A silicide is a compound that has silicon with (usually) more electropositive elements.
Silicon is more electropositive than carbon. Silicides are structurally closer to borides than to carbides.
Similar to borides and carbides, the composition of silicides cannot be easily specified as covalent molecules. The chemical bonds in silicides range from conductive metal-like structures to covalent or ionic. Silicides of all non-transition metals, with exception of beryllium, have been described.
Silicon atoms in silicides can have many possible organizations:
A silicide prepared by a self-aligned process is called a salicide. This is a process in which silicide contacts are formed only in those areas in which deposited metal (which after annealing becomes a metal component of the silicide) is in direct contact with silicon, hence, the process is self-aligned. It is commonly implemented in MOS/CMOS processes for ohmic contacts of the source, drain, and poly-Si gate..
Group 1 and 2 silicides e.g. Na2Si and Ca2Si react with water, yielding hydrogen and/or silanes. At Consumer Electronics Show (CES) 2012 a safe and eco-friendly 1kWh or 3kWh capacity mobile phone charger with sodium silicide that runs on water has introduced for 'people who spend time away from the electricity grid'. Any type of water can be used, including salt water and it can even run on puddle water providing it isn't thickened with mud or any other sediment.
When magnesium silicide is placed into hydrochloric acid, HCl(aq), the gas silane, SiH4, is produced. This gas is the silicon analogue of methane, CH4, but is more reactive. Silane is pyrophoric, that is, due to the presence of oxygen, it spontaneously combusts in air:
These reactions are typical of a Group 2 silicide. Mg2Si reacts similarly with sulfuric acid. Group 1 silicides are even more reactive. For example, sodium silicide, Na2Si, reacts rapidly with water to yield sodium silicate, Na2SiO3, and hydrogen gas. Rubidium silicide is pyrophoric, igniting in contact with air.
The transition metal silicides are, in contrast, usually inert to aqueous solutions of everything with exception of hydrofluoric acid; however, they react with more aggressive agents, e.g. melted potassium hydroxide, or fluorine and chlorine when red-hot.
Mercury, thallium, bismuth, and lead are immiscible with liquid silicon.
In chemistry, a carbide usually describes a compound composed of carbon and a metal. In metallurgy, carbiding or carburizing is the process for producing carbide coatings on a metal piece.
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard and brittle crystalline solid with a blue-grey metallic lustre; and it is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic table: carbon is above it; and germanium, tin, and lead are below it. It is relatively unreactive. Because of its high chemical affinity for oxygen, it was not until 1823 that Jöns Jakob Berzelius was first able to prepare it and characterize it in pure form. Its melting and boiling points of 1414 °C and 3265 °C respectively are the second-highest among all the metalloids and nonmetals, being only surpassed by boron. Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure element in the Earth's crust. It is most widely distributed in dusts, sands, planetoids, and planets as various forms of silicon dioxide (silica) or silicates. More than 90% of the Earth's crust is composed of silicate minerals, making silicon the second most abundant element in the Earth's crust after oxygen.
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula SiO2, most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing as a compound of several minerals and as synthetic product. Notable examples include fused quartz, fumed silica, silica gel, and aerogels. It is used in structural materials, microelectronics (as an electrical insulator), and as components in the food and pharmaceutical industries.
Silane is an inorganic compound with chemical formula, SiH4, making it a group 14 hydride. It is a colourless, pyrophoric, toxic gas with a sharp, repulsive smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental silicon.
Silicon tetrachloride or tetrachlorosilane is the inorganic compound with the formula SiCl4. It is a colourless volatile liquid that fumes in air. It is used to produce high purity silicon and silica for commercial applications.
Iron(III) chloride is the inorganic compound with the formula. Also called ferric chloride, it is a common compound of iron in the +3 oxidation state. The anhydrous compound is a crystalline solid with a melting point of 307.6 °C. The color depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red.
In chemistry, neutralization or neutralisation is a chemical reaction in which an acid and a base react quantitatively with each other. In a reaction in water, neutralization results in there being no excess of hydrogen or hydroxide ions present in the solution. The pH of the neutralized solution depends on the acid strength of the reactants.
