
TL;DR: This study exhaustively reviewed various aspects of QDs, highlighting their pharmaceutical and biomedical applications, pharmacology, interactions, and toxicological manifestations.
Abstract: Quantum dots (QDs) have captured the fascination and attention of scientists due to their simultaneous targeting and imaging potential in drug delivery, in pharmaceutical and biomedical applications. In the present study, we have exhaustively reviewed various aspects of QDs, highlighting their pharmaceutical and biomedical applications, pharmacology, interactions, and toxicological manifestations. The eventual use of QDs is to dramatically improve clinical diagnostic tests for early detection of cancer. In recent years, QDs were introduced to cell biology as an alternative fluorescent probe.

62 citations


Cites methods from "Silicon quantum wire array fabricat..."

  • ...In 1990, efficient light emission from silicon was reported by Canham (Canham 1990)....

    [...]

Journal ArticleDOI
TL;DR: In this article, a facile chemical synthetic method for Si nanoparticles from SiO2 in a liquid environment of molten metal chlorides containing magnesium was presented, and the results showed that Si nanocrystals (NCs) start to grow at 550 °C in the molten salt solvent and that the growth is controllable through the adjustment of the temperature, as well as the type of salt.
Abstract: Silicon is one of the major constituents of the earth's crust and, in its elemental form, the base of many semiconductor applications, including electronics and energy conversion. Downsizing Si to the nanoscale dimension extends its application to diverse fields, which, however, is often plagued by expensive and inefficient fabrication methods. We report herein a facile chemical synthetic method for Si nanoparticles from SiO2 in a liquid environment of molten metal chlorides containing magnesium. The results show that Si nanocrystals (NCs) start to grow at 550 °C in the molten salt solvent and that the growth is controllable through the adjustment of the temperature, as well as the type of salt. We also show that the method can be generalized, as illustrated by the synthesis of Ge nanoparticles at a temperature of 450 °C. The growth of NCs is interpreted in terms of the chemical reduction of oxide by electrons solvated in the molten salts.

62 citations

References
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Journal ArticleDOI
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

Journal ArticleDOI
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

Journal ArticleDOI
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

Journal ArticleDOI
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