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.
Citations
More filters
TL;DR: In this paper, metal-assisted chemical etching is applied to produce porous silicon (PS) in a cheap and fast way, which enables the fabrication of porous silicon with different morphologies, pore distribution, and thickness by varying the deposited metal type and thickness, and the Si doping type and level.
Abstract: The application of porous silicon (PS) as a filter substrate in microstructured systems is a promising field of research. Based on this approach, metal-assisted chemical etching is applied to produce PS in a cheap and fast way. This simple and effective method enables the fabrication of PS with different morphologies, pore distribution, and thickness by varying the deposited metal type and thickness, and the Si doping type and level. The metal (Au, Pt) is sputtered in varied thicknesses on patterned p- or n-doped silicon wafers. The etching solution consists of an 1:1:1 mixture of HF:H 2 O 2 :EtOH. Etching time and temperature are varied showing a direct effect on the pore depth. To obtain a thin permeable porous Si layer, advanced silicon etching is used to microstructure the back side of the patterned wafer. Hence, the resulting PS layers turn to thin membranes ∼150 μm thick, maintaining the desired mechanical stability at enhanced gas-permeation rates and thus face a very auspicious career as gas diffusion substrates.
77 citations
TL;DR: Er-doped nanocrystalline Si (nc-Si) waveguides were fabricated on Si substrates and investigated by optical pumping as discussed by the authors, and a stimulated emission at 1540 nm was demonstrated at room temperature.
Abstract: Er-doped nanocrystalline Si (nc-Si) waveguides were fabricated on Si substrates and investigated by optical pumping. A stimulated emission at 1540 nm was demonstrated at room temperature. The sizes of the fabricated Er-doped nc-Si waveguides were 5000 nm×200 nm×L, where L is the cavity length and is changed from 1 to 10 mm. Superlinear optical outputs at 1540 nm were observed for the waveguides longer than 3 mm. The threshold of the optical output where the stimulated emission occurs is in the order of 10 MW/cm2, and is demonstrated to depend on the cavity length of the waveguides. A large reduction of decay lifetimes of the light output from a cleavage facet of the Er-doped nc-Si waveguides was observed when the pumping power density exceeded the thresholds indicating an increase of transition probabilities in intra-4f electrons in Er3+ ions caused by the stimulated emission. Better 1540 nm laser performance and lower pumping power density should be obtained by optimizing the device structure and increas...
77 citations
01 Mar 1995-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the photoluminescence of microcrystalline silicon formed in SiO2 layers by ion beam synthesis was investigated, and the implanted layers were analyzed by Rutherford Backscattering Spectroscopy (RBS), Cross-Sectional Transmission Electron Microscope (XTEM) and Photolumine (PL) using an Ar laser of 488 nm wavelength.
Abstract: We have investigated the photoluminescence of microcrystalline silicon formed in SiO2 layers by ion beam synthesis. 28Si+ ions over the dose range 1 × 1017 to 6 × 1017 cm−2 at energies of 150 keV and 200 keV were implanted into thermal oxide. Samples were annealed in a halogen lamp furnace at temperatures of 900°C, 1100°C and 1300°C for times between 15 and 120 min. The implanted layers were analysed by Rutherford Backscattering Spectroscopy (RBS), Cross-Sectional Transmission Electron Microscope (XTEM) and Photoluminescence (PL) (80 K to 300 K) using an Ar laser of 488 nm wavelength. Room temperature (300 K) visible photoluminescence has been observed from all the samples. XTEM confirms the existence of Si microcrystals (within the SiO2 layers), which typically have a diameter within the range of 2–15 nm. The luminescence peak wavelength was about 600 nm or 800 nm, depending upon processing. Changes in the peak wavelength and intensity from these samples and other samples in which the crystallites were reduced in size by thermal oxidation, show trends which are generally consistent with quantum confinement, however, other mechanisms cannot be ruled out.
77 citations
TL;DR: In this article, visible photoluminescence (PL) can be observed in a-SiOx and aSiOx:H alloys prepared by evaporation of SiO in ultrahigh vacuum and under a flow of hydrogen ions, respectively.
Abstract: Visible photoluminescence (PL) can be observed in a-SiOx and a-SiOx:H alloys prepared by evaporation of SiO in ultrahigh vacuum and under a flow of hydrogen ions, respectively. The hydrogen and oxygen bonding is studied by infrared spectrometry. The hydrogen stability is followed by thermal desorption spectrometry experiments. The evolution of the PL with annealing treatments shows that the PL can be attributed to a quantum confinement effect in a-Si clusters embedded in the matrix of a-SiOx. Hydrogen does not greatly contribute to the PL efficiency and to the thermal evolution of the a-Si clusters.
77 citations
Book•
07 Aug 2014TL;DR: In this article, a survey of the properties, effects, roles, and characterization of extended defects in semiconductors is presented, with a focus on point defect maldistributions.
Abstract: The elucidation of the effects of structurally extended defects on electronic properties of materials is especially important in view of the current advances in electronic device development that involve defect control and engineering at the nanometer level. This book surveys the properties, effects, roles and characterization of extended defects in semiconductors. The basic properties of extended defects (dislocations, stacking faults, grain boundaries, and precipitates) are outlined, and their effect on the electronic properties of semiconductors, their role in semiconductor devices, and techniques for their characterization are discussed. These topics are among the central issues in the investigation and applications of semiconductors and in the operation of semiconductor devices. The authors preface their treatment with an introduction to semiconductor materials and conclude with a chapter on point defect maldistributions. This text is suitable for advanced undergraduate and graduate students in materials science and engineering, and for those studying semiconductor physics.
76 citations
References
More filters
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