Germanium surface chemistry

The existing literature on reactions at germanium surfaces under vacuum conditions is not as extensive as that of silicon. However, germanium surface chemistry is an 

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Several excellent reviews are available concerning both surface structure of semiconductors and surface chemistry of semiconductors, including Refs. [5-23]. Here, a comprehensive review is not attempted and the reader is referred instead to those references. The focus of this chapter is primarily on the surface chemistry of silicon and germanium, as these are the two most heavily studied systems. We strive to provide insight into the chemical reactivity of these two surfaces, and hence... 

In addition to Grignard chemistry and hydrogermylation, for which analogs also exist for silicon, there is another type of functionalization chemistry that has been carried out on germanium surfaces that of alkanethiol attachment to H-terminated Ge. Alkanethiols are well known for their use in self-assembled monolayers (SAMs) on gold surfaces. 

Buriak, J. M. Organometallic chemistry on silicon and germanium surfaces. Chemical Reviews 102, 1271-1308 (2002). 

Loscutoff, P. W. and Bent, S. F. Reactivity of the germanium surface Chemical passivation and functionalization. Annual Review of Physical Chemistry 57, 467 (2006). 

Possible choices of semiconductor material for the SPICE design include gallium arsenide, silicon, and germanium. In the work described here, silicon was chosen as a reflection of its commercial importance, however this choice brings with it materials compatibility issues and surface chemistry complications. Silicon has a native oxide SiC>2 that is typically 2 nm thick which makes an inefficient spin injection tunnel barrier. 

These expressions have been used to interpret the capacitive data on germanium, though it proved difficult in practice, on this material, to control the surface chemistry adequately [19]. 

In conclusion Si etching is essentially controlled by the surface chemistry and diffusion of fluorine through the overlayer, as in the previous example, whereas germanium etching depends mainly on the fluorine flux with a weak effect of the surface chemistry. 

Buriak JM (1999) Organometallic chemistry on silicon surfaces formation of functional mono-layers bound through Si-C bonds. Chem Commun 12 1051-1060 Buriak JM (2002) Organometallie ehemistry on silicon and germanium surfaces. Chem Rev 102 1272-1308... 

Buriak JM (2002) Organometallic chemistry of silicon and germanium surfaces. Chem Rev... 

The mesoporous forms of germanium that derive from the above chemistry are very air sensitive and rapidly convert to germanium suboxides GeOx upon exposure in air for a short time (<1 min). This is expected since almost all Ge atoms of the framework lie at or near the surface and the Ge-Ge bond is susceptible in oxidation. The formation of GeOx involves the conversion of Ge-Ge bonds to Ge-O-Ge moieties and seems to be a homogeneous process. This causes a systematic blue-shift of the energy band gap, possibly due to the size-confinement effect. 

In the following section, we provide a brief review of the structures of the major semiconductor surfaces for which the adsorption and reaction chemistry will be covered in this chapter. This includes the (100) and (111) crystal faces of silicon and germanium. Chapter 1 of this book also provides a brief overview of the structure of the silicon surface. The surface structures of compound semiconductors, including GaAs and InP, can be quite complex and are not covered here. A number of reviews describe the structure of these surfaces much more extensively [5,6,25-29], and the reader is referred to those references for more detail. 

Despite the range of hydrides present, hydride termination by HF etching stabilizes the surface against oxidation and maintains surface ordering for further wet chemistry. Hydride-terminated germanium shows no oxidation after exposure to ambient... 

Non-aqueous synthetic methods have recently been used to assemble mesoporous transition metal oxides and sulfides. This approach may afford greater control over the condensation-polymerization chemistry of precursor species and lead to enhanced surface area materials and well ordered structures [38, 39], For the first time, a rational synthesis of mesostructured metal germanium sulfides from the co-assembly of adamantanoid [Ge4S ()]4 cluster precursors was reported [38], Formamide was used as a solvent to co-assemble surfactant and adamantanoid clusters, while M2+/1+ transition metal ions were used to link the clusters (see Fig. 2.2). This produced exceptionally well-ordered mesostructured metal germanium sulfide materials, which could find application in detoxification of heavy metals, sensing of sulfurous vapors and the formation of semiconductor quantum anti-dot devices. 

Hydrogermylation chemistry has been employed to make germanium-carbon bonds at surfaces via the reaction of alkynes and alkenes with the Ge-H bonds of HF-treated surfaces. Recently, this method has also been employed to functionalize the surface of germanium quantum dots (Figure 2). 

The term semiconductor covers a wide range of materials, including the elements silicon and germanium, and compounds such as oxides, sulphides, selenides, etc. A survey of the physics and chemistry of semiconductors is given in the book edited by Hannay and particular reference to semiconductivity and adsorption on oxide surfaces is to be found in an article by Gray . 

Germanium [7440-56-4] M 72.6, m 937 , 925-975 , b 2700 , d 4 5.3. Copper contamination on the surface and in the bulk of single crystals of Ge can be removed by immersion in molten alkali cyanide undCT N2. The Ge is placed in dry K and/or Na cyanide powder in a graphite holder in a quartz or porcelain boat. The boat is then inserted into a heated furnace which, after a suitable time, is left to cool to room temperature. At 750°, a 1mm thickness of metal requires about Iminute, whereas 0.5cm needs about half hour. The boat is removed from the furnace, and the solid samples are taken out with plastic-coated tweezers, carefully rinsed in hot water and dried in air [Wang J Phys Chem 60 45 1956, Schenk in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 712 7963]. Care with the use of cyanide. 

Surface Organometallic Chemistry on Metals Selective hydrogenation of citral on silica supported Rhodium modified by tetra-n-butyl Germanium, Tin and Lead. 

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