silicon and silicon-nitride

Atomic force microscopy (AFM) works by scanning a very tiny tip over a surface with great precision. The microscope tips can be chemically functionalized to improve the images obtained. Well-defined chemical functionalization of AFM tips is especially important for experiments, such as chemical force microscopy and single molecule recognition force microscopy, to examine specific interactions at the single molecular level. In this chapter, we present an overview of chemical modifications of tips that have been reported to date with regards to the proper fixation of probe molecules, focusing particularly on chemical procedures developed to anchor biological molecules on AFM tips.

Topics: Microscopy, Atomic Force; Molecular Imaging; Silicon; Silicon Compounds; Surface Properties

Topics: Biosensing Techniques; DNA; Graphite; Nanopores; Optical Imaging; Silicon; Silicon Compounds; Spectrum Analysis, Raman

Helium ion microscopy (HIM) scans samples with a fine ion beam exploiting the very short de Broglie wavelength of helium ions. Because the radiation induces only a small sample region to emit secondary electrons (SEs), very high resolution is expected. In order to explore the applications of SE-HIM in biology, COS7 kidney fibroblast cells and C2C12 myoblast cells cultured on a silicon (Si) nitride (SiN)/Si bilayer were dried and directly observed in high vacuum, without coating or staining. High contrast, high depth-of-field images were obtained revealing the nucleus, endoplasmic reticulum, cytoskeleton and putative mitochondria above a bright background from the support. Gold-tagged antibodies were employed to aid organelle identification. Signals from the gold tags were most clearly distinguishable by secondary electron (SE)-HIM when cells were grown on thin SiN film, and the minimum gap measured between gold particles showed the resolution to be 2 nm. Wheat germ agglutinin-gold labeling revealed clusters of gold particles ~50-200 nm in diameter on COS7 cells, which might represent assemblies of glycosylated proteins, suggesting the formation of membrane raft structures that include membrane proteins. SE-HIM also delivered high contrast images of unstained, uncoated, thin sections of Epon‑embedded mouse kidney tissues mounted on a SiN/Si bilayer, revealing the details of sub-tissues and cell organelles. A charge-coupled mechanism explaining the observed SE-HIM contrast is proposed. Ionoluminescence-HIM was also performed targeting zinc oxide particles on cells. In conclusion, the high depth-of-field, high-resolution imaging achieved using HIM may have applications in various fields, including soft materials.

Topics: Actins; Animals; Chlorocebus aethiops; Colloids; COS Cells; Endoplasmic Reticulum; Fibroblasts; Fluorescence; Helium; Immunohistochemistry; Ions; Kidney; Mice; Microscopy; Microtubules; Mitochondria; Myoblasts; Polysaccharides; Silicon; Silicon Compounds; Staining and Labeling; Stress Fibers; Tubulin

We report a novel low-noise nanopore device employing a polymer substrate. The Si substrate of a fabricated Si-substrate-based silicon nitride (Si3N4) membrane was replaced with a polymer substrate. As such, laser machining was used to make a micro-size hole through the polyimide (PI) substrate, and a thin Si3N4 membrane was then transferred onto the PI substrate. Finally, a nanopore was formed in the membrane using a transmission electron microscope for detection of biomolecules. Compared to the Si-substrate-based device, the dielectric noise was greatly reduced and the root-mean-square noise level was decreased from 146.7 to 5.4 pA. Using this device, the translocation of double-strand deoxyribonucleic acid (DNA) was detected with a high signal/noise (S/N) ratio. This type of device is anticipated to be available for future versatile sequencing technologies.

Topics: DNA; Ions; Light; Membranes, Artificial; Microscopy, Electron, Transmission; Nanopores; Nanotechnology; Polymers; Signal-To-Noise Ratio; Silicon; Silicon Compounds

In situ transmission electron microscopy (TEM) electronic transport measurements in nanoscale systems have been previously confined to two-electrode configurations. Here, we use the focused electron beam of a TEM to fabricate a three-electrode geometry from a continuous 2D material where the third electrode operates as side gate in a field-effect transistor configuration. Specifically, we demonstrate TEM nanosculpting of freestanding graphene sheets into graphene nanoribbons (GNRs) with proximal graphene side gates, together with in situ TEM transport measurements of the resulting GNRs, whose conductance is modulated by the side-gate potential. The TEM electron beam displaces carbon atoms from the graphene sheet, and its position is controlled with nanometer precision, allowing the fabrication of GNRs of desired width immediately prior to each transport measurement. We also model the corresponding electric field profile in this three-terminal geometry. The implementation of an in situ TEM three-terminal platform shown here further extends the use of a TEM for device characterization. This approach can be easily generalized for the investigation of other nanoscale systems (2D materials, nanowires, and single molecules) requiring the correlation of transport and atomic structure.

Topics: Computer Simulation; Diffusion; Electrodes; Electrons; Graphite; Microscopy, Electron, Transmission; Nanotubes, Carbon; Particle Size; Silicon; Silicon Compounds; Surface Properties

The proposed approach demonstrated in this study provides an immunosensing system based on reflectometric interference spectroscopy (RIfS) in combination with an antibody immobilization method using histidine-tagged recombinant protein A. Carboxymethyldextran (CMD) was immobilized on a 3-aminopropyltriethoxysilane-treated a silicon nitride-coated silicon wafer, followed by chelating histidine-tagged recombinant protein A with copper (II) ions. The CMD-layer was found to be advantageous in terms of not only immobilization of histidine-tagged recombinant protein A-mediated an antibody against myoglobin (anti-Myo) but also prevention of non-specific binding of myoglobin. Myoglobin was repeatedly detected, and the apparent detection limit was 0.1 μg mL(-1). The proposed RIfS-based protein sensing system, in conjunction with the easy preparation of silicon-based inexpensive immunosensing chips, is expected to be applicable for label-free optical detection for other proteins in various fields.

