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: This review overviews the different synthetic methods of inorganic ultrasmall nanoparticles as well as their properties, characterization, surface modification and toxicity, and summarizes the current state of knowledge regarding pharmacokinetics, biodistribution and targeting of nanoscale materials.
232 citations
Cites background from "Silicon quantum wire array fabricat..."
...The first evidence that silicon emits when its size shrinks to the nanoscale, is reported in the work of Canham et al who observed red emission in silicon nanowires in 1990.(283) Many efforts have been done to understand deeply the nature of this luminescence and the debate on the explanation of emission properties in silicon nanoparticles is still open and sometimes controversial....
[...]
ENEA1
TL;DR: In this paper, an antireflection (AR) coating for polycrystalline Si-based solar cells is presented. And the authors demonstrate the feasibility of a very efficient porous Si AR layer, prepared by a simple, cost effective, chemical etching method.
231 citations
TL;DR: In this paper, a solution phase synthesis for producing crystalline silicon nanoclusters at significantly lower temperatures than previously required is reported, which is performed at ambient pressure and yields a particle surface that can be modified by chemical methods.
Abstract: We report here a new solution phase synthesis for producing crystalline silicon nanoclusters at significantly lower temperatures than previously required. In addition, it is performed at ambient pressure and yields a particle surface that can be modified by chemical methods. This method has the potential to yield large amounts of silicon nanocrystals in addition to providing reliable control over size distribution and surface termination. In this synthesis we use the Zintl salt KSi as a starting reagent. KSi is synthesized by reacting excess K with silicon at 650{degree}C for three days and subliming off the excess K at 275{degree}C under vacuum. The purity of the air-sensitive, black solid is verified by powder X-ray diffraction. 23 refs., 1 fig.
230 citations
Patent•
07 Oct 2003TL;DR: In this article, a thin coating of a Raman active metal, such as gold or silver, may be applied to the porous silicon substrate by cathodic electromigration or any known technique, providing an extensive, metal rich environment for SERS, SERRS, hyper-Raman and/or CARS spectroscopy.
Abstract: The methods and apparatus 300 disclosed herein concern Raman spectroscopy using metal coated nanocrystalline porous silicon substrates 240, 340. In certain embodiments of the invention, porous silicon substrates 110, 210 may be formed by anodic etching in dilute hydrofluoric acid 150. A thin coating of a Raman active metal, such as gold or silver, may be coated onto the porous silicon 110, 210 by cathodic electromigration or any known technique. The metal-coated substrate 240, 340 provides an extensive, metal rich environment for SERS, SERRS, hyper-Raman and/or CARS Raman spectroscopy. In certain embodiments of the invention, metal nanoparticles may be added to the metal-coated substrate 240, 340 to further enhance the Raman signals. Raman spectroscopy may be used to detect, identify and/or quantify a wide variety of analytes, using the disclosed methods and apparatus 300.
229 citations
TL;DR: In this article, the authors describe some properties of materials that undergo qualitative, often sudden, changes below a certain size scale and present a general description of these size-dependent properties.
Abstract: Reduction in size often does more than simply make things smaller. There are many properties of materials that undergo qualitative, often sudden, changes below a certain size scale. This Report first describes some of these size-dependent properties. Following this general description, recent developments in a number of selected topics in nanoscience are covered. These topics are: luminescence from Au nanoparticles; Si (and related) nanoparticle luminescence; modification of optical absorption by surface adsorption on nanoparticles; and transistors (and some other devices) based on nanotubes and nanowires.
228 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