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Rhenium Diselenide
Rhenium diselenide is an inorganic compound with the formula ReSe2. It has a layered structure where atoms are strongly bonded within each layer. The layers are held together by weak Van der Waals force, Van der Waals bonds, and can be easily peeled off from the bulk material. Synthesis Rhenium diselenide with a thickness as small as a triple-atomic layer can be produced by chemical vapor deposition at ambient pressure. A mixture of Ar and hydrogen gases is flown through a tube whose ends are kept at different temperatures. The substrate and Rhenium trioxide, ReO3 powder are placed at the hot end which is heated to 750 °C, and selenium powder is located at the cold end which is kept at 250 °C. :2 ReO3 + 7 Se → 2 ReSe2 + 3 SeO2 Properties As most other dichalcogenides of transition metals, rhenium diselenide has a layered structure where atoms are strongly bonded within each layer and the layers are held together by weak Van der Waals force, Van der Waals bonds. However, whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scanning Electron Microscopy
A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the surface topography and composition. The electron beam is scanned in a raster scan pattern, and the position of the beam is combined with the Intensity (physics), intensity of the detected signal to produce an image. In the most common SEM mode, secondary electrons emitted by atoms excited by the electron beam are detected using a secondary electron detector (Everhart–Thornley detector). The number of secondary electrons that can be detected, and thus the signal intensity, depends, among other things, on specimen topography. Some SEMs can achieve resolutions better than 1 Nanometre, nanometer. Specimens are observed in high vacuum in a Convention (norm), conventional SEM, or in low vacuum or wet conditions in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenides
A selenide is a chemical compound containing a selenium with oxidation number of −2. Similar to sulfide, selenides occur both as inorganic compounds and as organic derivatives, which are called organoselenium compound. Inorganic selenides The parent inorganic selenide is hydrogen selenide (H2Se). It is a colorless, malodorous, toxic gas. It dissolves in aqueous solution, to give the hydrogenselenide or biselenide ion HSe−. At higher pH, selenide forms. Solutions of hydrogen selenide and selenide are oxidized by air to give elemental selenium: : Most elements form selenides. They sometimes have salt-like properties, e.g. sodium selenide, but most exhibit covalent bonding, e.g. molybdenum diselenide. Their properties are diverse, mirroring the diverse properties of the corresponding sulfides. As indicated by the fact that only a few thousand tons of selenium are produced annually, the subset of selenium compounds called selenides find few applications. Commercially s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhenium(IV) Compounds
Rhenium is a chemical element; it has symbol Re and atomic number 75. It is a silvery-gray, heavy, third-row transition metal in group 7 of the periodic table. With an estimated average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust. It has one of the highest melting and boiling points of any element. It resembles manganese and technetium chemically and is mainly obtained as a by-product of the extraction and refinement of molybdenum and copper ores. It shows in its compounds a wide variety of oxidation states ranging from −1 to +7. Rhenium was originally discovered in 1908 by Masataka Ogawa, but he mistakenly assigned it as element 43 (now known as technetium) rather than element 75 and named it ''nipponium''. It was rediscovered in 1925 by Walter Noddack, Ida Tacke and Otto Berg, who gave it its present name. It was named after the river Rhine in Europe, from which the earliest samples had been obtained and worked commer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenium
Selenium is a chemical element; it has symbol (chemistry), symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elemental state or as pure ore compounds in Earth's crust. Selenium ( ) was discovered in 1817 by , who noted the similarity of the new element to the previously discovered tellurium (named for the Earth). Selenium is found in :Sulfide minerals, metal sulfide ores, where it substitutes for sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores. Minerals that are pure selenide or selenate compounds are rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells. Applications in electronics, once important, have been mostly replaced with silicon semiconductor devices. Selenium is still used in a few types of Direct current, DC power surge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhenium Trioxide
Rhenium trioxide or rhenium(VI) oxide is an inorganic compound with the formula ReO3. It is a red solid with a metallic lustre that resembles copper in appearance. It is the only stable trioxide of the Group 7 elements ( Mn, Tc, Re). Preparation and structure Rhenium trioxide can be formed by reducing rhenium(VII) oxide with carbon monoxide at 200 °C or elemental rhenium at 400 °C. :Re2O7 + CO → 2 ReO3 + CO2 :3 Re2O7 + Re → 7 ReO3 Re2O7 can also be reduced with dioxane. Rhenium trioxide crystallizes with a primitive cubic unit cell, with a lattice parameter of 3.742 Å (374.2 pm). The structure of ReO3 is similar to that of perovskite (ABO3), without the large A cation at the centre of the unit cell. Each rhenium center is surrounded by an octahedron defined by six oxygen centers. These octahedra share corners to form the 3-dimensional structure. The coordination number of O is 2, because each oxygen atom has 2 neighbouring Re atoms., p. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Vapor Deposition
Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high-quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films. In typical CVD, the wafer (electronics), wafer (substrate) is exposed to one or more Volatility (chemistry), volatile wikt:precursor, precursors, which chemical reaction, react and/or chemical decomposition, decompose on the substrate surface to produce the desired deposit. Frequently, volatile by-products are also produced, which are removed by gas flow through the reaction chamber. Microfabrication processes widely use CVD to deposit materials in various forms, including: Single crystal, monocrystalline, polycrystalline, amorphous, and Epitaxy, epitaxial. These materials include: silicon (Silicon dioxide, dioxide, silicon carbide, carbide, silicon nitride, nitride, silicon oxynitride, oxynitride), carbon (carbon (fiber), fiber, carbon nanofibers, nanofibers, carbon nanot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Van Der Waals Force
In molecular physics and chemistry, the van der Waals force (sometimes van der Waals' force) is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical electronic bond; they are comparatively weak and therefore more susceptible to disturbance. The van der Waals force quickly vanishes at longer distances between interacting molecules. Named after Dutch physicist Johannes Diderik van der Waals, the van der Waals force plays a fundamental role in fields as diverse as supramolecular chemistry, structural biology, polymer science, nanotechnology, surface science, and condensed matter physics. It also underlies many properties of organic compounds and molecular solids, including their solubility in polar and non-polar media. If no other force is present, the distance between atoms at which the force becomes repulsive rather than attractive as the atoms approach one another is called the van der ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triclinic
class=skin-invert-image, 180px, Triclinic (a ≠ b ≠ c ≠ a and α, β, γ, 90° pairwise different) In crystallography, the triclinic (or anorthic) crystal system is one of the seven crystal systems. A crystal system is described by three basis vectors. In the triclinic system, the crystal is described by vectors of unequal length, as in the orthorhombic system. In addition, the angles between these vectors must all be different and may not include 90°. The triclinic lattice is the least symmetric of the 14 three-dimensional Bravais lattices. It has (itself) the minimum symmetry all lattices have: points of inversion at each lattice point and at 7 more points for each lattice point: at the midpoints of the edges and the faces, and at the center points. It is the only lattice type that itself has no mirror planes. Crystal classes The triclinic crystal system class names, examples, Schönflies notation, Hermann-Mauguin notation, point groups, International Tables for C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inorganic Compound
An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bondsthat is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorganic compounds comprise most of the Earth's crust, although the compositions of the deep Mantle (geology), mantle remain active areas of investigation. All allotropes (structurally different pure forms of an element) and some simple carbon compounds are often considered inorganic. Examples include the allotropes of carbon (graphite, diamond, buckminsterfullerene, graphene, etc.), carbon monoxide , carbon dioxide , carbides, and salt (chemistry), salts of inorganic anions such as carbonates, cyanides, cyanates, thiocyanates, isothiocyanates, etc. Many of these are normal parts of mostly organic systems, including organisms; describing a chemical as inorganic does not necessarily mean that it cannot occur within life, living things. History ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manganese Diselenide
Manganese diselenide is the inorganic compound with the formula MnSe2. This rarely encountered solid is structurally similar to that of iron pyrite (FeS2). Analogous to the description of iron pyrite, manganese diselenide is sometimes viewed as being composed of Mn2+ and Se22− ions, although being a semiconductor, MnSe2 is not appropriately described in formal oxidation states. Spectroscopy The high‐resolution Mn 2p spectra of the MnSe2 has two distinct peaks at 642.2 and 653.9 electronvolt In physics, an electronvolt (symbol eV), also written electron-volt and electron volt, is the measure of an amount of kinetic energy gained by a single electron accelerating through an Voltage, electric potential difference of one volt in vacuum ...s correspond to the Mn 2p3/2 and Mn 2p1/2 spin–orbit components, respectively. The energy difference (Δ 2p) of 11.7 eV confirms the presence of Mn4+ ions in the sample. A good correlation was observed with the literature va ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
