Germanium metals

The physical, thermal, and electronic properties of germanium metal are shown in Table 1. Optical properties are given in Table 2. 

AH intrinsic germanium metal sold is specified to be N-type with a resistivity of at least 40 H-cm at 25°C or 50 H-cm at 20°C. Germanium metal prepared for use in infrared optics is usuaHy specified to be N-type with a resistivity of 4-40 Hem, to be stress-free and fine annealed, and to have certain minimum transmission (or maximum absorption) characteristics in the 3—5 or 8—12 pm wavelength ranges. Either polycrystaHine or single-crystal material is specified. 

The type and resistivity of aH grades of germanium metal are also measured in accord with F42 and F43. The transmission characteristics of... 

Germanium metal is also used in specially prepared Ge single crystals for y-ray detectors (54). Both the older hthium-drifted detectors and the newer intrinsic detectors, which do not have to be stored in hquid nitrogen, do an exceUent job of spectral analysis of y-radiation and are important analytical tools. Even more sensitive Ge detectors have been made using isotopicahy enriched Ge crystals. Most of these have been made from enriched Ge and have been used in neutrino studies (55—57). 

Germane is used primarily to produce high purity germanium metal or epitaxial deposits of germanium on substrates for electronics by thermal decomposition at about 350°C (see Germaniumand germanium compounds). 

Considerable interest in the sohd-state physics of sihcon carbide, that is, the relation between its semiconductor characteristics and crystal growth, has resulted from the expectation that SiC would be useflil as a high temperature-resistant semiconductor in devices such as point-contact diodes (148), rectifiers (149), and transistors (150,151) for use at temperatures above those where sihcon or germanium metals fail (see Semiconductors). 

Compounds with Germanium-Metal (or Metalloid) Bonds 748... 

The preparation of resolved species which are chiral at the germanium metal center have been reported (Equation (37), Table 2)44 47 as have species containing biologically important ligands48-52 including derivatives of a-amino-phosphonic acid.48-50... 

The triphenylmethyl-substituted germanium halide 31 can be prepared in modest yield using GeCl4 and contains a formally seven-coordinate germanium metal center (Scheme 9). The structure of 31 (Figure 2, Table 11) is a tricapped tetrahedral structure where all the three Ge-O distances are shorter than the sum of the van der Waals radii (3.62 A). A series of hypervalent germanium halides 32-34 can be prepared, as shown in Scheme 10.95 The fluoride 32 is hexacoordinate, whereas the chloride 33 and bromide 34 are pentacoordinate. 

Germylenes can be released thermally in the presence of a transition metal complex leading to the formation of a germanium-metal bond (Equation (193)).239 The reaction occurs at room temperature when a germylsilane is used as the synthon (Equation (194)).240... 

Chemical Properties of the Germanium-Metal Bond 3.13.7.2.1 Reactions involving cleavage of the Ge-metal bond... 

Silicon and germanium hydrides react with cobalt, manganese and rhenium carbonyls affording complexes having a silicon (or germanium)-metal bond. These reactions, described previously for inactive compounds have been used in the synthesis of optically active silyl and germyl-transition metals ... 

Arts, J.H., Reuzel, P.G., Falke, H.E., and Beems, R.B. Acute and sub-acute inhalation toxicity of germanium metal powder in rats, Food Chem. Toxicol, 28(8) 571-579, 1990. 

Germanium(IV) chloride is prepared by reacting germanium metal with chlorine or by treating germanium oxide, Ge02, with hydrochloric acid ... 

Germanium dioxide is reduced to germanium metal when heated with... 

Germanium dioxide may he characterized hy x-ray methods. Germanium metal may he analyzed in the acidified aqueous extract of the compound by AA, ICP, and other instrumental techniques (See Germanium). 

Monogermane is used to produce high purity germanium metal. It also is used as a doping substance for electronic components. 

The metal film (3-4 nm) thickness on the germanium IRE is approximately two orders of magnitude less than the penetration depth of the electric field and therefore, the germanium, metal, protein/polysaccharide multiphase system can be treated like the "thin film" case described by Harrick (16). 

The insertion of a bivalent metal-14 derivatives into a germanium-metal bond led to polymetal anions which gave, after alkylation, polygermanes (equations 193 and 194)201,202... 

Metal-germene transients are involved after a / -elimination in the chemistry shown in equation 25. The chemistry of equation 25a is a rare example of the direct / -elimination of a silene to result in the germanium-metal bond formation108. 

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