Hydrogen ultra-pure

Silicon is prepared commercially by heating silica and carbon in an electric furnace, using carbon electrodes. Several other methods can be used for preparing the element. Amorphous silicon can be prepared as a brown powder, which can be easily melted or vaporized. The Gzochralski process is commonly used to produce single crystals of silicon used for solid-state or semiconductor devices. Hyperpure silicon can be prepared by the thermal decomposition of ultra-pure trichlorosilane in a hydrogen atmosphere, and by a vacuum float zone process. 

Germanium was the first crystalline semiconductor in which a number of shallow acceptor and donor complexes were discovered that were unambiguously proven to contain hydrogen. This series of discoveries began in the 1970s when several laboratories conducted research and development efforts with the aim of producing ultra-pure Ge single crystal for radiation... 

Fig. 7. Photothermal conductivity of n-type ultra-pure germanium, showing some hydrogen-oxygen donor and phosphorus transitions. In (b) the subscripts 1,2, and 3 of the D(H,0) symbol stand for transitions originating in the first, second and third shallower-lying ls-state. In (c) P stands for phosphorus.

In a very detailed EPR study, Pakulis and Jeffries (1981) and Pakulis (1983) investigated a large number of ultra-pure germanium crystals that were grown in vacuum or in a hydrogen or deuterium atmosphere. Several of the samples were dislocation free. The sensitivity of EPR was greatly... 

Contrary to silicon, very little work has been done in germanium regarding quantitative hydrogen diffusion or electric field drift studies. Such experiments may be complicated by the fact that ultra-pure germanium becomes intrinsic already at temperatures near 200 K. It would be worthwhile to explore the possibility of using lightly doped germanium for such studies in order to explore Fermi level dependent effects. 

The RCA cleaning was developed at a time where the semiconductor industry was much smaller and the environmental restrictions were not as strict as today. Since then the goal in the development of new processes was to reduce the number of necessary cleaning steps, chemical consumption and waste disposal. Recent improvements in wet cleaning have been very successful in further reducing costs, chemical and water usage. Many advances are based on the use of ozonated ultra pure water (UPW) as a replacement for hydrogen peroxide or even sulfuric based mixtures (Heyns et al., 1999). 

Sulfuric acid/ozone mixture (SOM) to remove organic contamination and growth a thin chemical oxide layer. Under optimized conditions ozonated ultra pure water (UPW) can replace the SOM. The SOM step or ozonated UPW step replaces the SPM (sulfuric acid, hydrogen peroxide, DI water mixture) step. 

Unlike the RDE technique, which is quite popular for characterizing catalyst activities, the gas diffusion electrode (GDE) technique is not commonly used by fuel cell researchers in an electrochemical half-cell configuration. The fabrication of a house-made GDE is similar to the preparation of a membrane electrode assembly (MEA). In this fabrication, Nation membrane disks are first hot-washed successively in nitric acid, sulphuric acid, hydrogen peroxide, and ultra-pure water. The membranes are then coated with a very thin active layer and hot-pressed onto the gas diffusion layer (GDL) to obtain a Nation membrane assembly. The GDL (e.g., Toray paper) is very thin and porous, and thus the associated diffusion limitation is small enough to be ignored, which makes it possible to study the specific kinetic behaviour of the active layer [6],... 

All reactants, unless otherwise stated, were purchased from Sigma Aldrich (97- -%). Trap-by-trap distillation were used for further purifications of organic compounds [53,58,59,61]. Ultra Pure air (containing <1 ppm hydrocarbons) was obtained from Matheson Inc. Carrier gases for GC (hydrogen, helium and air)... 

V.M. Gryaznov, Hydrogen permeable palladium membrane catalysts. An aid to the efficient production of ultra pure chemicals and pharmaceuticals. Platinum Metals Rev. 30(2) 68 (1986). 

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