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 photoluminescence properties of H-rich amorphous silicon oxide thin films grown in a dual-plasma chemical vapor deposition reactor have been related to a number of stoichiometry and structure characterizations.
Abstract: In order to understand the radiative recombination mechanisms in silicon oxides, photoluminescence properties (PL) of H-rich amorphous silicon oxide thin films grown in a dual-plasma chemical vapor deposition reactor have been related to a number of stoichiometry and structure characterizations (x-ray photoelectron spectroscopy, vibrational spectroscopy, and gas evolution studies). The visible photoluminescence at room temperature from a-SiOx:H matrixes with different compositions, including different bonding environments for H atoms, has been studied in the as-deposited and annealed states up to 900 °C. Three commonly reported PL bands centered around 1.7, 2.1, and 2.9 eV have been detected from the same type of a-SiOx:H material, only by varying the oxygen content (x = 1.35, 1.65, and 2). Temperature quenching experiments are crucial to distinguish the 1.7 eV band, fully consistent with bandtail-to-bandtail recombination, from the radiative defect luminescence mechanisms attributed either to defects rel...
67 citations
TL;DR: In this article, a new photoluminescent material has been synthesized by the interaction of (3-aminopropyl)triethoxysilane with acetic acid under oxygen-free conditions.
Abstract: A new photoluminescent material has been synthesized by the interaction of (3-aminopropyl)triethoxysilane with acetic acid under oxygen-free conditions. The photophysical properties of this material in bulk form, colloidal solution, and thin films have been studied by absorption, excitation, steady-state fluorescence, time-resolved fluorescence, and Fourier transform infrared spectroscopy. These studies showed the existence of two distinct luminescent species emitting bright blue or yellow photoluminescence.
67 citations
TL;DR: In this paper, three reactions are discussed which accomplish a high degree of substitution of the silicon hydride bonds on the porous silicon (pSi) surface with silicon-carbon bonds.
Abstract: Three reactions are discussed which accomplish a high degree of substitution of the silicon hydride bonds on the porous silicon (pSi) surface with silicon–carbon bonds. Lewis acid mediated (LAM) and white light-promoted (LP) hydrosilylation of alkynes and alkenes gives surfaces with alkenyl and alkyl residues, respectively. Evidence for the silicon–carbon bonds is given by solid-state NMR spectroscopy of free-standing pSi material. The extent of the substitution of the surface bonds is termed reaction efficiency (E) which is measured by the change in the integrated area of the silicon hydride stretch region in FTIR spectra (2000–2200 cm—1). The LAM hydrosilylation gives a higher E value than the LP reaction. The E value of the LAM reaction is believed to be limited by the efficiency of the catalyst diffusion throughout the porous structure. In the case of the LP reaction, it is limited by the relative quantity of visible light-exposed material in comparison to the entire amount of IR-apparent silicon hydride bonds. The cathodic electrografting (CEG) reaction gives directly attached alkynyl residues via reduction of a silicon hydride bond to generate alkynyl carbanions, which then react with silicon–silicon bonds.
67 citations
TL;DR: In this article, the microstructure of porous silicon layers has been studied by means of x-ray diffraction using a double-crystal diffractometer, the observed diffraction patterns give directly the mismatch between the lattice parameters of the porous layers and of the substrate, and the curvature of various porous silicon samples obtained in different conditions.
Abstract: The microstructure of porous silicon layers has been studied by means of x‐ray diffraction. Using a double‐crystal diffractometer, the observed diffraction patterns give directly the mismatch between the lattice parameters of the porous layers and of the substrate, and the curvature of various porous silicon samples obtained in different conditions. From measurements with the same experimental set‐up, but with a larger scan range, broad diffuse bumps produced by the pore structure have been observed. This new feature allows us to obtain structural informations on the porous silicon in a nondestructive way. In particular, we have observed the anisotropic pattern showing a preferential elongation of the pores perpendicular to the (100) surface.
67 citations
TL;DR: In this article, a patterned surface of crystalline p-type silicon was fabricated by anodization of patterned surfaces of silicon dioxide and silicon nitride, which exhibited strong red luminescence under UV excitation.
67 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