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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79 citations
TL;DR: In this article, the authors identify the silicon nitride matrix itself as responsible for the photoluminescence, and conclude that silicon nanocrystal films are inappropriate if one aims at investigating photolumininescence from silicon nanoparticles within such a matrix.
Abstract: Silicon nitride compounds emit photoluminescence all over the visible range. Recent studies ascribed this luminescence to quantum-size effects within silicon nanocrystals that were either shown or assumed to form inside the silicon nitride matrix; the luminescence of the matrix itself was ignored. In contrast, observing the same luminescence even without the presence of silicon crystallites, our work identifies the silicon nitride matrix itself as responsible for the photoluminescence. All experimental observations are well explained by band tail luminescence from the silicon matrix. In contrast to the silicon nanocrystal approach, our model explains all aspects of the luminescence. As a consequence, we conclude that silicon nitride films are inappropriate if one aims at investigating photoluminescence from silicon nanocrystals within such a matrix.
79 citations
TL;DR: In this article, SiO2 films were co-implanted with Si and C ions, followed by 1100°C annealing for 60 min, and the intensity of short-wavelength photoluminescence was observed.
Abstract: Intense short-wavelength photoluminescence (PL) observed at room temperature from thermal SiO2 films co-implanted with Si and C is reported. A flat Si profile was first implanted, followed by 1100 °C annealing for 60 min. C ions were subsequently used to be implanted into the same depth region. PL was observed from the as-implanted samples with and without annealing. The PL intensity increases with annealing temperature. Comparing the PL spectra and the PL dynamics of the C-implanted, annealed, Si-implanted (CIASI) SiO2 films with those from Si- and C-implanted SiO2 films suggests that the interaction of Si and C in SiO2 films plays an important role in the luminescence in CIASI SiO2 films.
78 citations
TL;DR: In this article, the preparation of discrete erbium-doped silicon nanoparticles by co-pyrolysis of disilane and the volatile complex Er(tmhd)3 (tmhd = 2,2,6,6-tetramethyl-3,5-heptanedionato) is described.
Abstract: The preparation of discrete erbium-doped silicon nanoparticles prepared by the co-pyrolysis of disilane and the volatile complex Er(tmhd)3 (tmhd = 2,2,6,6-tetramethyl-3,5-heptanedionato) is described. The nanoparticles were characterized by transmission electron microscopy, selected area electron diffraction, X-ray dispersive spectroscopy, photoluminescence, and UV−visible absorption spectroscopies. Erbium-doped silicon nanoparticles possess a distinctive dark contrast in the transmission electron microscope, and the presence of erbium is confirmed by X-ray energy dispersive spectroscopy. The mean diameter of the nanoparticle aggregates can be shifted by altering the length of the pyrolysis oven employed. Chacteristic Er3+ near-infrared photoluminescence at 1540 nm is detected in these doped nanoparticles; preliminary excitation and power dependence measurements of this luminescence suggest a carrier-mediated emission mechanism.
78 citations
TL;DR: In this article, a novel technique for the formation and lift-off of thin porous silicon films from starting substrates in a single step by electrochemical etching in hydrofluoric acid-based solutions is described.
Abstract: A novel technique for the formation and lift-off of thin porous silicon films from starting substrates in a single step by electrochemical etching in hydrofluoric acid-based solutions is described. Lift-off or separation of porous silicon (PS) film occurs under specific sets of current density and HF concentration, which also determines the PS film thickness that can vary from a few micrometers to a few tens of micrometers. A model based on a diffusion-limited mass transfer of HF molecules from the bulk of the solution to the point of reaction at the pore tip is proposed to explain the lift-off phenomena. Based on this an expression for expected PS film thickness and separation time as a function of current density and hydrofluoric acid concentration has been derived. The experimental results are in agreement with the proposed medel.
78 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