Germanium metal deposition

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). 

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

The adsorption of albumin from aqueous solution onto copper and nickel films and the adsorption of B-lactoglobulin, gum arabic, and alginic acid onto germanium were studied. Thin metallic films (3-4 nm) were deposited onto germanium internal reflection elements by physical vapor deposition. Transmission electron microscopy studies indicated that the deposits were full density. Substrate temperature strongly Influenced the surface structure of the metal deposits. Protein and/or polysaccharide were adsorbed onto the solid substrates from flowing... 

Fig. 1.2 Oscillations of weight in some non-stationary chemical film systems (1) Alumina sample in cryolite melt with Si02 additives (2) germanium metal in the molten mixture KF-NaF-K2GeF6-Ge02 and (3) fresh cathode deposit of germanium in the melt as in the case 2...

It seems likely that such ion-semiconductor systems are rare in ionic melts due to the degeneracy of the semiconductor at high temperamres. However, some data evidence their formation at some peculiar conditions in course of Si metal deposition out of a KF-KCI-K2S1F6 melt. It was shown [17] that the initial parts of polarization curves contained the non-diffusion waves similar to that observed for germanium systems (see Chap. 3) on a platinum electrode. The same surface waves were detected on Ag and Au electrodes as well, thus suggesting the reduction... 

The second technique is that of transmission spectroscopy through transparent electrodes. The principle of this technique is the same as that of absorbtion spectroscopy whereby if an absorbing substance is present in the diffusion layer near a transparent electrode its spectrum could be recorded in the usual way. The problem with this technique is obviously the need for a transparent electrode. Germanium and doped tin oxide can be used, as can a very thin layer of metal deposited on glass or silica plates. The thin layer can be reduced to a grid which will give conductance to the surface of the plate without making it too opaque. 

In both cases the electrodes were intentionally made very thin, without binders or conductive additives, so that the intrinsic properties of nanostructured materials could be measured. Electrode substrates were prepared by first roughening the surface of the stainless steel plates (to be used as the spacers in 2016 coin cell) using 400 grit sandpaper. A thin nickel/copper coating ( 100 nm) was then evaporated on the surface and finally, the silicon/germanium was deposited directly onto the metal-coated planar substrate. 

Germanium difluoride can be prepared by reduction (2,4) of GeF by metallic germanium, by reaction (1) of stoichiometric amounts of Ge and HF in a sealed vessel at 225°C, by Ge powder and HgF2 (5), and by GeS and PbF2 (6). Gep2 has been used in plasma chemical vapor deposition of amorphous film (see Plasma TECHNOLOGY Thin films) (7). 

This chapter is a review of the CVD of non-metallic elements and covers boron, silicon, and germanium. Silicon and germanium are borderline elements with metalloid characteristics. Both are important semiconductor materials, particularly silicon, which forms the backbone of the largest business in the world the electronic industry. All three materials are deposited by CVD on an industrial scale and a wide variety of CVD reactions are available. 

The metal alloy, niobium germanium (Nb3Ge), is another superconductor with a much lower transition temperature (20K) with well-established characteristics and good strength. It is deposited by CVD on an experimental basis by the reaction described in Ch. 6. 

Porter LA, Choi HC, Ribbe AE, Buriak JM (2002) Controlled electroless deposition of noble metal nanoparticle films on Germanium surfaces. Nano Lett 2 1067-1071... 

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