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: In this paper, the authors demonstrated a strong room-temperature (RT), infrared (IR) (1.54 μm) emission from Er•implanted red-emitting (peaked at 1.9 eV) porous silicon (Er:PSi).
Abstract: This communication demonstrates a strong, room‐temperature (RT), infrared (IR) (1.54 μm) emission from Er‐implanted red‐emitting (peaked at 1.9 eV) porous silicon (Er:PSi). Erbium was implanted into porous Si, bulk Si, and quartz with a dose of 1015/cm2 at 190 keV and annealed for 30 minutes in N2 at temperatures ranging from 500 °C to 900 °C under identical conditions. No RT IR emission was observed from Er implanted quartz and silicon after annealing at 650 °C (although after annealing at 900 °C very weak emission was observed from quartz at 9 K). The highest RT emission intensity at 1.54 μm was from Er:PSi with a peak concentration of 1.5×1020/cm3 and annealed at 650 °C. Even the luminescence intensity from Er:PSi annealed at 500 °C was 26 times higher than that observed from Er‐implanted quartz at 400 keV and annealed at 900 °C. A reduction in photoluminescence (PL) intensity of about a factor of two from Er:PSi over the 9 to 300 K temperature range was observed which is consistent with Er in wide ban...
59 citations
TL;DR: In this paper, a stable and reproducible electroluminescence (EL) based on nanocrystalline silicon (nc-Si) was observed at room temperature, and it was found that the EL peak was significantly blueshifted from 780 to 600 nm with decreasing the a-Si:H sublayer thickness from 4.0 to 1.0 nm.
Abstract: Nanocrystalline silicon (nc-Si) was fabricated by KrF excimer laser annealing of hydrogenated amorphous silicon/amorphous-SiNx:H superlattices. A stable and reproducible electroluminescence (EL) based on these structures was observed at room temperature. It was found that the EL peak was significantly blueshifted from 780 to 600 nm with decreasing the a-Si:H sublayer thickness from 4.0 to 1.0 nm, while the intensity was also notably enhanced. The results suggest that the quantum confinement effect may play an essential role in visible light emissions from our present samples.
59 citations
TL;DR: In this article, tuning in optoelectronic properties of sputter deposited zinc oxide (ZnO) thin films on ITO coated glass substrate have been investigated as a function of annealing parameters.
59 citations
TL;DR: In this article, the effect of quantum confinement on the direct bandgap of spherical Si nanocrystals has been modelled theoretically, and it was shown that the energy of the direct-bandgap at the Γ-point decreases with size reduction: quantum confinement enhances radiative recombination across the directbandgap and introduces its red shift for smaller grains.
Abstract: The effect of quantum confinement on the direct bandgap of spherical Si nanocrystals has been modelled theoretically. We conclude that the energy of the direct bandgap at the Γ-point decreases with size reduction: quantum confinement enhances radiative recombination across the direct bandgap and introduces its “red“ shift for smaller grains. We postulate to identify the frequently reported efficient blue emission (F-band) from Si nanocrystals with this zero-phonon recombination. In a dedicated experiment, we confirm the “red“ shift of the F-band, supporting the proposed identification.
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TL;DR: In this article, a porous silicon (PS) layer is investigated as a sensing material to detect organic vapours with low concentration, and the sensors were made by applying the technologies of membrane formation by anisotropic etching of silicon and anodization in HF solution.
Abstract: In this paper, a porous silicon (PS) layer is investigated as a sensing material to detect organic vapours with low concentration. To do this, PS sensors with membrane structure were designed and fabricated. The sensors were made by applying the technologies of membrane formation by anisotropic etching of silicon and PS formation by anodization in HF solution. From fabricated sensors, current-voltage (I-V) curves were measured for ethanol (called alcohol), methanol and acetone gases evaporated from 0.1-0.5% solution concentrations at 36°C. As a result, all curves showed rectifying behaviour due to a diode structure between Si and the PS layer. The conductance of our sensors mostly increased along with the organic solution concentration at a high voltage of 5 V, but the built-in potential on the measured I-V curve was lowered with it by the adsorption effect of the organic vapours with high dipole moment.
59 citations
Cites background from "Silicon quantum wire array fabricat..."
...Since porous silicon (PS) was suggested as a potential optical material after the observation [1] of specific photoluminescence phenomena, it has invoked much interest in the development of new silicon light emitting devices....
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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