Topics: Antibodies, Immobilized; Biosensing Techniques; Copper; Dextrans; Histidine; Myoglobin; Propylamines; Recombinant Proteins; Silanes; Silicon; Silicon Compounds; Spectrum Analysis

In this paper, we report on the measurement and modeling of enhanced optical refractometric sensors based on whispering gallery modes. The devices under test are optical microresonators made of silicon nitride on silicon oxide, which differ in their sidewall inclination angle. In our approach, these microresonators are vertically coupled to a buried waveguide with the aim of creating integrated and cost-effective devices. Device modeling shows that the optimization of the device is a delicate balance of the resonance quality factor and evanescent field overlap with the surrounding environment to analyze. By numerical simulations, we show that the microdisk thickness is critical to yield a high figure of merit for the sensor and that edge inclination should be kept as high as possible. We also show that bulk-sensing figures of merit as high as 1600 RIU(-1) (refractive index unit) are feasible.

Topics: Biosensing Techniques; Optical Devices; Refractometry; Silicon; Silicon Compounds

Flexible integrated photonic devices based on crystalline materials on plastic substrates have a promising potential in many unconventional applications. In this Letter, we demonstrate a fully integrated photonic system including ring resonators and grating couplers, based on both crystalline silicon and silicon nitride, on flexible plastic substrate by using the stamping-transfer method. A high yield has been achieved by a simple, yet reliable transfer method without significant performance degradation.

Topics: Biosensing Techniques; Nanostructures; Nanotechnology; Optical Devices; Optical Phenomena; Polyethylene Glycols; Polyethylene Terephthalates; Silicon; Silicon Compounds

A significant enhancement of blue light emission from amorphous oxidized silicon nitride (a-SiNx:O) films is achieved by introduction of ordered and size-controllable arrays of Ag nanoparticles between the silicon substrate and a-SiNx:O films. Using hexagonal arrays of Ag nanoparticles fabricated by nanosphere lithography, the localized surface plasmons (LSPs) resonance can effectively increase the internal quantum efficiency from 3.9% to 13.3%. Theoretical calculation confirms that the electromagnetic field-intensity enhancement is through the dipole surface plasma coupling with the excitons of a-SiNx:O films, which demonstrates a-SiNx:O films with enhanced blue emission are promising for silicon-based light-emitting applications by patterned Ag arrays.

Topics: Light; Metal Nanoparticles; Nanotechnology; Optics and Photonics; Silicon; Silicon Compounds; Surface Plasmon Resonance

We report the formation of POPC lipid bilayers that span 130 nm pores in a freestanding silicon nitride film supported on a silicon substrate. These solvent-free lipid membranes self-assemble on organosilane-treated Si3N4 via the fusion of 200 nm unilamellar vesicles. Membrane fluidity is verified by fluorescence recovery after photobleaching (FRAP), and membrane resistance in excess of 1 GΩ is demonstrated using electrical impedance spectroscopy (EIS). An array of 40,000 membranes maintained high impedance over 72 h, followed by rupture of most of the membranes by 82 h. Membrane incorporation of gramicidin, a model ion channel, resulted in increased membrane conductance. This membrane conductance was diminished when the gramicidin channels were blocked with CaCl2, indicating that the change in membrane conductance results from gramicidin-mediated ion transport. These very stable, biologically functional pore-spanning membranes open many possibilities for silicon-based ion-channel devices for applications such as biosensors and high-throughput drug screening.

Topics: Biological Transport; Cell Membrane; Gramicidin; Ions; Lipid Bilayers; Nanopores; Silicon; Silicon Compounds; Surface Properties

Atomic force microscopy (AFM) is used extensively for the investigation of noncovalent molecular association. Although the technique is used to derive various types of information, in almost all instances the frequency of complex formation, the magnitude of rupture forces, and the shape of the force-distance curve are used to determine the behavior of the system. We have used AFM to consider the effect of contact force on the unbinding profiles of lactose-galectin-3, as well as the control pairs lactose-KDPG aldolase, and mannose-galectin-3, where the interacting species show negligible solution-phase affinity. Increased contact forces (>250 pN) resulted in increased probabilitites of binding and decreased blocking efficiencies for the cognate ligand-receptor pair lactose-G3. Increased contact force applied to two control systems with no known affinity, mannose-G3 and lactose-KDPG aldolase, resulted in nonspecific ruptures that were indistinguishable from those of specific lactose-G3 interactions. These results demonstrate that careful experimental design is vital to the production of interpretable data, and suggest that contact force minimization is an effective technique for probing the unbinding forces and rupture lengths of only specific ligand-receptor interactions.

Topics: Aldehyde-Lyases; Animals; Galectin 3; Histidine; Immobilized Proteins; Lactose; Mannose; Mice; Microscopy, Atomic Force; Oligopeptides; Recombinant Fusion Proteins; Silicon; Silicon Compounds

We demonstrate a vertical integration of high-Q silicon nitride microresonators into the silicon-on-insulator platform for applications at the telecommunication wavelengths. Low-loss silicon nitride films with a thickness of 400 nm are successfully grown, enabling compact silicon nitride microresonators with ultra-high intrinsic Qs (~ 6 × 10(6) for 60 μm radius and ~ 2 × 10(7) for 240 μm radius). The coupling between the silicon nitride microresonator and the underneath silicon waveguide is based on evanescent coupling with silicon dioxide as buffer. Selective coupling to a desired radial mode of the silicon nitride microresonator is also achievable using a pulley coupling scheme. In this work, a 60-μm-radius silicon nitride microresonator has been successfully integrated into the silicon-on-insulator platform, showing a single-mode operation with an intrinsic Q of 2 × 10(6).

Topics: Computer-Aided Design; Electric Conductivity; Equipment Design; Equipment Failure Analysis; Micro-Electrical-Mechanical Systems; Miniaturization; Silicon; Silicon Compounds; Telecommunications; Transducers

The development of enzymatic sensors for biological purposes such as biomedicine, pharmacy, food industry, and environmental toxicity requires the purification step of the enzyme. To prevent the loss of the enzyme activity, a new strategy is held in order to immobilize the bacteria. It will constitute the biological sensing element leading to a high operational stability and multiple adaptations to various conditions such as temperature, pH and ionic strength changes. In this work we describe the development of a urea biosensor by immobilizing Proteus mirabilis bacteria onto an insulator-semiconductor electrode on functionalized Fe3O4 nanoparticles (NPs), using cationic, Poly (allylamine hydrochloride) then anionic, Poly (sodium 4-styrenesulfonate) polyelectrolytes, BSA (serum bovin albumin), and glutaraldehyde as a cross-linking agent. The response of P. mirabilis to urea addition is evaluated in homogeneous and heterogeneous phases. Before the immobilization step, the activity of urease produced from the P. mirabilis bacteria was attempted using the ion ammonium selective electrodes (ISEs). Adhesion of the bacteria cells on IS electrodes have been studied using contact angle measurements. After immobilization of the bacteria, on the (Si/SiO2/Si3N4) and (Si/SiO2) substrates, the relationship between the evolution of the flat band potential ∆VFB and the urea concentration is found to be linear for values ranging from 10(-2)M to 10(-5)M.

