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Antimony Telluride
Antimony telluride is an inorganic compound with the chemical formula Sb2Te3. As is true of other pnictogen chalcogenide layered materials, it is a grey crystalline solid with layered structure. Layers consist of two atomic sheets of antimony and three atomic sheets of tellurium and are held together by weak van der Waals forces. Sb2Te3 is a narrow-gap semiconductor with a band gap 0.21 eV; it is also a topological insulator, and thus exhibits thickness-dependent physical properties. Crystalline structure Sb2Te3 has a rhombohedral crystalline structure. The crystalline material comprises atoms covalently bonded to form 5 atom thick sheets (in order: Te-Sb-Te-Sb-Te), with sheets held together by van der Waals attraction. Due to its layered structure and weak inter-layer forces, bulk antimony telluride may be mechanically exfoliated to isolate single sheets. Synthesis Although antimony telluride is a naturally occurring compound, select stoichiometric compounds may be formed by th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterojunction
A heterojunction is an interface between two layers or regions of dissimilar semiconductors. These semiconducting materials have unequal band gaps as opposed to a homojunction. It is often advantageous to engineer the electronic energy bands in many solid-state device applications, including semiconductor lasers, solar cells and transistors. The combination of multiple heterojunctions together in a device is called a heterostructure, although the two terms are commonly used interchangeably. The requirement that each material be a semiconductor with unequal band gaps is somewhat loose, especially on small length scales, where electronic properties depend on spatial properties. A more modern definition of heterojunction is the interface between any two solid-state materials, including crystalline and amorphous structures of metallic, insulating, fast ion conductor and semiconducting materials. Manufacture and applications Heterojunction manufacturing generally requires the use of mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chalcogenide
: 220px, Cadmium sulfide, a prototypical metal chalcogenide, is used as a yellow pigment. A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term chalcogenide is more commonly reserved for sulfides, selenides, tellurides, and polonides, rather than oxides. Many metal ores exist as chalcogenides. Photoconductive chalcogenide glasses are used in xerography. Some pigments and catalysts are also based on chalcogenides. The metal dichalcogenide MoS2 is a common solid lubricant. Alkali metal and alkaline earth chalcogenides Alkali metal and alkaline earth monochalcogenides are salt-like, being colourless and often water-soluble. The sulfides tend to undergo hydrolysis to form derivatives containing bisulfide (SH−) anions. The alkali metal chalcogenides often crystallize with the antifluorite structure and the alkaline earth s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermoelectric Cooling
Thermoelectric cooling uses the Peltier effect to create a heat flux at the junction of two different types of materials. A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other, with consumption of electrical energy, depending on the direction of the current. Such an instrument is also called a Peltier device, Peltier heat pump, solid state refrigerator, or thermoelectric cooler (TEC) and occasionally a thermoelectric battery. It can be used either for heating or for cooling, although in practice the main application is cooling. It can also be used as a temperature controller that either heats or cools. This technology is far less commonly applied to refrigeration than vapor-compression refrigeration is. The primary advantages of a Peltier cooler compared to a vapor-compression refrigerator are its lack of moving parts or circulating liquid, very long life, invulnerability to leaks, smal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bismuth Telluride
Bismuth telluride (Bi2Te3) is a gray powder that is a compound of bismuth and tellurium also known as bismuth(III) telluride. It is a semiconductor, which, when alloyed with antimony or selenium, is an efficient thermoelectric material for refrigeration or portable power generation. Bi2Te3 is a topological insulator, and thus exhibits thickness-dependent physical properties. Properties as a thermoelectric material Bismuth telluride is a narrow-gap layered semiconductor with a trigonal unit cell. The valence and conduction band structure can be described as a many-ellipsoidal model with 6 constant-energy ellipsoids that are centered on the reflection planes. Bi2Te3 cleaves easily along the trigonal axis due to Van der Waals bonding between neighboring tellurium atoms. Due to this, bismuth-telluride-based materials used for power generation or cooling applications must be polycrystalline. Furthermore, the Seebeck coefficient of bulk Bi2Te3 becomes compensated around room temperature, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Materials Today
''Materials Today'' is a monthly peer-reviewed scientific journal, website, and journal family. The parent journal was established in 1998 and covers all aspects of materials science. It is published by Elsevier and the editors-in-chief are Jun Lou (Rice University) and Gleb Yushin (Georgia Institute of Technology). The journal principally publishes invited review articles, but other formats are also included, such as primary research articles, news items, commentaries, and opinion pieces on subjects of interest to the field. The website publishes news, educational webinars, podcasts, and blogs, as well as a jobs and events board. According to the ''Journal Citation Reports'', the journal has a 2020 impact factor of 31.041. The journal family includes ''Applied Materials Today'', ''Materials Today Chemistry'', ''Materials Today Energy'', ''Materials Today Physics'', ''Materials Today Nano, Materials Today Sustainability,'' ''Materials Today Communications'', ''Materials Today Adva ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Germanium Telluride
