Hydride gases

As described above, the precursors traditionally employed for preparation of III-V films have been group 13 metal alkyls (Me3Ga, Me3Al, Me3In) in combination with the group 15 hydride gases (Table 2). These are available on a commercial scale and have appropriate vapor pressures for both atmospheric pressure and low-pressure applications. 

Hydride Generation [9]. The hydride generation technique is probably the most sensitive for direct ICP-AES measurement/detection (Figure 2.17). The sensitivity of this procedure is 50 to 300 times greater than that by direct nebulisation. The method is relatively free from interferences, as it involves separation of the metals as hydride gases from the sample solution after reaction with sodium borohydride in the presence of acid. The technique is limited to the elements As, Bi, Ge, Pb, Se, Sb, Sn and Te, which are known to form readily volatile covalent hydrides. The hydrides are purged directly into the plasma where they are atomised, excited and measured by ICP-AES in the normal way. 

VIL2.2.2 Other thorium hydride gases, ThH2(g), ThH3(g), ThH4(g)... 

Metallorganic chemical vapor deposition (MOCVD) is now widely used in the preparation of III-V and II-VI devices. In addition to the hydride gases used as source materials in other CVD systems (e g., arsine and phosphine), less toxic liquid alternatives (e.g., tertiary butyl arsine and tertiary butyl phosphine) are also used in MOCVD systems along with other toxics such as cadmium alkyls and mercuiy.[42][43]... 

Gallium, like boron, forms a dimeric hydride, Ga-Hi, from which a series of tetrahydrogallates. conlaining the GaHj ion. is derived. 

Continuous, batch, and flow injection modes of hydride generation have been used successfully [39-41]. In the commonly used continuous mode the sample and sodium borohydride solutions are pumped by using a dual-channel peristaltic pump into a mixing chamber. The volatile hydride gas and hydrogen are carried into the plasma with a flowing argon gas and the excess liquid is directed to the drain. 

Works on increase of an overall performance of HHP were simultaneously carried out. For example, in [2] a number of the factors influencing specific output power of HHP has been considered. Properties of metal hydrides (absorbing ability, speeds of reactions, porosity of a covering, the characteristic of a heat transmission of a hydride bed) were analyzed for optimum selection. It has been shown that in pressings from powder metal hydrides gas permeability and effective specific heat conductivity of a bed Xes should be in common optimized in the certain range of a weight share of an additional heat-conducting material. 

HGAAS requires samples that can be transformed into a hydride gas by chemical reaction in an atomiser. Sodium tetrahydroborate is often used as the reducing agent. 

Hydride (gas) purification module These modules generally provide for in-system purifiers, such as resin purifiers and vacuum pumping (for leak checking and purging). 

ZnSi03 ZINC METASILICATE 1837 ZrHIg] ZIRCONIUM HYDRIDE (GAS) 1872... 

The planned use of metal hydride gas gap thermal switches in the compressor beds of the Planck sorption cryocoolers [81,86,88] was briefly mentioned in Section... 

Arsine is a colorless hydride gas (AsHg) formed when arsenic comes in contact with hydrogen or with reducing agents in aqueous solution. Typically, exposure to arsine gas occu rs i n smelting operations or other industrial settings when arsenic-containing ores, alloys, or metallic objects come in contact with acidic (or occasionally alkaline) solutions, and newly formed arsine is liberated. Arsine is also used as a dopant in the microelectronics industry. 

Erlenmeyer returned to the same subject early in 1864. "We can imagine," he wrote, that the four equivalents of a single carbon atom (e.g., in methane, which he now depicted as four vertically arrayed CH groups gathered by a large bracket) have affinity units of intrinsically varying attractive power. Perhaps the reason "methyl" gas and "ethyl hydride" gas, both possessing the identical empirical formula are distinct (as chemists then believed that they were) may be because their two carbon atoms are connected by different sorts of affinity units in the two cases. (This idea had been broached by Butlerov as early as 1861.)... 

Toxic effects may be classified by the nature of the hazard expressed (e.g., irritation), the timing of the resultant effects (eg., acute toxicity), the chemistry of the toxic agent (e.g., hydride gas), the intended use of die agent (e.g., acid etchants), or the mechanism of toxic action (e.g., red blood cell hemolysis). No classification system is any more correct than another, and the system utilized usually depends on the subjects and/or the agents under discussion. This discussion does not attempt to cover all known toxic effects, but rather generally addresses those toxic effects associated with chemicals foimd in plasma etching processes. 

Systemic Toxicity. Systemic toxicity refers to toxicity manifest in biologic tissues other than the tissues of contact with the offending agent. Absorption, at a minimum, must occur for systemic toxicity to exist distribution, metabolism, and/or excretion may also be involved. An example of systemic toxicity in which only absorption is involved is the red blood cell breakage (hemolysis) caused by the hydride gas arsine this hemolysis and subsequent anemia affect the central nervous system, the liver, and the kidneys. For most systemic toxins, a threshold level of agent must be reached before toxicity is manifest this threshold often represents the capacity of the body s defense mechanisms. With two general exceptions. 

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