Topics: Ammonia; Animals; Biosensing Techniques; Cattle; Electrochemical Techniques; Electrodes; Ferrosoferric Oxide; Glutaral; Hydrogen-Ion Concentration; Kinetics; Magnetite Nanoparticles; Polyamines; Proteus mirabilis; Semiconductors; Serum Albumin, Bovine; Silicon; Silicon Compounds; Silicon Dioxide; Urea; Urease

In this paper, a graded SiNx and SiOxNy structure is proposed as antireflection coatings deposited on top of amorphous silicon (α-Si) thin-film solar cell. The structural parameters are optimized by differential evolution in order to enhance the optical absorption of solar cells to the greatest degree. The optimal design result demonstrates that the nonlinear profile of dielectric constant is superior to the linear profile, and discrete multilayer graded antireflection coatings can outperform near continuously graded antireflection coatings. What's more, the electric field intensity distributions clearly demonstrate the proposed graded SiNx and SiOxNy structure can remarkably increase the magnitude of electric field of a-Si:H layer and hence, enhance the light trapping of a-Si:H thin-film solar cells in the whole visible and near-infrared spectrum. Finally, we have compared the optical absorption enhancements of proposed graded SiNx and SiOxNy structure with nanoparticles structure, and demonstrated that it can result in higher enhancements compared to the dielectric SiC and TiO2 nanoparticles. We have shown that the optimal graded SiNx and SiOxNy structure optimized by differential evolution can reach 33.31% enhancement which has exceeded the ideal limit of 32% of nanoparticles structure including plasmonic Ag nanoparticles, dielectric SiC and TiO2 nanoparticles.

Topics: Algorithms; Biomimetics; Computer Simulation; Light; Materials Testing; Models, Statistical; Nanoparticles; Nanotechnology; Optics and Photonics; Oxides; Silicon; Silicon Compounds; Silver; Solar Energy

Multi biomarkers' assays are of great significance in clinical diagnosis. A label-free multi tumor markers' parallel detection system was proposed based on a light addressable potentiometric sensor (LAPS). Arrayed LAPS chips with basic structure of Si(3)N(4)-SiO(2)-Si were prepared on silicon wafers, and the label-free parallel detection system for this component was developed with user friendly controlling interfaces. Then the l-3,4-dihydroxyphenyl-alanine (L-Dopa) hydrochloric solution was used to initiate the surface of LAPS. The L-Dopa immobilization state was investigated by the theoretical calculation. L-Dopa initiated LAPS' chip was biofunctionalized respectively by the antigens and antibodies of four tumor markers, α-fetoprotein (AFP), carcinoembryonic antigen (CEA), cancer antigen 19-9 (CA19-9) and Ferritin. Then unlabeled antibodies and antigens of these four biomarkers were detected by the proposed detection systems. Furthermore physical and measuring principles in this system were described, and qualitative understanding for experimental data were given. The measured response ranges were compared with their clinical cutoff values, and sensitivities were calculated by OriginLab. The results indicate that this bioinitiated LAPS based label-free detection system may offer a new choice for the realization of unlabeled multi tumor markers' clinical assay.

Topics: Biomarkers, Tumor; Biosensing Techniques; Humans; Levodopa; Light; Molecular Conformation; Molecular Dynamics Simulation; Potentiometry; Silicon; Silicon Compounds; Silicon Dioxide; Surface Properties

We demonstrate a reliable microfabrication process for a combined atomic force microscopy (AFM) and scanning electrochemical microscopy (SECM) measurement tool. Integrated cone-shaped sensors with boron doped diamond (BDD) or gold (Au) electrodes were fabricated from commercially available AFM probes. The sensor formation process is based on mature semiconductor processing techniques, including focused ion beam (FIB) machining, and highly selective reactive ion etching (RIE). The fabrication approach preserves the geometry of the original AFM tips resulting in well reproducible nanoscaled sensors. The feasibility and functionality of the fully featured tips are demonstrated by cyclic voltammetry, showing good agreement between the measured and calculated currents of the cone-shaped AFM-SECM electrodes.

Topics: Algorithms; Boron; Chromium; Diamond; Electrochemical Techniques; Electrochemistry; Gold; Microelectrodes; Microscopy, Atomic Force; Microscopy, Electron, Scanning; Microscopy, Scanning Probe; Nanotechnology; Silicon; Silicon Compounds; Spectrometry, X-Ray Emission; Titanium

Single-mode, strip-loaded silicon-rich silicon nitride (SRSN) waveguide with 11 at.% excess Si and 1.7×10(20) cm(-3) Er was fabricated and characterized. By using a 350 nm thick SRSN:Er core layer and a 850 nm wide SiO2 strip, a high core-mode overlap of 0.85 and low transmission loss of 2.9 dB/cm is achieved. Population inversion of 0.73-0.75, close to the theoretical maximum, is estimated to have been achieved via 1480 nm resonant pumping, indicating that nearly all doped Er in SRSN are optically active. Analysis of the pump power dependence of Er3+ luminescence intensity and lifetime indicate that the Er cooperative upconversion coefficient in SRSN:Er is as low as 2.1×10(-18) cm3/sec.

Topics: Equipment Design; Equipment Failure Analysis; Europium; Materials Testing; Refractometry; Silicon; Silicon Compounds

Post-deposition annealing of a-Si/SiN(x) multilayer films at different temperature shows varying shift in high frequency (1 MHz) capacitance-voltage (HFCV) characteristics. Various a-Si/SiN(x) multilayer films were deposited using hot wire chemical vapor deposition (HWCVD) and annealed in the temperature range of 800 to 900 degrees C to precipitate Si quantum dots (Si-QD) in a-Si layers. HFCV measurements of the as-deposited and annealed films in metal-insulator-semiconductor (MIS) structures show hysterisis in C-V curves. The hysteresis in the as-deposited films and annealed films is attributed to charge trapping in Si-dangling bonds in a-Si layer and in Si-QD respectively. The charge trapping density in Si-QD increases with temperature while the interface defects density (D(it)) remains constant.

