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 preparation of ordered and arranged Si quantum dots using a SiO/SiO 2 superlattice approach is presented, and the different processes of phase separation and crystallization are studied in detail by infrared (IR) absorption and photoluminescence (PL) spectroscopy for different annealing temperatures from 300 to 1100°C.
Abstract: The preparation of ordered and arranged Si quantum dots using a SiO/SiO 2 superlattice approach is presented. The different processes of phase separation and crystallization are studied in detail by infrared (IR) absorption and photoluminescence (PL) spectroscopy for different annealing temperatures from 300 to 1100°C. IR spectra show a continuous shift of the Si-O-Si asymmetric stretching mode to higher energies with increasing annealing temperature, which is a sign of phase separation to Si and SiO 2 . Three PL bands are distinguished and correspond to the three processes of phase separation. A band centred at 2.2 eV is present in as-prepared samples and vanishes for annealing above 800°C which is clearly correlated with defects. The second band shifting from 1.7 to 1.4 eV is detected for annealing temperatures between 300 and 900 °C. A strong red luminescence due to quantum confinement is observed for annealing above 900 °C. Our results indicate that the different and seemingly contradictory PL observations in the literature could originate from different states of network reorganization during the phase separation and crystallization processes. The origins of the different IR and PL bands are discussed in comparison with those of bulk crystalline SiO and SiO 2 .
63 citations
Patent•
29 Oct 1993TL;DR: A resonant tunneling diode (400) made of a silicon quantum well with silicon oxide tunneling barriers (404, 408) was proposed in this article. But the tunneling barrier was not designed to insure crystal alignment through the diode.
Abstract: A resonant tunneling diode (400) made of a silicon quantum well (406) with silicon oxide tunneling barriers (404, 408). The tunneling barriers have openings (430) of size smaller than the electron wave packet spread to insure crystal alignment through the diode without affecting the tunneling barrier height.
63 citations
TL;DR: In this article, photoluminescent porous silicon (PSi) patterns of micrometer dimension were produced by the Pt-assisted electroless etching of Si in 1:1:2 methanol:HF:H2O2 Pt-containing squares with side lengths ranging from 125to20μm were defined by a focused-ion-beam-assisted maskless deposition of Pt from an organometallic precursor, trimethylmethylmethylcyclopentadienyl platinum.
Abstract: Photoluminescent porous silicon (PSi) patterns of micrometer dimension were produced by the Pt-assisted electroless etching of Si in 1:1:2 methanol:HF:H2O2 Pt-containing squares with side lengths ranging from 125to20μm were defined by a focused-ion-beam-assisted maskless deposition of Pt from an organometallic precursor, trimethylmethylcyclopentadienyl platinum The Pt-patterned Si samples were then etched to produce photoluminescent pixel arrays with high fidelity transfer of the Pt deposition pattern into luminescent pixels of varying size The morphology of the PSi patterns was correlated with the spatial luminescence characteristics at the individual pixel level Luminescent pixels with feature sizes down to ca 1μm were largely confined to the areas initially coated with Pt, and the morphologies produced within any one set of equal-sized Pt squares were similar For 5-μm pads and larger, the morphologies obtained were an admixture of a porous structure coexisting with deeper heavily etched crater r
63 citations
TL;DR: In this article, the optical behavior of porous silicon mirrors is studied, revealing good performance in the visible wavelength range, and showing a great sensitivity to different liquids infiltrated into the porous structure.
63 citations
TL;DR: In this paper, a broad photoluminescence (PL) band at 1.17 eV was observed for as-anodized porous Ge (PG) at room temperature.
63 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