Germanium telluride (GeTe) is a chemical compound of germanium and tellurium and is a component of chalcogenide glasses. It shows semimetallic conduction and ferroelectric behaviour. Germanium telluride exists in three major crystalline forms, room-temperature α (rhombohedral In geometry, a rhombohedron (also called a rhombic hexahedron or, inaccurately, a rhomboid) is a three-dimensional figure with six faces which are rhombi. It is a special case of a parallelepiped where all edges are the same length. It can be us ...) and γ ( orthorhombic) structures and high-temperature β ( cubic, rocksalt-type) phase; α phase being most phase for pure GeTe below the ferroelectric Curie temperature of approximately 670 K. Doped germanium telluride is a low temperature superconductor. Phase Transition Solid GeTe can transform between amorphous and crystalline states. The crystalline state has a low resistivity (semiconducting at room temperature) and the amorphous state has a high r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GeSbTe
GeSbTe (germanium-antimony-tellurium or GST) is a phase-change material from the group of chalcogenide glasses used in rewritable optical discs and phase-change memory applications. Its recrystallization time is 20 nanoseconds, allowing bitrates of up to 35 Mbit/s to be written and direct overwrite capability up to 106 cycles. It is suitable for land-groove recording formats. It is often used in rewritable DVDs. New phase-change memories are possible using n-doped GeSbTe semiconductor. The melting point of the alloy is about 600 °C (900 K) and the crystallization temperature is between 100 and 150 °C. During writing, the material is erased, initialized into its crystalline state, with low-intensity laser irradiation. The material heats up to its crystallization temperature, but not its melting point, and crystallizes. The information is written at the crystalline phase, by heating spots of it with short (<10 ns), high-intensity |
Intermetallic
An intermetallic (also called an intermetallic compound, intermetallic alloy, ordered intermetallic alloy, and a long-range-ordered alloy) is a type of metallic alloy that forms an ordered solid-state compound between two or more metallic elements. Intermetallics are generally hard and brittle, with good high-temperature mechanical properties. They can be classified as stoichiometric or nonstoichiometic intermetallic compounds. Although the term "intermetallic compounds", as it applies to solid phases, has been in use for many years, its introduction was regretted, for example by Hume-Rothery in 1955. Definitions Research definition Schulze in 1967 defined intermetallic compounds as ''solid phases containing two or more metallic elements, with optionally one or more non-metallic elements, whose crystal structure differs from that of the other constituents''. Under this definition, the following are included: #Electron (or Hume-Rothery) compounds #Size packing phases. e.g. Lav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Compound
In materials chemistry, a binary phase or binary compound is a chemical compound containing two different elements. Some binary phase compounds are molecular, e.g. carbon tetrachloride (CCl4). More typically binary phase refers to extended solids. Famous examples zinc sulfide, which contains zinc and sulfur, and tungsten carbide, which contains tungsten and carbon. Phases with higher degrees of complexity feature more elements, e.g. three elements in ternary phases, four elements in quaternary phase In materials chemistry, a quaternary phase is a chemical compound containing four elements. Some compounds can be molecular or ionic, examples being chlorodifluoromethane () sodium bicarbonate (). More typically quaternary phase refers to exten ...s. References Chemical compounds {{chem-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dopant
A dopant, also called a doping agent, is a trace of impurity element that is introduced into a chemical material to alter its original electrical or optical properties. The amount of dopant necessary to cause changes is typically very low. When doped into crystalline substances, the dopant's atoms get incorporated into its crystal lattice. The crystalline materials are frequently either crystals of a semiconductor such as silicon and germanium for use in solid-state electronics, or transparent crystals for use in the production of various laser types; however, in some cases of the latter, noncrystalline substances such as glass can also be doped with impurities. In solid-state electronics using the proper types and amounts of dopants in semiconductors is what produces the p-type semiconductors and n-type semiconductors that are essential for making transistors and diodes. Transparent crystals Lasing media The procedure of doping tiny amounts of the metals chromium (Cr), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doping (semiconductor)
In semiconductor production, doping is the intentional introduction of impurities into an intrinsic semiconductor for the purpose of modulating its electrical, optical and structural properties. The doped material is referred to as an extrinsic semiconductor. Small numbers of dopant atoms can change the ability of a semiconductor to conduct electricity. When on the order of one dopant atom is added per 100 million atoms, the doping is said to be ''low'' or ''light''. When many more dopant atoms are added, on the order of one per ten thousand atoms, the doping is referred to as ''high'' or ''heavy''. This is often shown as ''n+'' for n-type doping or ''p+'' for p-type doping. (''See the article on semiconductors for a more detailed description of the doping mechanism.'') A semiconductor doped to such high levels that it acts more like a conductor than a semiconductor is referred to as a degenerate semiconductor. A semiconductor can be considered i-type semiconductor if it has ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
P-type Semiconductor
An extrinsic semiconductor is one that has been '' doped''; during manufacture of the semiconductor crystal a trace element or chemical called a doping agent has been incorporated chemically into the crystal, for the purpose of giving it different electrical properties than the pure semiconductor crystal, which is called an ''intrinsic semiconductor''. In an extrinsic semiconductor it is these foreign dopant atoms in the crystal lattice that mainly provide the charge carriers which carry electric current through the crystal. The doping agents used are of two types, resulting in two types of extrinsic semiconductor. An ''electron donor'' dopant is an atom which, when incorporated in the crystal, releases a mobile conduction electron into the crystal lattice. An extrinsic semiconductor which has been doped with electron donor atoms is called an n-type semiconductor, because the majority of charge carriers in the crystal are negative electrons. An ''electron acceptor'' dopant is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
