Tungsten disilicide (WSi₂) is an inorganic compound, a

silicide A silicide is a type of chemical compound that combines silicon and a usually more electropositive element. Silicon is more electropositive than carbon. In terms of their physical properties, silicides are structurally closer to borides than t ...

tungsten Tungsten (also called wolfram) is a chemical element; it has symbol W and atomic number 74. It is a metal found naturally on Earth almost exclusively in compounds with other elements. It was identified as a distinct element in 1781 and first ...

. It is an electrically conductive

ceramic A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcela ...

material.

Chemistry

Tungsten disilicide can react violently with substances such as

strong acid Acid strength is the tendency of an acid, symbolised by the chemical formula , to dissociate into a hydron (chemistry), proton, , and an anion, . The Dissociation (chemistry), dissociation or ionization of a strong acid in solution is effectivel ...

fluorine Fluorine is a chemical element; it has Chemical symbol, symbol F and atomic number 9. It is the lightest halogen and exists at Standard temperature and pressure, standard conditions as pale yellow Diatomic molecule, diatomic gas. Fluorine is extre ...

oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ''electron donor''). In ot ...

s, and

interhalogen In chemistry, an interhalogen compound is a molecule which contains two or more different halogen atoms (fluorine, chlorine, bromine, iodine, or astatine) and no atoms of elements from any other group. Most interhalogen compounds known are binar ...

Applications

It is used in

microelectronics Microelectronics is a subfield of electronics. As the name suggests, microelectronics relates to the study and manufacture (or microfabrication) of very small electronic designs and components. Usually, but not always, this means micrometre ...

as a contact material, with

resistivity Electrical resistivity (also called volume resistivity or specific electrical resistance) is a fundamental specific property of a material that measures its electrical resistance or how strongly it resists electric current. A low resistivity i ...

60–80 μΩ cm; it forms at 1000 °C. It is often used as a shunt over

polysilicon Polycrystalline silicon, or multicrystalline silicon, also called polysilicon, poly-Si, or mc-Si, is a high purity, polycrystalline form of silicon, used as a raw material by the solar photovoltaic and electronics industry. Polysilicon is produ ...

lines to increase their conductivity and increase signal speed. Tungsten disilicide layers can be prepared by

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 (electro ...

, e.g. using

monosilane Silane (Silicane) is an inorganic compound with chemical formula . It is a colorless, pyrophoric gas with a sharp, repulsive, pungent smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental sil ...

dichlorosilane Dichlorosilane, or DCS as it is commonly known, is a chemical compound with the formula H2SiCl2. In its major use, it is mixed with ammonia (NH3) in LPCVD chambers to grow silicon nitride in semiconductor processing. A higher concentration of DC ...

with

tungsten hexafluoride Tungsten(VI) fluoride, also known as tungsten hexafluoride, is an inorganic compound with the formula . It is a toxic, corrosive, colorless gas, with a density of about (roughly 11 times heavier than air). It is the densest known gas under stand ...

as source gases. The deposited film is non-

stoichiometric Stoichiometry () is the relationships between the masses of reactants and products before, during, and following chemical reactions. Stoichiometry is based on the law of conservation of mass; the total mass of reactants must equal the total m ...

, and requires annealing to convert to more conductive stoichiometric form. Tungsten disilicide is a replacement for earlier tungsten films. Tungsten disilicide is also used as a

barrier layer A diffusion barrier is a thin layer (usually micrometres thick) of metal usually placed between two other metals. It is done to act as a barrier to protect either one of the metals from corrupting the other. Adhesion of a plated metal layer to i ...

between silicon and other metals, e.g. tungsten. Tungsten disilicide is also of value towards use in

microelectromechanical systems MEMS (micro-electromechanical systems) is the technology of microscopic devices incorporating both electronic and moving parts. MEMS are made up of components between 1 and 100 micrometres in size (i.e., 0.001 to 0.1 mm), and MEMS devices ...

, where it is mostly applied as thin films for fabrication of microscale circuits. For such purposes, films of tungsten disilicide can be plasma-etched using e.g.

nitrogen trifluoride Nitrogen trifluoride is the inorganic compound with the formula (). It is a colorless, non-flammable, toxic gas with a slightly musty odor. In contrast with ammonia, it is nonbasic. It finds increasing use within the manufacturing of flat-panel ...

gas. WSi₂ performs well in applications as

oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

-resistant coatings. In particular, in similarity to

Molybdenum disilicide Molybdenum disilicide (MoSi2, or molybdenum silicide), an intermetallic compound, a silicide of molybdenum, is a refractory ceramic with primary use in heating elements. It has moderate density, melting point 2030 °C, and is electrically ...

, MoSi₂, the high

emissivity The emissivity of the surface of a material is its effectiveness in emitting energy as thermal radiation. Thermal radiation is electromagnetic radiation that most commonly includes both visible radiation (light) and infrared radiation, which is n ...

of tungsten disilicide makes this material attractive for high temperature

radiative cooling In the study of heat transfer, radiative cooling is the process by which a body loses heat by thermal radiation. As Planck's law describes, every physical body spontaneously and continuously emits electromagnetic radiation. Radiative cooling has b ...

, with implications in

heat shield In engineering, a heat shield is a component designed to protect an object or a human operator from being burnt or overheated by dissipating, reflecting, and/or absorbing heat. The term is most often used in reference to exhaust heat management a ...

s.High emissivity coatings on fibrous ceramics for reusable space systems
Corrosion Science 2019

References

{{Silicides Ceramic materials Group 6 silicides Refractory materials Semiconductor materials Tungsten compounds