Topics: Electric Capacitance; Electric Impedance; Gases; Hardness; Hot Temperature; Materials Testing; Nanostructures; Particle Size; Silicon; Silicon Compounds

A new method is presented for the fast and reproducible functionalization of silicon and silicon nitride surfaces coated with covalently attached alkyl monolayers. After formation of a methyl-terminated 1-hexadecyl monolayer on H-terminated Si(100) and Si(111) surfaces, short plasma treatments (1-3 s) are sufficient to create oxidized functionalities without damaging the underlying oxide-free silicon. The new functional groups can, e.g., be derivatized using the reaction of surface aldehyde groups with primary amines to form imine bonds. In this way, plasma-treated monolayers on silicon or silicon nitride surfaces were successfully coated with nanoparticles, or proteins such as avidin. In addition, we demonstrate the possibility of micropatterning, using a soft contact mask during the plasma treatment. Using water contact angle measurements, ellipsometry, XPS, IRRAS, AFM, and reflectometry, proof of principle is demonstrated of a yet unexplored way to form patterned alkyl monolayers on oxide-free silicon surfaces.

Topics: Avidin; Coated Materials, Biocompatible; Microscopy, Atomic Force; Models, Theoretical; Nanoparticles; Oxidation-Reduction; Photoelectron Spectroscopy; Plasma; Silicon; Silicon Compounds; Spectroscopy, Fourier Transform Infrared

A lipid bilayer with gigaohm resistance was fabricated over a single 800 nm pore in a Si3N4 chip using 50 nm liposomes. The nanopore was prefilled with a polyelectrolyte multilayer (PEM) that triggered the spontaneous fusion of the lipid vesicles. Pore-forming peptide melittin was incorporated in the bilayer, and single channel activities were monitored for a period of 2.5 weeks. The long lifetime of the system enabled the observation of the time-dependent stabilization effect of the melittin open state upon bias application.

Topics: Amino Acid Sequence; Electric Impedance; Electrolytes; Lipid Bilayers; Melitten; Molecular Sequence Data; Nanopores; Nanotechnology; Polymers; Porosity; Silicon; Silicon Compounds

We report the design criteria and performance of Si ring resonators for passive athermal applications in wavelength division multiplexing (WDM). The waveguide design rules address i) positive-negative thermo-optic (TO) composite structures, ii) resonant wavelength dependent geometry to achieve constant confinement factor (Gamma), and iii) observation of small residual second order effects. We develop exact design requirements for a temperature dependent resonant wavelength shift (TDWS) of 0 pm/K and present prototype TDWS performance of 0.5 pm/K. We evaluate the materials selection tradeoffs between high-index contrast (HIC) and low-index contrast (LIC) systems and show, remarkably, that FSR and footprint become comparable under the constraint of athermal design.

Topics: Electronics; Hot Temperature; Models, Theoretical; Optics and Photonics; Polymers; Refractometry; Silicon; Silicon Compounds

Visible electroluminescence (EL) with two composite bands, i.e., a violet band and a green-yellow band has been observed from Si-implanted silicon nitride thin films. By varying the intensity ratio of the two composite EL bands in terms of the injection current, strong white-color EL can be achieved at certain injection currents (e.g., ~265 mA/cm(2)). The observed transition in EL color from violet to white under different injection conditions is studied based on the understanding that the violet band is originated from silicon nitride matrix while the green-yellow band is related to the implanted Si. The Si-implanted silicon nitride thin film offers the possibility of electrically tunable white-light Si-based light emitters.

Topics: Color; Electromagnetic Fields; Equipment Design; Equipment Failure Analysis; Lighting; Luminescent Measurements; Membranes, Artificial; Semiconductors; Silicon; Silicon Compounds

It is shown that the resonant frequencies and the transmission spectra of ring resonators can be adjusted by depositing or etching the cladding nitride layer on the ring waveguide without introducing an extra loss or extra variations of channel spacing. The cladding nitride layer increases the minimum width of the gap in the coupling region to larger than 150nm which makes it possible to consider photolithography instead of E-beam lithography for the typical design rule of ring filters. KOH silicon etching can also adjust not only the resonance frequencies but also coupling coefficients with a small sacrifice of guiding loss.

Topics: Algorithms; Equipment Design; Hydroxides; Materials Testing; Models, Statistical; Optics and Photonics; Potassium Compounds; Silicon; Silicon Compounds; Spectrum Analysis, Raman; Temperature; Time Factors

In this work, silicon-rich silicon nitride (SRN) layers were deposited on a silicon wafer by microwave-assisted plasma-enhanced chemical vapor deposition (MW-PECVD) using NH(3) and SiH(4) as precursor gases. The Si excess in the as-deposited layers as determined by the Rutherford backscattering technique was controlled by varying the precursor gas ratio. We were able to produce silicon nanoparticles (Si-nps) in the silicon nitride (SiN(x)) layers upon thermal annealing at high temperature. Energy-filtered TEM (EFTEM), complemented by photoluminescence measurements, were used to identify the experimental parameters in order to reach a high density of well-separated Si-nps (3 nm). Our results show that the MW-PECVD method is a suitable deposition tool for the formation of Si-nps in thin SRN layers.

