Germanium densities

Germanium single crystals intended for electronic apphcations are usuaHy specified according to conductivity type, dopant, resistivity, orientation, and maximum dislocation density. They may be specified to be lineage-free unless the specified resistivity is below about 0.05 H-cm. Minority carrier lifetime and majority carrier mobHity are occasionaHy specified. 

Analysis of refined germanium products is done in a wide variety of ways, including several methods that have become ASTM standards (47). Electronic-grade Ge02 is analyzed using an emission spectrograph to determine its spectrographic purity. Its volatile content is measured in accord with ASTM F5 and its bulk density with F6. Other ASTM standards cover the preparation of a metal biHet from a sample of the oxide (F27), and the determination of the conductivity type (F42) and resistivity (F43) of the biHet. 

Ni [182], V [183], and A1 [184]. SU-M [185] is a mesoporous germanium oxide with crystalline pore walls, possessing one of the largest primitive cells and the lowest framework density of any inorganic material. The channels are defined by 30-rings. Structural and thermal information show that there exists a mismatch between framework stability and template decomposition. The latter requires temperatures higher than 450 °C, while the structure is preserved only until 300 °C. 

It can be seen from Fig. 14.7 that the polarization curve for this reaction involving p-type germanium in 0.1 M HCl is the usual Tafel straight-line plot with a slope of about 0.12 V. For -type germanium, where the hole concentration is low, the curve looks the same at low current densities. However, at current densities of about 50 AJvcF we see a strong shift of potential in the positive direction, and a distinct limiting current is attained. Thus, here the first reaction step is inhibited by slow supply of holes to the reaction zone. 

The diamond-type structure of a-tin is stable at ambient pressure only up to 13 °C above 13 °C it transforms to /J-lin (white tin). The transition a-Sn —> /J-Sn can also by achieved below 13 °C by exerting pressure. Silicon and germanium also adopt the structure of p-Sn at higher pressures. The transformation involves a considerable increase in density (for Sn +21%). The J3-Sn structure evolves from the a-Sn structure by a drastic compression... 

Fig. 12. Derivative curves of EPR in a highly dislocated As-doped germanium crystal grown in a H2 atmosphere. The magnetic field is oriented along the [100] direction. T= 2 K, /= 25.16 GHz. Note the sign reversal of the new lines as compared to the As-donor hyperfine structure. Dislocation density 2 x 104 cm 2. (Courtesy Pakulis and Jeffries, reprinted with permission from the American Physical Society, Pakulis, E.J., Jeffries, C D. Phys. Rev. Lett. (1981). 47, 1859.)...

The triaryl radicals of germanium exhibit lower g values than their trialkyl counterparts. In part, this arises from increased delocalization of the unpaired spin density onto the aryl rings (and the Ar3Ge radicals do show hyperfme coupling to the ring protons). For example, spin densities for the radicals PhmMe3 mGe, calculated by the Hiickel method (Table 2), reveal that there is a linear correlation between the g value of the radical and... 

A traditional object for testing new methods is germanium. The ehemieal bonding in Ge was studied by X-ray diffraction, Hartree-Fock methods and density functional theory for which good agreement of electron densities was reached. Hence the ESP calculated from eleetron diffraction were also compared with the above results obtained from other methods. 

Avilov, A.S., Eepeshov, G.G., Pietseh, U., Tsirelson, V.G. Multipole Analysis of the Electron Density and Eleetrostatie Potential in Germanium by High-resolution Eleetron Diffraetion. J.Phys.Chem.Solids. (2001), 62, 2135. 

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