Germanium monoxide

Germanium monoxide [20619-16-3], GeO, can best be prepared in pure form by heating a mixture of Ge and Ge02, in the absence of oxygen. At temperatures above 7I0°C, GeO sublimes from the mixture and condenses as a glassy deposit in the cooler part of the reaction vessel. Germanium monoxide is stable at room temperature. 

Germanium is not found in its free elemental state because it is much too reactive. For the most part, it is found combined with oxygen, either as germanium monoxide or as germanium dioxide. Also, it is recovered from the ores of zinc, copper, and arsenic and the flue deposits of burning coal. 

Germanium monoxide and germanium dioxide are examples of the elements oxidation states of +2 and +4, as follows ... 

Germanium monoxide is prepared by dehydration of the yellow hydrate, obtained by reaction of GeCl2 with aqueous NH3, or by heating Ge(OH)2, obtained from GeCl2 and water. The monoxide, which is amphoteric, is not as well characterized as Ge02, and disproportionates at high temperature (equation 13.60). 

Germanium Monoxide. Probably the first observation of a monoxide phase of Ge-0 was recorded by Winkler in 1886 (41). Notes on the preparation of precipitated hydrous and anhydrous GeO powders can be found in the study of Dennis and Hulse 42 and are also summarized by Johnson (43). 

Germanium Dioxide. The chemical reaction of oxygen with germanium is similar to the thermal oxidation of silicon which results in the growth of a thin layer of silicon dioxide. As noted above, germanium oxidation is complicated by the formation of an intermediate reaction product, germanium monoxide, which, unlike silicon monoxide, is thermodynamically unstable as a solid and sublimes near its formation temperature (46,47). Therefore, instead... 

Alpha-Ge3N4 is formed on Ge surfaces by a vapor phase reaction and most likely by the nitridation of volatile germanium monoxide whereas (3-Ge3N4 is formed by reaction with incompletely bound germanium in the oxide or at oxide-semiconductor interfaces and requires substantial solid state diffusion of nitridant to effect the conversion. 

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