Topics: Ammonia; Nanoparticles; Nanostructures; Nanotechnology; Silicon; Silicon Compounds

The submillimetre or terahertz region of the electromagnetic spectrum contains approximately half of the total luminosity of the Universe and 98% of all the photons emitted since the Big Bang. This radiation is strongly absorbed in the Earth's atmosphere, so space-based terahertz telescopes are crucial for exploring the evolution of the Universe. Thermal emission from the primary mirrors in these telescopes can be reduced below the level of the cosmic background by active cooling, which expands the range of faint objects that can be observed. However, it will also be necessary to develop bolometers-devices for measuring the energy of electromagnetic radiation-with sensitivities that are at least two orders of magnitude better than the present state of the art. To achieve this sensitivity without sacrificing operating speed, two conditions are required. First, the bolometer should be exceptionally well thermally isolated from the environment; second, its heat capacity should be sufficiently small. Here we demonstrate that these goals can be achieved by building a superconducting hot-electron nanobolometer. Its design eliminates the energy exchange between hot electrons and the leads by blocking electron outdiffusion and photon emission. The thermal conductance between hot electrons and the thermal bath, controlled by electron-phonon interactions, becomes very small at low temperatures ( approximately 1 x 10-16 W K-1 at 40 mK). These devices, with a heat capacity of approximately 1 x 10-19 J K-1, are sufficiently sensitive to detect single terahertz photons in submillimetre astronomy and other applications based on quantum calorimetry and photon counting.

Topics: Astronomy; Electromagnetic Fields; Electrons; Energy Transfer; Equipment Design; Hot Temperature; Nanotechnology; Niobium; Photons; Physics; Piperidones; Polymethyl Methacrylate; Sensitivity and Specificity; Silicon; Silicon Compounds; Silicon Dioxide; Surface Properties; Thermal Conductivity; Titanium

Silicon nitride is the most commonly used passivation layer in biosensor applications where electronic components must be interfaced with ionic solutions. Unfortunately, the predominant method for functionalizing silicon nitride surfaces, silane chemistry, suffers from a lack of reproducibility. As an alternative, we have developed a silane-free pathway that allows for the direct functionalization of silicon nitride through the creation of primary amines formed by exposure to a radio frequency glow discharge plasma fed with humidified air. The aminated surfaces can then be further functionalized by a variety of methods; here we demonstrate using glutaraldehyde as a bifunctional linker to attach a robust NeutrAvidin (NA) protein layer. Optimal amine formation, based on plasma exposure time, was determined by labeling treated surfaces with an amine-specific fluorinated probe and characterizing the coverage using X-ray photoelectron spectroscopy (XPS). XPS and radiolabeling studies also reveal that plasma-modified surfaces, as compared with silane-modified surfaces, result in similar NA surface coverage, but notably better reproducibility.

Topics: Air; Amines; Avidin; Biosensing Techniques; Biotin; Biotinylation; Fluorescent Dyes; Fluorine; Glutaral; Proteins; Reproducibility of Results; Silicon; Silicon Compounds; Spectrometry, X-Ray Emission; Surface Properties

Resorbable silicon stabilized tricalcium phosphate (Si-TCP)-based bioceramics are characterized from a biological perspective by measuring the intermolecular interaction force between osteopontin (OPN) protein and the material surface using atomic force microscopy (AFM). OPN protein was covalently bound to silicon nitride AFM tips and adsorption and adhesion forces were measured in an electrolyte with a composition similar to that of physiological fluids. A strong relationship exists between the adhesion force of OPN on the material surface, the number of adherent osteoclasts (OC) and the resorption of the material. OPN adhesion is strongest on hydroxyapatite (HA) surfaces, or in samples that induce a HA-like surface through a precipitation reaction in electrolytic media. It is proposed that the increased biological response of the Si-TCP phase can be attributed in part to its reactivity in a physiological electrolyte, which involves a rapid conversion to a calcium deficient HA phase with a corresponding increase in the adhesion strength of OPN to the material, with a consequentially higher OC resorption response.

Topics: Adsorption; Animals; Biocompatible Materials; Calcium; Calcium Phosphates; Cell Adhesion; Cell Culture Techniques; Cell Line; Cells, Cultured; Ceramics; Durapatite; Electrolytes; Humans; Kinetics; Mass Spectrometry; Mice; Microscopy, Atomic Force; Models, Chemical; Models, Statistical; Osteoclasts; Osteopontin; Rats; Rats, Wistar; Sialoglycoproteins; Silicon; Silicon Compounds; Surface Properties; Time Factors

A hydrophilic silicon nitride surface was grafted with poly(ethylene glycol) monomethyl ether (average formula weight of 5000 Da) in a one-step protocol. The domains of stable dendritic structures of self-assembled monolayer islands on a silicon nitride surface were observed with atomic force microscopy. The moduli of elasticity of these dendritic structures in air and in KCl aqueous solution were compared. The value of the Young's modulus of these structures is reduced by more than 3 orders of magnitude, from approximately 12 GPa measured in air to approximately 5 MPa in KCl solution. This dramatic reduction in elasticity was attributed to the swelling of the dendritic structures in aqueous solution, which was verified by the increased film thickness. These dendritic structures were not stable in the aqueous environment and could be removed by soaking in water for 22 h because of the hydrolysis of the silicate bonds. This fact was confirmed by the reduction of the C1s signal in the X-ray photoelectron spectroscopy experiments. These morphologies are not unique to silicon nitride substrate; similar features were also observed for thiolated poly(ethylene glycol) monomethyl ether molecules absorbed on a gold surface.

Topics: Adsorption; Chemistry, Physical; Elasticity; Gold; Methyl Ethers; Microscopy, Atomic Force; Models, Chemical; Polyethylene Glycols; Potassium Chloride; Pressure; Silicon; Silicon Compounds; Spectrometry, X-Ray Emission; Sulfhydryl Compounds; Surface Properties

The influence of the surface properties of chemically modified silicon nitride microsieves on the filtration of protein solutions and defatted milk is described in this research. Prior to membrane filtrations, an antifouling polymer based on poly(ethylene glycol), poly(TMSMA-r-PEGMA) was synthesized and applied on silicon-based surfaces like silicon, silicon nitride, and glass. The ability of such coating to repel proteins like bovine serum albumin (BSA) was confirmed by ellipsometry and confocal fluorescence microscopy. In BSA and skimmed milk filtrations no differences could be seen between unmodified and PEG-coated membranes (decreasing permeability in time). On the other hand, reduced fouling was observed with PEG-modified microsieves in combination with backpulsing and air sparging.

