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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Proceedings Article•
01 Dec 2009TL;DR: The use of nano-Si in the form of Si nanocrystals in the main building blocks of Silicon Photonics (waveguides, modulators, sources and detectors) is reviewed and discussed in this paper.
Abstract: Silicon Photonics is no more an emerging field of research and technology but a present reality with commercial products available on the market, where low dimensional silicon (nanosilicon or nano-Si) can play a fundamental role. After a review of the field, the optical properties of silicon reduced to nanometric dimensions are introduced. The use of nano-Si, in the form of Si nanocrystals, in the main building blocks of Silicon Photonics (waveguides, modulators,sources and detectors) is reviewed and discussed. Recent advances of nano-Si devices such as waveguides,optical resonators (linear,rings and disks) are treated. Large emphasis is dedicated to the visible optical gain properties of nano-Si and to the sensitization effect on Er ions to achieve infrared light amplifications. The possibility of electrical injection in the light emitting diodes is presented as well as the recent development addressed to exploit nano-Si for solar cells. In addition, nonlinear optical effects which will enable fast all-optical switches are described.
74 citations
TL;DR: The electrochemiluminescence of porous silicon with a different surface chemistry displayed an apparently different dynamic ECL process, and an image-contrast technology was established on the basis of the intrinsic mechanism of the ECL dynamic process.
Abstract: The electrochemiluminescence (ECL) of porous silicon (pSi) has attracted great interest for its potential application in display technology and chemical sensors. In this study, we found that pSi with a different surface chemistry displayed an apparently different dynamic ECL process. An image-contrast technology was established on the basis of the intrinsic mechanism of the ECL dynamic process. As a proof of principle, the visualization of latent fingerprints (LFPs) and in situ detection of TNT in fingerprints was demonstrated by using the ECL-based image-contrast technology.
73 citations
TL;DR: In this paper, fast-proton irradiation prior to electrochemical etching for three-dimensional microfabrication in bulk p-type silicon has been proposed, which increases the resistivity of the irradiated regions and acts as an etch stop for porous silicon formation.
Abstract: We report an alternative technique which utilizes fast-proton irradiation prior to electrochemical etching for three-dimensional microfabrication in bulk p-type silicon. The proton-induced damage increases the resistivity of the irradiated regions and acts as an etch stop for porous silicon formation. A raised structure of the scanned area is left behind after removal of the unirradiated regions with potassium hydroxide. By exposing the silicon to different proton energies, the implanted depth and hence structure height can be precisely varied. We demonstrate the versatility of this three-dimensional patterning process to create multilevel free-standing bridges in bulk silicon, as well as submicron pillars and high aspect-ratio nanotips.
73 citations
TL;DR: In this article, by means of molecular dynamics atomistic models, small nc-Si embedded into defect-free silicon chips are constructed using two different classical interatomic potentials, allowing analysis of the defects at the interface which may serve as radiative and nonradiative recombination centers for excitons formed in nc's and, thus, be responsible for the optical properties of the structure.
Abstract: An efficient means to obtain light emission from a silicon-based material would enable integrating both optical and electronic functionalities on the same silicon chips. The long radiative lifetimes have until recently obstructed efficient light emission from Si. A nanocrystalline approach has opened up a prospect for silicon in the optoelectronics application field. However, the structure of the nanocrystal-matrix interface, which appears to be important for the light emission, remains unclear. In the present work, by means of molecular dynamics atomistic models, small nc-Si embedded into defect-free $a\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{2}$ are constructed using two different classical interatomic potentials. The models allow analysis of the defects at the interface which may serve as radiative and nonradiative recombination centers for excitons formed in nc's and, thus, be responsible for the optical properties of the structure. We analyzed the interface structures after a series of high-temperature annealing runs and subsequent relaxation at room temperature. The results show that the $\mathrm{nc}\text{\ensuremath{-}}\mathrm{Si}∕\mathrm{Si}{\mathrm{O}}_{2}$ interface is organized by means of a thin suboxide layer $(\mathrm{Si}{\mathrm{O}}_{2\ensuremath{-}x})$, which contains a considerable amount of undercoordinated defects as well. We also observed the spontaneous formation of silanone bonds $(\mathrm{Si}\mathrm{O})$, frequently discussed in the literature to be centers with an important role on the optical properties of the nc structures.
73 citations
TL;DR: A variety of monolayers anchored directly onto silicon surfaces without an oxide interlayer, their formation mechanisms, their technological applications, and the authors' personal views on the future prospects for this field are described.
Abstract: This article describes a variety of monolayers anchored directly onto silicon surfaces without an oxide interlayer, their formation mechanisms, their technological applications, and our personal views on the future prospects for this field. The chemical modification of non-oxidized silicon surfaces utilizing monolayers was first reported in 1993. The basic finding that a non-oxidized silicon surface could be neutralized with alkyl chains through direct covalent linkage, i.e., silicon-carbon, has offered chemical scientists ease of handling even in an ambient environment and, thus, research has been predictably focused on forming anti-stiction coating films for nano- and micro-electromechanical systems (NEMS/MEMS). Such surface reforming has also been achieved by using other monolayers, which form interfacial bonds, e.g., silicon-nitrogen and silicon-oxygen. The resultant monolayer surfaces are useful for silicon-based applications including molecular electron transfer films, monolayer templates, molecular insulators, capsulators, and bioderivatives. Such monolayers are applicable not only for surface modification, but also for manipulating individual nanomaterials. By modifying the terminal groups of monolayers with nanomaterials including nanocrystals and biomolecules, the nanomaterials can remarkably be immobilized directly onto non-oxidized silicon surfaces based on the formation mechanisms of the monolayer. Such immobilizations will revolutionize the analysis of the specific features and capabilities of individual nanomaterials. Furthermore, the path will be opened for the development of more advanced monolayer-derived chip technology. To achieve this goal, it is extremely important to thoroughly understand the functionalization processes on silicon, since the resultant internal structures and properties of monolayer-derivative silicon may strongly depend on their course of formation.
73 citations
References
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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