Acidic oxides, or acid anhydride, are oxides that react with water to form an acid, or with a base to form a salt. They are oxides of either nonmetals or of metals in high oxidation states. Their chemistry can be systematically understood by taking an oxoacid and removing water from it, until only an oxide remains. The resulting oxide belongs to this group of substances. For example, sulfurous acid (SO2), sulfuric acid (SO3), and carbonic acid (CO2) are acidic oxides. An inorganic anhydride (a somewhat archaic term) is an acid anhydride without an organic moiety.
A single-displacement reaction, is a chemical reaction in which one element(s) replaces an/other element(s) in a compound. It can be represented generically as:
Magnesium silicide, Mg2Si, is an inorganic compound consisting of magnesium and silicon. As-grown Mg2Si usually forms black crystals; they are semiconductors with n-type conductivity and have potential applications in thermoelectric generators.
Beryllium nitride, Be3N2, is a nitride of beryllium. It can be prepared from the elements at high temperature (1100–1500 °C), unlike Beryllium azide or BeN6, it decomposes in vacuum into beryllium and nitrogen. It is readily hydrolysed forming beryllium hydroxide and ammonia. It has two polymorphic forms cubic α-Be3N2 with a defect anti-fluorite structure, and hexagonal β-Be3N2. It reacts with silicon nitride, Si3N4 in a stream of ammonia at 1800–1900 °C to form BeSiN2.
A strong electrolyte is a solution/solute that completely, or almost completely, ionizes or dissociates in a solution. These ions are good conductors of electric current in the solution.
A salt metathesis reaction, sometimes called a double replacement reaction, double displacement reaction, is a chemical process involving the exchange of bonds between two non-reacting chemical species which results in the creation of products with similar or identical bonding affiliations. This reaction is represented by the general scheme:
Kipp's apparatus, also called Kipp generator, is an apparatus designed for preparation of small volumes of gases. It was invented around 1844 by the Dutch pharmacist Petrus Jacobus Kipp and widely used in chemical laboratories and for demonstrations in schools into the second half of the 20th century.
Disilane is a chemical compound with chemical formula Si2H6 that was identified in 1902 by Henri Moissan and Samuel Smiles (1877–1953). Moissan and Smiles reported disilane as being among the products formed by the action of dilute acids on metal silicides. Although these reactions had been previously investigated by Friedrich Woehler and Heinrich Buff between 1857 and 1858, Moissan and Smiles were the first to explicitly identify disilane. They referred to disilane as silicoethane. Higher members of the homologous series SinH2n+2 formed in these reactions were subsequently identified by Carl Somiesky (sometimes spelled "Karl Somieski") and Alfred Stock.
Methyltrichlorosilane, also known as trichloromethylsilane, is an organosilicon compound with the formula CH3SiCl3. It is a colorless liquid with a sharp odor similar to that of hydrochloric acid. As methyltrichlorosilane is a reactive compound, it is mainly used a precursor for forming various cross-linked siloxane polymers.
Binary compounds of silicon are binary chemical compounds containing silicon and one other chemical element. Technically the term silicide is reserved for any compounds containing silicon bonded to a more electropositive element. Binary silicon compounds can be grouped into several classes. Saltlike silicides are formed with the electropositive s-block metals. Covalent silicides and silicon compounds occur with hydrogen and the elements in groups 10 to 17.
Polysilicon hydrides are polymers containing only silicon and hydrogen. They have the formula where 0.2 ≤ n ≤ 2.5 and x is the number of monomer units. The polysilicon hydrides are generally colorless or pale-yellow/ocher powders that are easily hydrolyzed and ignite readily in air. The surfaces of silicon prepared by MOCVD using silane (SiH4) consist of a polysilicon hydride.
Protonolysis is the cleavage of a chemical bond by acids. Many examples are found in organometallic chemistry since the reaction requires polar Mδ+-Rδ- bonds, where δ+ and δ- signify partial positive and negative charges associated with the bonding atoms. When compounds containing these bonds are treated with acid (HX), these bonds cleave:
Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.