Topics: Air Pollutants, Occupational; Glass; Microchemistry; Microscopy, Electron, Scanning; Polyethylene Glycols; Polymethacrylic Acids; Silicon; Silicon Compounds; Surface Properties; Trimethylsilyl Compounds; Water Pollutants

Silicon nitride nanowires synthesized by the pyrolysis of perhydropolysilazane without using any catalysts are reported. After pyrolysis at 1073 K in N2/NH3 atmosphere, the synthetic nanowires are discrete and curly with diameters about tens of nanometers and lengths of hundreds of nanometers. While after post-treatment at 1873 K in N2 atmosphere, the nanowires are continuous and randomly distributed with diameters about tens of nanometers and several microns in length. There are no bulbs or droplets on the tips of the nanowires, and two gas-solid mechanisms are proposed to explain their growth.

Topics: Chemical Fractionation; Crystallization; Electric Wiring; Gases; Hot Temperature; Materials Testing; Molecular Conformation; Nanostructures; Nanotechnology; Nitrogen; Particle Size; Silicon; Silicon Compounds; Surface Properties

Nickel nanocontacts for studying ballistic magnetoresistance have been fabricated by sputtering through FIB prepared nanostencil masks and by using electron beam assisted deposition of SiO2 to reduce the size of FIB milled pores through silicon nitride membranes. These two methods are discussed in terms of the nanocontact sizes, fabrication, and yield. The smallest size of the nanocontacts prepared using the nanostencil method was 40 nm and by the filling method was 1-2 nm. The maximum magnetoresistance measured was 1% and no evidence of a large ballistic magnetoresistance was observed.

Topics: Crystallization; Electrons; Magnetics; Microscopy, Electron, Transmission; Nanoparticles; Nanotechnology; Nickel; Silicon; Silicon Compounds; Silicon Dioxide; Time Factors

Topics: Animals; Cadmium Compounds; Cytophotometry; Light; Mice; Microfluidic Analytical Techniques; Microscopy, Electron, Scanning; Microscopy, Fluorescence; Microspheres; Nanostructures; Nanotechnology; NIH 3T3 Cells; Quantum Dots; Semiconductors; Silicon; Silicon Compounds; Spectrum Analysis; Sulfides

We report on the 3-D modelling of periodic arrays of capacitive micromachined ultrasonic transducers (cMUTs) operating in fluid. Specific developments have been performed to model biperiodic transducer arrays and to take into account radiation into any stratified media at the front-side as well as the back-side of the device. The model is based on a periodic finite-element-analysis/boundary-element-method (FEA/BEM). It is applied to micromachined ultrasonic transducers (MUTs), based on silicon-nitride-circular-membrane arrays on a silicon substrate, and operating in water. The spectrum characteristics of MUTs excited in phase are investigated, showing that very-large-band emission is achievable as previously demonstrated by many authors. However, other contributions are also found, depending on the excitation conditions, that do not radiate in the fluid. These contributions are identified as guided modes that could generate significant cross-talk effects. The origin and the nature of these modes is analyzed to gain insight in the actual operation of MUTs.

Topics: Equipment Design; Finite Element Analysis; Humans; Miniaturization; Periodicity; Silicon; Silicon Compounds; Transducers; Ultrasonography; Water

We have monitored deflection-distance curves with an atomic force microscope (AFM) in contact mode, with a silicon nitride tip, on chemically modified silicon wafers, in the air. The wafers were modified on their surface by grafting self-assembled monolayers (SAMs) of different functional groups such as methyl, ester, amine, or methyl fluoride. A chemically modified surface with a functionalized hydroxyl group was also considered. Qualitative analysis allowed us to compare adhesive forces versus chemical features and surface energy. The systematic calibration procedure of the AFM measurements was performed to produce quantitative data. Our results show that the experimentally determined adhesive force or thermodynamic work of adhesion increases linearly with the total surface energy determined with contact angles measured with different liquids. The influence of capillary condensation of atmospheric water vapor at the tip-sample interface on the measured forces is discussed. Quantitative assessment values were used to determine in situ the SAM-tip thermodynamic work of adhesion on a local scale, which have been found to be in good agreement with quoted values. Finally, the determination of the surface energy of the silicon wafer deduced from the thermodynamic work of adhesion is also proposed and compared with the theoretical value.

Topics: Microscopy, Atomic Force; Silicon; Silicon Compounds; Surface Properties; Thermodynamics

A miniature broadband light source is a critical element in a spectrophotometric microsystem. The design, fabrication, and characterization of a highly stable, miniature broadband light source that comprises filaments of single-crystal silicon are presented. Electrical current versus voltage and radiant emittance spectra under constant voltage bias are measured and related to filament dimensions. A maximum stable operating temperature for these filaments is estimated to be 1200 K. Resistance drift is demonstrated to be less than 0.5% over a 10-h period of continuous operation with visible incandescence. Emittance spectra of a multifilament array, measured at three different electrical biases, are presented and shown to compare well with theoretical blackbody radiation spectra. A continuous, total radiated power of 10.7 mW was achieved with a 1 mm x 1 mm filament array with peak emittance at lambda=2.7 micrometers.

Topics: Hot Temperature; Infrared Rays; Light; Miniaturization; Silicon; Silicon Compounds; Spectrophotometry, Infrared; Time Factors

Medical devices based on microelectro-mechanical systems (MEMS) platforms are currently being proposed for a wide variety of implantable applications. However, biocompatibility data for typical MEMS materials of construction and processing, obtained from standard tests currently recognized by regulatory agencies, has not been published. Likewise, the effects of common sterilization techniques on MEMS material properties have not been reported. Medical device regulatory requirements dictate that materials that are biocompatibility tested be processed and sterilized in a manner equivalent to the final production device. Material, processing, and sterilization method can impact the final result. Six candidate materials for implantable MEMS devices, and one encapsulating material, were fabricated using typical MEMS processing techniques and sterilized. All seven materials were evaluated using a baseline battery of ISO 10993 physicochemical and biocompatibility tests. In addition, samples of these materials were evaluated using a scanning electron microscope (SEM) pre- and post-sterilization. While not addressing all facets of ISO 10993 testing, the biocompatibility and SEM data indicate few concerns about use of these materials in implant applications.

Topics: Biocompatible Materials; Bone Substitutes; Carbon Compounds, Inorganic; Materials Testing; Microscopy, Electron, Scanning; Silicon; Silicon Compounds; Silicon Dioxide; Time Factors; Titanium; Water

Room temperature photoluminescence (PL) with a peak at 1.54 microns was observed from silicon oxide, silicon-rich silicon oxide, silicon nitride and silicon-rich silicon nitride films, all doped with Er and grown by the magnetron sputtering technique. To determine the optimum annealing temperature for the 1.54 microns PL, these films were annealed in the range of 600-1,100 degrees C with an interval of 100 degrees C. Among these four types of films annealed at an identical temperature, the intensity of 1.54 microns PL peak of the Er-doped silicon-rich silicon oxide film was always the strongest one, which arrived at a maximum in 800 degrees C annealing. A 1.38 microns PL band was also observed in each of these four types of films, and which in the silicon-rich silicon oxide or silicon-rich silicon nitride films was found to be correlated with the 1.54 microns PL band in intensity.

Topics: Chemical Phenomena; Chemistry, Physical; Erbium; Luminescence; Nanotechnology; Oxides; Silicon; Silicon Compounds; Temperature

For alpha-quartz, monoclinic ZSM-5, alpha- and beta-Si3N4 and SiC-6H polytype, the silicon chemical shifts have been calculated using the IGLO (individual gauge for localized orbitals) method and models of different size in real crystal geometry. The result is a theoretical chemical shift scale, which is very similar to the corresponding experimental scale from 29Si MAS NMR experiments. It is shown that the assignment of isotropic silicon chemical shifts of crystallized solids based on theory is a method of practical applicability, also in cases where experimental methods or empirical relations fail. The two NMR spectral lines of alpha-Si3N4 are for the first time assigned to the crystallographic positions. The partition of the silicon chemical shifts into localized contributions from different parts of the model allows insight into the interactions around the resonance nucleus due to substituent and geometry variations leading to silicon chemical shifts.

Topics: Carbon Compounds, Inorganic; Ceramics; Isotopes; Magnetic Resonance Spectroscopy; Silicon; Silicon Compounds; Silicon Dioxide

The microreaction volumes of PCR chips (a microfabricated silicon chip bonded to a piece of flat glass to form a PCR reaction chamber) create a relatively high surface to volume ratio that increases the significance of the surface chemistry in the polymerase chain reaction (PCR). We investigated several surface passivations in an attempt to identify 'PCR friendly' surfaces and used those surfaces to obtain amplifications comparable with those obtained in conventional PCR amplification systems using polyethylene tubes. Surface passivations by a silanization procedure followed by a coating of a selected protein or polynucleotide and the deposition of a nitride or oxide layer onto the silicon surface were investigated. Native silicon was found to be an inhibitor of PCR and amplification in an untreated PCR chip (i.e. native slicon) had a high failure rate. A silicon nitride (Si(3)N(4) reaction surface also resulted in consistent inhibition of PCR. Passivating the PCR chip using a silanizing agent followed by a polymer treatment resulted in good amplification. However, amplification yields were inconsistent and were not always comparable with PCR in a conventional tube. An oxidized silicon (SiO(2) surface gave consistent amplifications comparable with reactions performed in a conventional PCR tube.

Topics: Base Sequence; Glass; Molecular Sequence Data; Polymerase Chain Reaction; Polymers; Silicon; Silicon Compounds; Silicon Dioxide

Additions of paramagnetic lanthanides are found to increase the relaxation rates of both 89Y and 29Si in the yttrium silicon oxynitride compounds Y2Si3N4O3 (N-melilite) and Y4Si2O7N2 (J-phase), allowing the observation of previously unreported 89Y magic-angle spinning nuclear magnetic resonance spectra of these phases. The dependence of the 89Y and 29Si relaxation rates was determined as a function of Yb3+ and Gd3+ concentration. Both the 29Si and 89Y resonances become broader with increasing Yb concentration, but at all lanthanide concentrations the 89Y spectrum of J-phase is broader than that of N-melilite, possibly due to a greater distribution of Y site geometries in the former. At concentrations below about 360 mumol g-1, the lanthanide ions appear to be incorporated in the lattice, but are not involved in covalent bonding to Y or Si. The effect of a series of lanthanides on the 89Y and 29Si relaxation rates and line widths is presented in terms of the lanthanide spin quantum numbers and magnetic moments. The most effective lanthanide was found to be Eu3+, giving fast relaxation (particularly for 89Y) and sharp lines.

Topics: Air Pollutants, Occupational; Magnetic Resonance Spectroscopy; Metals, Rare Earth; Silicon; Silicon Compounds; Yttrium

Topics: Electron Probe Microanalysis; Indium; Microscopy, Electron, Scanning; Silicon; Silicon Compounds; Tin; Tin Compounds

Using a mix of thermal and anodic bonding together with microlithographic techniques, the safe transference of a Si3N4 film with a pore (diameter down to 1 micron) to a glass tube tip (external diameter 800 microns) was accomplished, yielding a new geometrical form of micropipette. Compared with conventional glass micropipettes the device has shown lower resistance, more stable capacitance (independent of the tip immersion depth), tip potential closer to that of a salt bridge, and a simplified filling process. Using this device as a potassium ion selective electrode (ISE), a faster response time ISE was achieved. These features indicate that the new device can advantageously substitute the conventional glass micropipettes when cell impalement is not required.

Topics: Electric Conductivity; Equipment Design; Evaluation Studies as Topic; Ions; Microelectrodes; Micromanipulation; Potassium; Silicon; Silicon Compounds

A new system has been developed for determining the deformability of individual red blood cells (RBCs), simulating the passage of RBCs in capillaries. The kernel of this system was the micropore array filter with an accurately defined pattern made by semiconductor microprocessing techniques. Individual microscopic RBC images were processed in parallel through a microcomputer and its interfacing circuit. An experiment with a normal RBC from a human donor demonstrated that it could pass the circular pore filter with a diameter as small as 1.0 micron at 2 cm H2O pressure difference. Deformability of RBCs treated with diamide or acetylphenylhidralazine was also measured, showing that the system was sufficiently sensitive to detect the deformability loss due to membrane damage or to polymerization of the cytoplasma.

Topics: Adult; Erythrocyte Deformability; Humans; Membranes, Artificial; Microscopy, Electron, Scanning; Silicon; Silicon Compounds; Time Factors

To measure the concentrations of yttrium-oxide-coated small-dispersed silicon nitride plasma powder, the air was aspirated at the amount of 10-15 litres per min through the AFA-XP filter. The filter was limed in a platinum crucible, the residuum being alloyed with Na2CO3, Na2B4O7, NaNO3 in ratio 10:5:1. The alloy was transferred into solution in which the silicon content was assessed through reactions with ammonium molybdate, and yttrium--through reactions with arsenaso III. The sensibility rate for silicon was at 0.07 mg/m3.

Topics: Air Pollutants, Occupational; Chemical Industry; Filtration; Humans; Maximum Allowable Concentration; Photometry; Silicon; Silicon Compounds; USSR; Yttrium

Developments and use of man-made mineral fibres are important for the progress in some technical fields. In the last years the number of man-made mineral fibres increased extraordinarily. For the medical evaluation it is necessary to determine the physico-chemical characteristics of the man-made mineral fibre dust and its biological effects in animal experiments. The results of the investigations are described.

Topics: Animals; Ceramics; Dust; Rats; Rats, Inbred Strains; Respiratory System; Silicon; Silicon Compounds; Spectrum Analysis

Topics: Animals; Bone and Bones; Ceramics; Materials Testing; Rabbits; Silicon; Silicon Compounds

Bovine pulmonary macrophages were exposed in vitro to 0.3, 0.1, 0.03, or 0.01 mg/ml of a fibrous silicon nitride, nonfibrous (milled) silicon nitride comminuted from the fibrous powder, alpha-quartz (an active control), or glass beads (an inert control). Functional evaluation of the exposed cells indicated that the fibrous silicon nitride was as cytotoxic as quartz, while the nonfibrous silicon nitride was relatively inert. To further evaluate the mechanisms of cytotoxicity, the cells were exposed to 1 mg/ml of the control and test materials and biochemical studies were performed. Quartz increased release of both the cytoplasmic enzyme, lactate dehydrogenase (LDH), and the lysosomal enzyme, acid phosphatase (AP), consistent with both cell membrane and lysosome lysis. In addition, total protein levels were significantly depressed, suggesting significant impairment of cellular synthetic processes. LDH, but not AP, values were increased with fibrous silicon nitride treatment, but not with the nonfibrous silicon nitride. In contrast to quartz, which increased LDH levels by 65%, the fibrous silicon nitride only increased LDH levels by 11%. Scanning electron micrographs further indicated that the fibrous silicon is cytotoxic and poorly tolerated by macrophages. These studies provide further evidence of morphology as a primary determinant of cytotoxicity since the milled powder test article was comminuted from the fibrous material.

Topics: Acid Phosphatase; Animals; Cattle; Cell Adhesion; Endocytosis; L-Lactate Dehydrogenase; Macrophages; Microscopy, Electron, Scanning; Phagocytosis; Proteins; Pulmonary Alveoli; Silicon; Silicon Compounds; Trypan Blue

This article presents a morphologic assessment of the effect of silicon nitride ceramic (Si3N4) on rabbit marrow stromal cells and their differentiation when grown in vitro and in vivo. In vitro marrow stromal cells (MSC) attached initially to upper portions of ceramic discs. However, at four weeks, cells only attached to disc edges. Fresh marrow or first passage MSC, inoculated into diffusion chambers with and without Si3N4, formed cartilage, bone, and fibrous tissue after being implanted intraperitoneally for five weeks. Tissue differentiated adjacent to Si3N4 but not within the pores. In contrast, Si3N4 implants inserted into femoral marrow cavities were surrounded initially by woven bone and within three months by mature bone that had permeated implants with a pore size of 255 +/- 64 microns. Plugs having a pore diameter of 170 +/- 45 microns mainly contained vascularized fibrous tissue with occasional foci of osteoid or bone in the peripheral pores. In a pilot experiment, three femoral segmental Si3N4 endoprostheses were implanted in three adult rabbits, and the osseous reactions were monitored during their natural life. Each implant was enclosed by a stable cuff of bone within four months of implantation and remained unchanged during the rest of the animal's life. Autopsies confirmed these roentgenographic observations, and tissue appositional to each prosthesis was morphologically normal. Si3N4 has the potential of an important ceramic for use in osseous reconstruction.

Topics: Animals; Biocompatible Materials; Bone and Bones; Bone Marrow; Cell Differentiation; Cells, Cultured; Materials Testing; Osteogenesis; Prostheses and Implants; Rabbits; Silicon; Silicon Compounds

The substantial increases in the filler volume fraction of the current generation of composite resins, and the incorporation of radiopacifying heavy elements in many of these fillers, constitute significant changes which may affect thermal transport properties. Thermal diffusivity has been determined for 21 of these composite materials recommended for anterior and posterior applications. For radiopaque hybrid and for microfine composites, there was, however, only a gradual trend to increased thermal diffusivity with increasing volume fraction of inorganic filler. The diffusivity values were not greatly in excess of the level observed for dentin. Nevertheless, a small group of materials, incorporating substantial amounts of quartz or silicon nitride filler particles, exhibited high rates of thermal diffusion, up to three times the level exhibited by dentin.

Topics: Composite Resins; Glass; Materials Testing; Quartz; Silicon; Silicon Compounds; Silicon Dioxide; Thermal Conductivity; Water

Transmission electron microscopy has been used to isolate and examine the intergranular glass phase in hot-pressed silicon nitride/silicon carbide composites. Previously there have been difficulties in locating a suitable region for studies of this nature because the interfering nitride and carbide grains inhibit isolation of the glass for examination. Radiofrequency plasma etching of thinned sections of 6 wt% Y2O3, 2 wt% A12O3 in Si3N4 containing 30 vol% of SiC proved to be fruitful in isolating the glass phase. A mixture of CF4 and O2 quantitatively remove the acicular nitride phase without any evidence of attack on either the glass or carbide. Composites containing ceria and magnesia as substitutes for yttria behave similarly. This indicates that glasses containing minor to major concentrations of elements forming stable fluorides inhibit the attack of fluoride ions on silica glasses containing these elements.

Topics: Carbon; Carbon Compounds, Inorganic; Microscopy, Electron; Microscopy, Electron, Scanning; Silicon; Silicon Compounds

Topics: Electrodes, Implanted; Electroencephalography; Humans; Membranes, Artificial; Silicon; Silicon Compounds